Hybrid Construction – Timber External Walls: Hybrid design: eco-efficient + economic 9783955535766, 9783955535759

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Hybrid Construction  Timber External Walls

Oliver Fischer Werner Lang Stefan Winter

∂ Practice

Editors Oliver Fischer Werner Lang Stefan Winter

Authors Christina Meier-Dotzler Joachim Hessinger Christoph Kurzer Patricia Schneider-Marin Christof Volz

Publisher Editing and copy-editing: Steffi Lenzen (Project management); Claudia Fuchs (Example Builds), Jana Rackwitz (Theory chapters); Signe Decker, Michaela Linder (Editorial Assistance); Sandra Leitte (Proofreading German edition) Cover design following a concept by Kai Meyer, Munich(DE) Drawings: Barbara Kissinger, Irini Nomikou, Sabrina Heckel Translation into English: Raymond Peat, Aberdeenshire (GB) Copy-editing (English edition): Stefan Widdess, Berlin (DE) Proofreading (English edition): Meriel Clemett, Bromborough (GB) © 2022 Detail Business Information GmbH, Munich ISBN 978-3-95553-575-9 (Print) ISBN 978-3-95553-576-6 (E-book) Printed on acid-free paper made from cellulose bleached without the use of chlorine. This work is subject to copyright. The rights arising from this copyright are reserved, especially the rights of translation, reprinting, presentation, extraction of illustrations and tables, b ­ roadcasting, microfilming or reproduction by any other means, and storage in data-­processing systems, either in whole or in part. Reproduction of this work, or of parts thereof, even on an individual basis, is permitted only under the provisions of the copyright law in its current version. This is always subject to remuneration. Infringements are subject to the legal sanctions of copyright law. This reference book takes into consideration the terms valid at the time of the editorial d ­ eadline and the state of the art at this point in time. Legal claims cannot be derived from the content of this book. We assume no ­liability for any errors or omissions. Typesetting & production: Simone Soesters Printed by: Grafisches Centrum Cuno GmbH & Co. KG, Calbe 1st edition, 2022 Paper: Peydur lissé (cover), Magno Volume (content) A German edition of this book is also available (ISBN 978-3-95553-478-3). Bibliographical information of the German National Library The German National Library lists this publication in the German National Bibliography; d ­ etailed bibliographical data is available on the Internet at http://dnb.d-nb.de. Detail Business Information GmbH Messerschmittstr. 4, 80992 Munich, Germany Tel: +49 89 381620-0 detail-online.com

Contents

Foreword    4 Hybrid Construction – Timber External Walls Principles    7 Application and Construction Variants  11 Sustainability   19   22  26

Load-bearing Structure and External Wall Load-bearing Structure Manufacturing and Installation Requirements Interface

  33   36   37   37   41

Building Physics Thermal Insulation Moisture Protection Air and Windtightness Fire Protection Sound Insulation

  49   52   54   56   58   60   62   64   66

External Wall Joints Horizontal Joints – General Requirements and Guidance Floor Slab Joint, Self-supporting Facade; with Services Cavity Floor Slab Joint, Inserted External Wall Elements; no Services Cavity Floor Slab Joint with Access Balcony Base Joint with Timber Bottom Rail beyond the Splash Water Zone Base Joint at Ground Level Flat Roof Joint Vertical Joints – General Requirements and Guidance Firewalls and Firewall Replacement Walls

  70   76   82   86

Example Projects “Aktivhaus” – Multistorey Apartment Building in Frankfurt am Main Experimental Residential Buildings in Wuppertal-Ostersiepen “Ecoleben” – Multistorey Residential Buildings in Penzberg 35 new Subsidised Housing Units in Freising

Appendix   93 Editors and Authors   94 Image Credits  94 Standards   95 Subject Index

Hybrid Construction – Timber External Walls

To tackle climate change, the energyand carbon-efficient use of raw materials and products in construction can play a crucial role in satisfying the urgent need to minimise the emission of climate-­ damaging greenhouse gases. Wood is a construction material with unique properties, not least due to its status as a renewable resource. It has a favourable energy and carbon footprint and can be used for a wide range of purposes in buildings. Timber construction also has advantages for material recycling and energy recovery. Buildings are increasingly assessed using environmental indicators such as primary energy, raw material productivity or greenhouse gas emissions. This assessment is increasingly becoming a part of the building designer’s responsibility, leading to a focus on wood as a building material and its ecological ­qualities. Reinforced concrete is ideal for creating low-cost load-bearing structures that comply with structural and fire regulations for all building classes and work with conventional building services, fire protection and sound insulation concepts. Particularly efficient solutions can result from combining wood and concrete while making the most of their individual advantages and strengths. The realisation of a large number of such projects has shown that hybrid buildings with prefabricated, highly insulated timber facade ­elements and a load-bearing structure with a reinforced concrete skeleton or crosswall construction have much lower energy and carbon footprints than concrete and masonry buildings. This affects not only energy efficiency in the use phase by reducing the operating energy demand, but also makes efficient use of the “grey energy” embodied in the building fabric. 4

Using this type of hybrid construction results in a considerable improvement in the whole life cycle assessment of a building from construction, operation and demolition to reuse, recycling or ­disposal. In addition to the beneficial material properties of wood, the relatively standard construction methods largely based on detachable connections have further advantages when it comes to the eventual demolition of facade components and their recyclability. Highly insulated timber facade elements with comparable thermal insulation properties are much thinner than the corresponding external walls built in concrete or masonry in­­ corporating additional thermal insulation. This increases the usable floor area of these buildings. In addition, the high degree of prefabri­ cation means they are quicker to build – usually without scaffolding – which can mean a shorter construction time and substantial cost savings compared to trad­itional concrete and masonry buildings. This combination of timber facade elements with a concrete load-bearing structure offers timber fabricators and mainstream construction companies who have previously worked exclusively on concrete construction an opportunity to widen their fields of activity in the building market. By working closely together and increasing standardisation, both branches of industry can offer clients shorter construction times and better quality. The fact that prefabricated timber facade elements are still used comparatively rarely in Germany in today’s reinforced concrete, steel or mixed construction buildings, despite the advantages mentioned above, may be due to a lack of experience in dealing with “unfamiliar”

Foreword

trades and materials or to knowledge gaps on the part of architects and engi­neers in the areas of sound insulation, fire protection and deformation compatibility. In addition, progress on the development and presentation of typical details for the required detachable connections has been inconsistent. On the basis of German and European building codes and standards, this ­publication therefore provides clear and practical basic knowledge for use in the design, approval and implementation of economically efficient connections between reinforced concrete floors or walls and timber external wall elements. Essential structural and constructional topics, aspects of the necessary sound and thermal insulation as well as fire and moisture protection measures are addressed. While the described technical information, especially fire protection and sound insulation as well as the case studies, relate to the situation in ­Germany in 2019, the information given can be transferred to other contexts and countries as long as individual adjustments are made regarding regionally varying rules and building r­ egulations. Building on this basic theoretical know­ ledge, the reference details of various connection points between timber and reinforced concrete construction contained in this publication are a valuable aid in the design and implementation of hybrid construction in practice.

The information demonstrates how this sustainable construction method can help bring about a significant improvement in the energy demand and CO2 emissions of such buildings or construction methods over their life cycle. This book is based on the research project “Facade elements for hybrid construction. Prefabricated integral facade elements in timber construction for use in new hybrid reinforced concrete buildings” (published in German), which was funded by the Bavarian construction industry. Without the financial support and the ­outstanding collaboration of all the par­ ticipating companies, research bodies and testing institutions, particularly with regard to their knowledge and expertise, these practical guidelines would never have been produced. The editors and authors of this publication would like to sincerely thank everyone involved. Prof. Dr.-Ing. Oliver Fischer Prof. Dr.-Ing. Werner Lang Prof. Dr.-Ing. Stefan Winter

The detailed presentation of successful built examples towards the end of the book contains information on design and construction to assist designers and contractors in implementing their own hybrid construction solutions based on sound technical principles, with the aim of achieving the highest possible quality and defect-free construction. 5

Principles

Patricia Schneider-Marin Christina Meier-Dotzler

Application and Construction Variants At first glance, “hybrid construction” appears a very abstract term. In a gen­ eral sense, it could apply to almost any type of construction that involves a com­ bination of different building materials. A single component, such as a floor slab, can be a form of hybrid construction itself when you consider the waterproof­ ing, insulation and structural layers. However, for the purposes of this publi­ cation, hybrid construction is defined as the combination of a reinforced ­concrete load-bearing structure with a ­non-structural timber panel construc­ tion element facade. The non-structural external wall consisting of timber panel construction elements contributes nothing to the structural ­stability of the building, i.e. it performs no load-bearing or stiffening function for the building as a whole. Wind loads are normally transferred floor by floor into the building’s load-bearing structure. Dead loads can likewise be transferred floor by floor or from wall element to wall element and into the foundations. In building classes 4 and 5, the facade element must be designed to be fire­ retardant (EI 30). In the event of a fire the

load-bearing capability of individual ele­ ments spanning the storey on fire must be ensured (Fig. 22, p. 30). The studies and application examples presented here focus on the German market. Thus, the named regulations refer to the German standards and rules. Wherever possible, reference is made to the requirements on a European level. Construction of the Load-bearing Structure

The load-bearing structure is normally a reinforced concrete skeleton frame or crosswall construction (Fig. 1). Skeleton Frame One of the main advantages of skeleton frame construction is the flexibility it allows for the final floor layout of the building. Only the column grid and the stiffening cores affect the floor plan. By using non-structural walls, the usable floor space can be relatively simply ­reconfigured during the life of the build­ ing. The floor slabs are designed for the average distance between columns and their thickness dimensioned so that disruptive downstand beams are unnecessary. Another advantage of flat slabs is their simpler construction, which in turn results in shorter completion times.

Ventilation ducts and electrical cabling for building services equipment can be fitted directly to the underside of the floor and there are fewer penetrations through structural components to be designed. Transfer of load through indi­ vidual columns, considered to be point supports, requires a higher proportion of reinforcement at the support points, such as increased bending reinforcement in the top of the slab. As a rule, punching shear reinforcement is arranged around the columns. Calculation of overall build­ ing stiffness is more challenging than with crosswall construction because there are only a few stiffening shear walls available, mostly at the stairwell cores and the separation walls between resi­ dential units. Buildings in earthquake zones, for example, require additional measures to ensure structural stability. The stiffening action of the columns can certainly be brought into the calculation but, compared to the performance of shear walls, is relatively inefficient. The overall stiffness of the frame formed by the columns and the flat slabs is con­ siderably less than that of a shear wall. Eliminating the need for punching shear enforcement is one argument for using downstand beams.

1 1

 hree-dimensional computer model T a  Reinforced concrete frame construction b  Reinforced concrete crosswall construction

7

A A B AB C BC

C

A A B AB C BC

A A B AB C BC

C

C

A A B AB C BC

C

A Facade B  Core element C Services cavity 2 a

b

Crosswall Construction Crosswall construction is extremely suit­ able and widely used for residential build­ ings. Structural crosswalls supporting primarily one-way spanning floors acting as continuous beams are characteristi­ cally seen in crosswall construction. The structural system is simple and clear. Reinforced concrete crosswalls forming part of the structural frame separate living areas and provide effective insulation against structure-born sound thanks to their solid construction. Crosswall con­ struction reveals its advantages where the layout of the rooms is likely to change only slightly during the life of the build­ ing. Subsequent reconfiguration of the floor layout is very expensive to imple­ ment. Proof of structural adequacy requires considerably less effort than for a reinforced concrete skeleton frame because the required building stiffness is simply based on ­having an adequate number of structural shear walls. Construction of the Timber Panel Construction ­Elements

Timber panel construction elements have three basic system areas: facade, core element and services cavity (Fig. 2 and 3). These areas of the building system form the non-structural external wall, which is attached to the building’s reinforced concrete load-bearing structure (see “Connecting to the Load-bearing Structure”, p. 9). The timber panel con­ struction elements form the exterior of the building and combine excellent insu­ lating properties with low wall thickness and lightweight construction. The facade (area A) with the core element (area B) provides thermal insulation and protection against moisture. The facade is primarily there to protect against weather and has a considerable influence on the appearance of the building. Facades can be considered as rear-ventilated/venti­ 8

3 a

b

lated or non-rear ventilated. A compact facade constructed using an external thermal insulation composite system (ETICS) provides some of the thermal insulation (Fig.2 a). A ventilated /rear-­ ventilated facade is designed as a type of curtain wall (Fig. 2 b). To use an ETICS in timber construction currently still requires a national technical approval (abZ) in Germany. In accord­ ance with the current Model Adminis­ trative Provisions – Technical Building Rules (MVV TB), there must also be a European Technical Assessment (ETA). The relevant technical rule B 2.2.1.5 in the MVV TB refers to an ETA in accord­ ance with guideline ETAG 004 for the use of European construction products. However, this European guideline, which is also intended to ensure compliance with national building requirements in Germany, refers only to masonry and concrete construction. Nevertheless, ETAG 004 permits timber construction as a departure from an applicable tech­ nical rule, providing the protection goal or level required by building law is achieved just as adequately. Even if the use of an ETICS in timber construction is not yet completely clarified under building law, it has already been used successfully and in accordance with good practice for years. You can therefore rely on the experience of the companies and engi­ neering professionals carrying out the work. The requirements for the use of ETICS in timber construction may differ in other European countries. The core element (area B) is of timber panel construction. It is based on the same principle as timber frame construc­ tion but with a higher degree of prefabri­ cation. In addition to providing thermal insulation and protection against mois­ ture, the core element also transfers loads and acts as sound insulation and fire ­protection. Slender, linear structural mem­

bers consisting of vertical studs, a bot­ tom and a top rail transfer dead loads and horizontal wind loads to the support points (Fig. 4). The space between the studs and rails is filled with void-free insulation. The structural frame is stiff­ ened on both sides by nailed or stapled wood-based material, gypsum fibre­ board or plasterboard boards. This clad­ ding in combination with a waterproofing membrane and adhesive tape ensures the structure is wind and airtight. The services cavity (area C) provides for simple and concealed routing of pipes and cables. If the insulation thickness of the facade and the core element is insufficient to satisfy insulation standards, the services cavity can also be used as an insulation layer for thermal insulation (Fig. 3). Creating the services cavity on site offers several advantages: no pene­ trations for services are required in the airtightness layer of the core element. All services cavities can be easily installed, concealing the fastenings for the external wall elements in a simple way. Sound pro­ tection is also improved. For increased sound protection requirements, a com­ pletely decoupled and free-standing cur­ tain wall is highly recommended, which can further improve sound protection with self-supporting external walls. How­ ever, a decoupled curtain wall involves considerably more installation work. Therefore, it should be checked early in the design phase whether increased sound insulation is required and a free-standing c ­ urtain wall detailed if the calculated ­values are inadequate (see “Sound I­nsulation”, p. 41ff.). Timber panel construction elements, including the facade, lend themselves to being made, with a high degree of prefabrication and accuracy, in the ­factory and then transported to site. This represents a considerable advantage of the method of construction and timber

Principles

Top rail

Cladding

Stud Bottom rail

4

construction in general. Prefabrication goes hand in hand with a short construc­ tion time on site, which increases the cost-effectiveness as well as the quality of this ­construction method. Fabrication in a controlled factory environment is not affected by changes in weather con­ ditions. The use of floor-height prefab­ ricated timber facade elements has become very widespread.

Cladding

Connection Self-supporting Suspended Inserted Vorgestelltes Vorgestelltes Vorgestelltes Vorgehängtes Vorgehängtes Vorgehängtes Eingestelltes Eingestelltes Eingestelltes variants Außenwandelement external wall element external wall element external wall element Außenwandelement Außenwandelement Außenwandelement Außenwandelement Außenwandelement Außenwandelement Außenwandelement Außenwandele

Connecting to the Load-bearing Structure

Three common forms of connections are available for attaching the timber panel construction elements to the reinforced concrete load-bearing structure: self-­ supporting, suspended and inserted (Fig. 5). They differ from one another in their ­position and the way they transmit loads. The connection types put different demands on the fastening elements and involve different installation sequences. Attachment is generally done using steel angles with bolts and anchors. Further information can be found in “Load-bearing Structure and External Wall” (p. 19ff.) and “External Wall Joints” (p. 49ff.). The con­ nection types have different effects on the building physics characteristics in the area around the connection. In the case of the self-supporting type, the external wall is set forward from the load-bearing structure. The dead load (vertical force) of the external wall is transferred at the base of the individual element into the contiguous floor slab below or via the individual wall elements down to the foundation. This variant ­represents an optimum solution with respect to thermal insulation because the insulation layer is not interrupted. At the same time, it places greater demands on sound insulation and fire protection. For example, the transmission of flanking sound must be prevented by suitable measures (see “Fire Protection”, p. 37ff. and “Sound Insulation”, p. 41ff.).

System

• Stand-alone system in its own plane outside the building structure

• Stand-alone system in its own plane outside the building structure

• Single-span system, floor by floor within the extent of the building structure

Advantages

• Larger tolerance capacity, can compensate for ­dimensional deviations • Continuous insulation skin with almost no thermal bridges • Easy to install the airtight vapour barrier

• Vertical studs do not ­ need to be checked for buckling • Continuous insulation skin with almost no thermal bridges • Easy to install the airtight vapour barrier

• Structural frame members can be integrated within the facade • Reduced secondary sound transfer paths • Fire propagation paths ­interrupted by solid ­structural members

Disadvantages

• Increased construction ­effort to comply with sound insulation and fire protection requirements

• More complex proof of compliance with sound ­insulation and fire protec­ tion requirements • Connections are more complex in comparison to alternative facade types

• System sensitive to ­settlement • Larger gaps at the struc­ tural frame for installation reasons • Increased risk of thermal bridges • More difficult to install the airtight vapour barrier

5

2

3

Wall constructions a  Compact facade and core element b Ventilated or rear-ventilated facade and core ­element Wall constructions a Core element with a directly connected ­services cavity b Core element at a distance from self-­

4 5

supporting services cavity  onstruction of a timber panel construction C ­element Summary of the advantages and disadvantages of the connection variants of non-structural facade elements and an idealised structural system for permanent and variable loads (red = position of gap/joint, attachment)

9

The suspended timber panel construction element facade can also be positioned in front of the load-bearing structure and is suspended floor by floor at the wall head from the reinforced concrete slab above. Unlike the self-supporting variant, the suspended facade is not at risk of the vertical studs buckling. However, the design of the connection points is more complex as a consequence. In the case of the inserted type, the cen­ tral vertical axis of the external wall ­element is almost in line with the front edge of the floor slab and the elements are installed floor by floor directly on the reinforced concrete slab below. This has advantages in connection with the reinforced concrete structural frame because the load-bearing columns can be integrated into the external wall ­construction if ­necessary. In addition, the required level of sound insulation and fire protection is easier to achieve because the degree of integration inher­ ently prevents direct propagation paths, such as through party walls. The degree of integration of the c ­ olumns can be var­ ied to improve sound insulation and fire protection within the bounds of what is structurally achievable. At the same time, this form of construction can be disad­ vantageous in terms of thermal insulation because of possible thermal bridges. With the inserted type, the installation joints are larger than with the two other external wall types, which has implica­ tions for its installation on site. With all three facade variants, the positive (pressure) and negative (suction) forces arising from wind loads are conducted floor by floor into the reinforced concrete structure.

6 a

b

Areas of Application

In the context of construction engineer­ ing and energy, the form of hybrid con­ struction discussed in this book shows

c

10

itself to be an advantageous combin­ation of a robust structure and a resource-­ conserving, individually designable ­building envelope. Hybrid construction can be used for a wide range of build­ ings, including residential and administra­ tion buildings. The design freedom allowed for the facades is equally wide. In accordance with German building ­regulations, non-structural timber ele­ ments can be erected up to a high-rise building height restriction (top storey floor level ≤ 22 m above the average level of the surrounding ground). This may differ in other countries. In general, this form of construction is advisable, particularly where multistorey buildings must be completed quickly. This applies above all for designs with large external wall surfaces and repetitive facade features in which the use of stand­ ardised facade elements can reduce ­fabrication costs per m2 of external wall. With a well-planned construction pro­ gramme, the structural frame and the facade can be completed more or less in parallel, to the benefit of the total ­construction period. Standardised con­ struction does not mean that facades must be monotonous, on the contrary: design requirements can be met through a wide choice of coloured facade panels, metals, timber cladding and plaster ­systems (Fig. 6). Thus, the construction method is becom­ ing increasingly popular for apartment buildings and represents a good alter­ native to masonry and concrete for urban social housing. This form of construction is also recommended for office buildings. The high standard of insulation and low external wall thicknesses result in a greater usable floor area and pleasant indoor climate. The advantages of hybrid construction show themselves not only in new buildings but also in refurbishments. For example, in refurbishments where

Principles

all non-structural facade elements are removed and the building is upgraded to meet current thermal insulation standards without necessitating any changes to the load-bearing structure. In addition, prefabrication of the timber panel elements requires an integrated and detailed approach to the design in which the architect, structural engineer, building services engineers and contrac­ tors are in contact with one another in the early design stages. Only in this way is it possible to accommodate the different dimensional tolerances in the reinforced concrete and timber components while optimising joint design and construction sequences.

in 1998, 178 countries have endorsed the joint “three pillars model” for sustain­ able development [1]. In accordance with this model, ecology (conservation of resources), economy (economic per­ formance) and society (equal rights, peaceful coexistence, health etc.) must be given equal consideration to ensure, amongst other targets, sustainable build­ ing design and construction. Buildings cannot only make a signifi­ cant qualitative contribution to the econ­ omy, culture and society, they are also highly important in the field of ecology. The energy they use is responsible for approximately 19 % of global CO2 emis­ sions [2]. Furthermore, about 35 % of final energy consumption in Germany can be attributed to the buildings sector [3]. Con­ sequently, the buildings sector has the potential of significant leverage in terms of ecological sustainability – by making more efficient use of energy and raw materials. Life cycle assessment (LCA) offers an effective approach to analyse the environmental sustainability of build­ ings. LCA calculates the energy and resource demand, waste and environ­ mental impacts throughout the life cycle of the building, covering everything from the extraction of raw materials, the pro­

Sustainability The Brundtland Commission of the United Nations (UN) refers to “sustainability” in the following terms: “Sustainable devel­ opment is development that meets the needs of the present without compromis­ ing the ability of future generations to meet their own needs.” Since the UN Conference on Environment and Develop­ ment (UNCED) in 1992 and the Enquete Commission of the German Parliament

Production of interior load-bearing structure End of life of interior load-bearing structure

200 180

Non-renewable primary energy [GJ]

Global warming potential [CO2eq]

Production of exterior elements End of life of exterior elements

160 140 120 100 80 60 40 20 0

7 a

Hybrid construction

Concrete / masonry construction

Energy Efficiency

Since the introduction of the 1st German Thermal Insulation Ordinance in 1977, the requirements for the energy efficiency of buildings in Germany have steadily increased. The result is that “modern” buildings consume increasingly less heating and cooling energy. The German Energy Saving Ordinance (EnEV) 2002 included the provisions of the Heating Systems Ordinance (HeizAnlV) and con­

Ventilation for 50 a Heating for 50 a Hot water for 50 a

3,500 3,000 2,500 2,000 1,500 1,000 500

0 -500

b

duction of building components, the building’s construction and use to its eventual demolition and recycling. Hybrid construction using timber panel construction elements improves the ­ecological sustainability of buildings in several respects. It increases resource efficiency through the use of renewable raw materials and, if designed to be ­disassembled, the possibility to reuse materials and components in material cycles. Highly insulated timber panel ­construction elements contribute to energy savings during the use phase of the building (see “Thermal Insulation”, p. 33ff. and “Energy Efficiency”, below). In addition, hybrid construction has eco­ nomic potential through cost and time savings (see “Economy”, p. 16f.).

Hybrid construction

Concrete / masonry construction

6 Various facade materials a Light-coloured masonry facing, student hall of residence Hanover (DE) 2017, ACMS ­Architekten b, c  Fibre-cement sheets varnished in various colours, Neue Burse student hall of residence, Wuppertal (DE) 2013, ACMS Architekten 7 Comparison of hybrid and concrete /masonry con­ struction based on the example of a multistorey residential building in Penzberg (see e ­ xample project p. 82ff.) a  Global warming potential b  Non-renewable primary energy

11

Buildings of the 2000s

8

100 %

Construction

Operation and renovation

sidered building services systems for the first time, which then allowed the produc­ tion of energy from renewable sources to play an increasing role. In 2020, it was replaced by the GEG (Gebäudeenergie­ gesetz = Buildings Energy Act), following the European Energy performance of Buildings Directive (EPBD), which steadi­ly increases the requirements for the energy efficiency of buildings. Reducing oper­ ational energy demand doubtlessly requires more energy and resources to be used in the construction of buildings, e.g. thicker insulation layers, better ­glazing and more sophisticated building

Dismantling

Time

services (Fig. 8). The energy demand for demolition, which will be more compli­ cated, will be higher, and more material will be sent for recycling or disposal. Despite the higher requirements of the EPBD and GEG, in most cases consider­ ably more non-renewable energy will be consumed during the long use phase of a building than was required to build it. How much more depends not only on the quality of the building envelope but also on the energy supply and user behaviour. The GEG, which came into force on 1 November 2020, is the currently valid law applying to the energy efficiency of

Standard

Requirement

Description

KfW Effizienzhaus 55

QP max. 55 % of QP REF

A building with a primary energy consumption at least 45 % less and an external envelope with 30 % less transmission heat losses than the GEG reference building

H’ T max. 70 % of H’T REF

KfW Effizienzhaus 40

QP max. 40 % of QP REF H'T max. 55 % of H'T REF

KfW Effizienzhaus 40 Plus

As Effizienzhaus KfW 40 Production of electricity from ­renewable energy

Passivhaus

Annual heating energy demand 25 % for self-consumption Further requirements relating to comfort and life cycle

10

12

Primary energy demand (non-renewable) for building operation “Grey” primary energy (non-renewable) for manufacturing and disposal

Plus-energy buildings

Primary energy demand (non-renewable)

Buildings of the 1970s

A building with a primary energy consumption at least 60 % less than and an external envelope with 45 % less transmission heat losses than the GEG reference building KfW Effizienzhaus 40, in which at least 10 kWh/a and m2 living area and 500 kWh/a and residential unit are produced and stored

9

Buildings of the 1960s

Buildings of the 2000s

Plus-energy buildings

buildings in Germany. In addition, there are a whole series of energy efficiency standards, such as the Efficiency House standard by the KfW (Kreditanstalt für Wiederaufbau), as well as the Passivhaus and Aktivhaus standards (Fig. 10). The energy efficiency of buildings is for the most part influenced by the insulation standard and airtightness of the external envelope (floor slab or basement ceiling, external walls, windows, doors and roof). Further factors include the extent of any thermal bridges, the orientation and com­ pactness of the building, the ventilation concept and the quality of the systems providing heating, cooling and hot water preparation (see “Thermal Insulation”, p. 33ff.). In the area of energy efficiency, timber facade elements are particularly advan­ tageous because of their good U-values combined with thinner wall thicknesses than can be achieved in reinforced con­ crete or masonry. It is also the case that they can be produced in environments protected from the weather, are easier to make airtight and generally have fewer thermal bridges. Life Cycle Analysis

The less energy required for building oper­ ation, the more effort and money must be

A building that achieves a ­comfortable indoor climate without a separate heating or air-conditioning system

EU requirement: all new buildings must be NZEB-compliant by the end of 2020. (EPBD) Buildings that cover their low ­energy demand by renew­ able sources and fulfil other ­requirements

 8 G  raph showing non-renewable primary energy demand over the life cycle of buildings of differ­ ent energy standards   9 Proportions of non-renewable primary energy ­demand (PE n.r.) during building operation and “grey” PE n.r. for buildings of different energy standards 10 Requirements beyond those of the GEG ­standard 11 Preparation of life cycle assessments in accor­ dance with EN ISO 14 040 12 Life cycle phases of buildings in accordance with EN 15 978:2011-11; grey highlighted: phases currently included in BNB and DGNB life cycle assessments. Phase D is considered only by DGNB.

Principles

Framework of a life cycle assessment Goal and scope definition

Interpretation

Report

Life cycle inventory

Critical review, if necessary

Life cycle impact assessment 11

put into achieving a high-quality building envelope, e.g. installation of more insula­ tion and taking the necessary care to avoid creating thermal bridges. Highly insulating windows are another require­ ment. As a result of all these measures and increasing energy efficiency, a larger share of the total primary energy demand is shifted to the manufacturing and dis­ posal phases of buildings (Fig. 9). The next question is whether and when this increased expense is paid back in eco­ nomic and ecological terms. Only an anal­ ysis that considers the complete life cycle of a building can answer this question and is able to judge further aspects such as durability or ease of cleaning. This applies as much to the economic aspects, which can be assessed by life cycle costing (LCC), as it does to the ecological charac­ teristics, which can be studied in a life cycle assessment (LCA). These holistic life cycle evaluation methods can be used, among other things, to convey to the client the importance of using ecological build­

ing materials and sustainable energy con­ cepts, as both the environmental impacts and the costs can be assessed holistically over the entire life cycle. EN 15 978 divides the life cycle of a build­ ing into separate phases (Fig. 12). This division clearly delineates the bound­ aries of the sequential and in some cases recurring steps of building manufacture, use and disposal. Life cycle assess­ ments performed as part of certification systems, such as those used by the Ger­ man Federal Ministry of the Interior, Build­ ing and Community (BMI), the Assess­ ment System for Sustainable Building (BNB), or by the German Sustainable Building Council (DGNB) include seven or eight of these phases respectively. All excluded phases are project-specific and difficult to assess with the current ­levels of knowledge. In Germany, data can be obtained from the ÖKOBAUDAT database made available by the BMI [4]. Internationally, other databases are com­ monly used, e.g. ecoinvent.

According to EN ISO 14040, a life cycle assessment consists of four steps. The steps are interdependent and therefore the process is usually iterative (Fig. 11). First of all, the objective and the bound­ aries of the investigation are defined. The sort of questions asked at this stage are: For which target group is the life cycle assessment intended? What system boundaries will be drawn in the evalu­ ation? To which functional unit will the results relate? EN 15 804 requires the selected func­ tional unit to be capable of quantifying the use of a product system, thus en­­ abling comparisons with other product ­systems. This could be, for example, the area of an external wall in different constructions with the same U-value. In a comparative life cycle assessment, the system boundaries must be consistently defined in order to produce robust results. Elements outside the temporal or spatial system boundaries must not be allowed to distort the comparison. Take, for example,

Information about the building’s whole-life carbon assessment

Information about the building’s life cycle

Supplementary information beyond the building’s life cycle

Erection

Use

Disposal

Advantages and loads beyond the system boundaries

C2

Transport

C1

Demolition

B1 B2 B3 B4 B5 Modernisation

A5

Replacement, substitution

A4

Repair

A3

Inspection, servicing, cleaning

A2

Use

Raw material extraction

A1

C3

C4

Landfill

Manufacture

Waste management

D

Construction /  installation

C1– C4

Transport

B1– B7

Manufacture

A4 – A5

Transport

A1– A3

Reuse, recovery and recycling potential

B6  Operating energy demand B7  Operating water demand 12

13

13 a

13 S  crewed in place timber facades can be ef­fec­ tively separated into single material types on demolition. 14 Environmental impact categories in accordance with EN 15 978:2011-11, EN 15 804:2021-08 and ÖKOBAUDAT 15 Usage groups and replacement cycles

b

a comparison of two buildings, one of which has a basement and the other not. The basement may not be ignored if stor­ age rooms in the above-ground storeys are included in the assessment of the basement-less building, when, because of their location, the storage rooms in the building with the basement would not be taken into account. However, if neces­ sary, processes that are the same for all systems can be ignored. An example of this would be the comparison of two detached houses of different construc­ tions (e.g. masonry and timber). A base­ ment may be ignored if its construction (e.g. reinforced concrete) is the same in both cases. The life cycle inventory is drawn up using this approach in accordance with EN ISO 14 040. All inputs (e.g. material, energy) and outputs (e.g. wastes) are quantified and totalled for the life of a product. For buildings, this applies for the multitude of components and processes within the system boundaries. The life cycle impact assessment (LCIA) estimates the potential impact on the environment based on the life cycle inventory. Fig. 14 shows the indicators currently used in Germany. The evaluation, which provides an answer to the questions posed in the first step, can now be performed as the final step in the life cycle assessment. Timber facade elements have a lower greenhouse gas potential than concrete or masonry external walls because wood stores carbon as it grows. Less non-­ renewable primary energy is needed to manufacture the timber facade elements. Moreover, the external walls provide ­better thermal insulation for the same material thickness and thus have a posi­ tive effect on the energy demand during operation of the building. In the case of a direct comparison between an apartment building in concrete or masonry and 14

another apartment building in hybrid ­construction with the same plan config­ uration and wall thicknesses, analysis shows that the better insulation perfor­ mance saves more operational energy in addition to what the manufacturing of the timber facade elements already saved in comparison with to the concrete or masonry walls (Fig. 7 b, p. 11). Recycling Concepts

Construction consumes a major part of energy and raw materials in Germany – every year approximately 90 % of all ­mineral raw materials are used in the manufacture of building components and products [5]. To address this situ­ ation, the construction industry is increas­ ingly embracing recycling concepts based on two different approaches: one is to develop concepts for existing buildings to enable the recovery of raw materials in the case of refurbishment or demolition. Another is to design and construct new buildings that make use of recycled building materials and at the same time ensure the possibility of eventual reuse of all resources incorp­ orated into buildings. The following pages primarily consider concepts for new buildings and the potential of hybrid construction for con­ struction compatible with recycling. The first step is to divide the individual parts of the building into usage groups with corresponding service lives (Fig. 15). This ensures that the individual usage groups can be renewed independently of one another. If, for example, the facade cannot be detached from or is part of the building’s structure, then the facade is almost impossible to replace without affecting the structure. According to this division (Fig. 15), the facade is the building component with the second longest service life after the load-bearing structure.

Hybrid construction can offer advantages in this respect because the usage group “facade” is an element independent of the load-bearing structure. To ensure that components can be replaced in the future, the facade elements must be ­connected to the load-bearing structure in such a way that they can be discon­ nected without a great deal of effort or expense. Some component layers may have longer service lives than others. The actual ­service life of a component or a compo­ nent layer may differ significantly from the average service life because it depends on many factors, not least on the quality of the work on site. For good recyclability, the designer must ensure that the building component layers with shorter service lives can be replaced without damaging other layers with longer service lives. Certification systems for sustainable building, such as the DGNB or BNB ­systems, consider the capacity of build­ ings to be deconstructed and their com­ ponents recycled. In both systems this criterion is assigned to the assessment of technical quality. The DGNB system differentiates between the construction (buildings and components) and material (building materials) levels, whereas the new BNB system differentiates between deconstructability, material separability and recyclability. The connections between usage groups, building components and layers play a decisive role for the construction. Con­ nections must be detachable for effective disassembly and separation by material type: permanent connections between materials that cannot be reused together make this more difficult to achieve. The use of bolted connections between reinforced concrete components of the building structure and timber facade ­elements allows the facade to be very

Principles

easily detached. The facade elements can be taken as whole units to process­ Environmental ­ ing companies or workshops so that impact ­separation of the layers does not need Global to take place on site. The construction warming of the elements determines whether the Breakdown of material groups can be efficiently sepa­ the stratospheric rated and sorted according to type. The ozone layer – ozone hole connections between component layers in the core element and in the services cavity are, as far as possible, nailed or screwed, i.e. detachable. The airtightness Formation of near ground layer can be problematic for recycling: level ozone – summer smog the vapour control membrane is installed using staples, which require some effort Acidification of soils and water, to remove. Self-adhesive tape is used e.g. acid rain in the area of the connections and for sealing the joints between OSB boards, Over-fertilisation where these form the vapour barrier. The of soils and water, e.g. algae blooms tape adheres to the component layers. Compared to cast-in-place concrete or Depletion of abiotic masonry walls assembled on site, sus­ resources (fossil pended facade elements generally have energy carriers) the advantage, apart from the glued con­ nections mentioned, that the layers are Depletion of not permanently bonded together, i.e. abiotic resources they can be cleanly separated and sorted (elements) into material types, even though this may 14 require some effort. In the case of the facade, rear-ventilated cladding has the advantage that it is also attached with detachable connections (screws or clips) and therefore easy to dismantle (Fig. 13). On the other hand, an ETICS (external thermal insulation composite system) is glued on. There are no market-ready, quick and easy methods of removing an ETICS from its substrate and then separating its compo­ nents (insulation, plaster etc.) into various material types. Therefore, the poor sepa­ rability of the layers means the use of an ETICS cannot be recommended from an end-of-life point of view. The possibility of recycling the individual 15 materials is assessed at the material level (end-of-life scenarios). The term used in

Impact category

Abbreviation

Unit

Global warming potential

GWP

[kg CO2 equivalent]

Ozone depletion potential

ODP

[kg R11 equiv.] [kg CFC equiv.] [kg CFC11 equiv.]

Photochemical ozone creation potential

POCP

[kg ethene equiv.] [kg C2H4 equiv.]

Acidification potential

AP

[kg SO2 equiv.]

Eutrophication potential

UP

[kg phosphate equiv.]

Abiotic depletion potential (fossil fuels) for fossil resources

ADPF

[MJ]

Abiotic depletion potential (elements) for non-fossil resources

ADPE

[kg Sb equiv.]

[kg PO4 equiv.]

Interior finishes

5 –10 years

Spatial division

10 –15 years

Services



10 – 20 years

Facade



25 – 30 years

Structure



50 –100 years

Site



> 200 years

15

Renovation 6 % (4 %) Existing buildings 47 % (45 %)

Functional buildings Municipal buildings Commercial buildings 7 % (8 %) Timber houses 17 % (18 %)

16

Timber engineering 1 % (4 %)

Carpentry in new builds 22 % (21 %)

this context is “recycling cascade”, i.e. an evaluation of different end-of-life sce­ narios in descending levels of quality. ­Processes with little energy or manu­ facturing/treatment input that result in equivalent or higher-quality products will be ranked higher than complex ­processes that produce inferior quality products (Fig. 17). The higher-quality ­processes are described as reuse; the lesser-quality processes as recycling. If the material is no longer usable, the final process is called disposal. Because the external wall elements in timber panel construction can normally be disconnected from the building struc­ ture, it would be perfectly possible for them to be refurbished and reused as facade elements. The more likely situ­ ation, however, is that individual compo­ nents, e.g. the facade cladding or core elements, would be reused. Timber as a renewable raw material is ideal for long-term cascade reuse and has crucial advantages in the end-of-life phase, because it can be completely fed

back into the ecological cycle. As wood grows, it binds CO2, which can then remain bound for as long as possible, with the timber from the demolition of buildings being perhaps used as a basic ingredient of wood-based products, recycled and remaining useful for many decades. At the end of the cascade, wood can always provide a source of energy. Hybrid construction allows timber to be used as a material in buildings in cases where fire protection requirements would prevent timber being employed in structural members. Economy

The economic advantages of hybrid ­construction are very difficult to quantify in general terms at present. In Germany, one of the reasons for this is that the tech­ nology is not yet included in the German building cost indices because it has been relatively unknown and has seen limited use up to now. In addition, the material and personnel costs vary much across Europe.

Reduce Actions to reduce waste quantities, damaging impacts on the environment and health or pollutant content Comes before Reuse Products or constituent parts for the same purpose for which they were originally intended Comes before Recycling Treatment of waste to produce products, materials or minerals for the original or a new purpose Comes before Other use In particular, energy recovery and backfilling Comes before Disposal Processes that do not constitute recovery, even if minerals or energy are extracted as a secondary process

17

16

In principle, the economic efficiency of a building method can be guaranteed above all if the chosen type of construc­ tion is matched to the usage require­ ments, and the contractors carrying out the work are sufficiently familiar with the special aspects of the method. The contractors carrying out the hybrid construction discussed in this book are mainly traditional medium-sized com­ panies familiar with the specific regional restraints and requirements. Transport distances play only a small role in the economic efficiency of these buildings. However, greater distances would have an increasingly detrimental effect on their sustainability. Against the background of these restraints and requirements, timber construction continues to show a healthy order book. Fig. 16 shows each sector’s share of ­turnover in 2015 and 2016. Holzbau Deutsch­land, the German timber con­ struction trade association, points to a renewed increase in total annual turnover in its annual industry report 2018. It shows the turnover per employee rising strongly, which indicates a considerable rise in productivity. In 2016, 5,603 out of 29,095 (19.3 %) and, in 2017, 4,605 out of 26,952 (17.1 %) non-residential buildings of timber construction received building permits [6]. This represents a significant market share and shows the performance of ­timber construction companies in that sector of the construction industry (Fig. 16). Although the uses of hybrid construction are not collected separately, the figures make clear that hybrid con­ struction, the combination of concrete and masonry with timber construction, has a high potential and makes use of the economic advantages of both build­ ing methods. The following points illus­ trate the economic advantages of hybrid construction:

Principles

250

Average net cost [€/m2]

200 150 100 50 0

ETICS compact facade 1) U-value = 0.18–0.20 W/m2K

Curtain wall 2) U-value = 0.18–0.20 W/m2K

ETICS compact facade 3) U-value = 0.11–0.12 W/m2K

Curtain wall 4) U-value = 0.18 – 0.20 W/m2K

 omprising mineral fibreboards, mineral wool board insulation cut to fill voids; no services cavity C Comprising external cladding, mineral wool board insulation cut to fill voids; no services cavity 3)  Comprising wood laminated boards with a mineral wool core, cellulose board insulation cut to fill voids; ­decoupled services cavity 4)  Comprising colour-coated fibre cement boards, cellulose board insulation cut to fill voids; no services cavity 1)  2) 

18

• The external walls in timber panel con­ struction can be manufactured in paral­ lel with the building’s structural frame. This results in a shorter construction time and therefore savings in labour costs. In Germany, wage costs, either based on the “Kalkulationslohn (KL)” gross wage including costs of employ­ ment or the “Verrechnungslohn (VL)”, which equals KL plus ancillary costs and profit, for carpenters and masons / concrete operatives is approximately the same, as they are both part of the main construction trade and beholden to the same collective wage agree­ ments. In 2018, these rates were EUR 60.75/h for a typical mason /concrete operative and EUR 61.40/h for a typical carpenter [7]. A timber operative in the factory, where the working environment is constant, can work considerably more efficiently than a mason /concrete operative on site, who has to cope with new logistics challenges and changing weather conditions every day. • Another advantage of fabrication in the factory is the routine working practices, which considerably reduce careless mistakes and guarantee high-quality results. Site damage, which may have cost implications, is kept to a minimum. • Hybrid construction can flexibly accom­ modate projecting or recessed facade features or complex geometries, ­whereas this can lead to considerable additional costs in concrete or masonry construction, e.g. for complicated form­ work costs with concrete construction. However, in hybrid construction, the uniformity of external wall surfaces combined with a simple geometry and identical component make-up also reduces unit prices, which can lead to further cost advantages. • Hybrid construction demands inte­ grated design right from the early ­planning stages. To avoid problems

later during installation, the connection details must be well thought out before the wall elements are fabricated. So from the beginning, this avoids design and construction errors, thus saving time and costs. • Although they are thinner than their c­oncrete alternatives, timber panel ­construction elements have a higher insulation standard. This not only reduces energy costs but also pro­ vides a larger net floor area for the same external dimensions. This can be attractive especially to owners of rental properties. As already mentioned, it is difficult to quote general prices per square metre of external wall because they are highly dependent on the characteristics of the project and the national conditions. Based on an analysis of different German projects, prices per square metre could range from approximately EUR 155 to EUR 220 net in 2018 (Fig. 18). The design of the facade is a major ­influence on pricing. External thermal insulated composite systems (ETICS) are generally cheaper than ventilated facades. Typical insulation materials include mineral wool, wood fibre and ­cellulose. For the German examples, the additional cost of wood fibre com­ pared to mineral wool was between EUR 5 – 8/m2. These prices include the cost of transport but not installation. Installation costs were around EUR 15/m2 net plus cranage costs. Normally, an ordinary site crane (including driver) ­provided by the structural framework ­contractor is used. The services cavity (wall lining) is normally completed on site and designed to suit individual requirements. Delivery and installation of a self-supporting wall lining, clad on one side, costs e.g. EUR 38/m2 (wall thickness 75 mm, mineral wool insulation).

Notes: [1] Enquete-Kommission 1998: “Schutz des Men­ schen und der Umwelt – Ziele und Rahmenbedin­ gungen einer nachhaltig zukunftsverträglichen Entwicklung” [2] Lucon, O.; Ürge-Vorsatz, D.; Zain Ahmed, A.; ­Akbari, H.; Bertoldi, P.; Cabeza, L. F.; Eyre, N.; Gadgil, A.; Harvey, L. D. D.; Jiang, Y.; Liphoto, E.; Mirasgedis, S.; Murakami, S.; Parikh, J.; Pyke, C.; Vilarino, M. V.: Buildings. In: Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment ­Report of the Intergovernmental Panel on Climate Change [Edenhofer, O.; Pichs-Madruga, R.; ­Sokona, Y.; Farahani, E.; Kadner, S.; Seyboth, K.; Adler, A.; Baum, I.; Brunner, S.; Eickemeier, P.; Kriemann, B.; Savolainen, J.; Schlomer, S.; von Stechow, C.; Zwickel, T.; Minx, J. C. (pub.)]. Cambridge / New York 2014 [3] Federal Ministry for Economic Affairs and Climate Action (pub.): Energieeffizienzstrategie Gebäude. ­Wege zu einem nahezu klimaneutralen Gebäude­ bestand. Berlin 2015 [4] Federal Ministry of the Interior, Building and ­Community (BMI): Ökobaudat. http://www.oeko­ baudat.de [5] Deutsches Ressourceneffizienzprogramm ­(ProgRess II). Fortschrittsbericht 2012 – 2015 und Fortschreibung 2016 – 2019. Berlin 2015. www.bmub.bund.de/fileadmin/Daten_BMU/ Download_PDF/Ressourceneffizienz/progress_II_ broschuere_de_bf.pdf; Downloaded 06.02.2016 [6] Holzbau Deutschland – Bund Deutscher Zimmer­ meister im Zentralverband des Deutschen Bau­ gewerbes e. V. (pub.): Lagebericht 2018. Berlin July 2018. www.holzbau-deutschland.de/file­ admin/user_upload/eingebundene_Downloads/ Lagebericht_2018.pdf; Downloaded 07.11.2018 [7] Zentralverband Deutsches Baugewerbe (pub.): Ermittlung lohnbasierter Kalkulationsansätze im Bauunternehmen. Berechnung von Stunden­ verrechnungssätzen für Kalkulation und Stunden­ lohnarbeiten sowie Erläuterungen zum Ausfüllen der Vergabeformblätter 221, 222 und 223. Merk­ blatt. Berlin 2018 Zentralverband Deutsches Baugewerbe (pub.): Rundschreiben vom 04.06.2018 (excerpts). Lohngebundene Kosten. Neuberechnung nach Tarifabschluss. Berlin 2018

16 T  urnover share of the various sectors of the ­German timber construction industry in 2016, previous year’s value in brackets 17 Waste hierarchy in accordance with the EU Waste Framework Directive 18 Average net cost of different external wall ­variants in timber panel construction (author’s chart derived from manufacturers’ information, 2018)

17

Load-bearing Structure and External Wall

Christof Volz Stefan Winter

In addition to the building physics and sound protection requirements, other important aspects in building design include the construction concept and structural adequacy of hybrid construction. The structural engineer prepares design calculations and detailed construction drawings for the reinforced ­concrete structure and the timber panel construction elements. The concrete ­elements require formwork and reinforcement drawings, which show the geometry of all the reinforced concrete components and their reinforcement with an implied construction sequence. Extensive working drawings show the geometry, the ­timber materials used and the connection components for the facade elements. Fabrication of the timber panel construction elements, their transport to site and installation must be planned to ensure a smooth, efficient fabrication process within budget and on schedule. The interface between the load-bearing reinforced concrete structure and the primarily room-enclosing timber panel construction elements is particularly important in the design, because innovative connection details are key to facilitating rapid installation and satisfying the structural engineering requirements.

Load-bearing Structure This chapter discusses the special structural and constructional features of hybrid buildings and how they should be considered during design and construction. Principles of the Structural Design

The design of hybrid buildings is governed by the currently applicable versions of the European standards (Eurocodes). DIN EN 1990 to DIN EN 1999 are the basis for the structural design calculations. The principles of structural design

are set out in Eurocode 0 and in DIN EN 1990. These define the basic terms, which are used universally throughout other material-specific design standards, and the principal requirements for structural stability, reliability, economic efficiency and durability. An important part of Eurocode 0 is the representation of the design concept with partial safety factors and the listing of each situation to be analysed (load combinations). These partial safety factors increase the normative actions or reduce the material strengths to ensure an appropriate degree of safety. Eurocode 0 also describes two basic limit states: the ultimate limit state (ULS) calculation verifies the structural stability, while the serviceability limit state (SLS) calculation ensures that the structure functions properly during the use phase. The serviceability limit state calculation includes a check on the estimated deflection of building components against stipulated maximum values. The format of verification in accordance with Eurocode 0 is as follows: Ultimate limit state (ULS) Ed ≤ Rd Ed = Calculated value of the effect of the actions Rd = Calculated value of the resistance Serviceability limit state (SLS) Ed ≤ Cd Ed = Calculated value of the effect of the actions Cd = Calculated value of the limit for the critical serviceability criterion The verification procedure considers various combinations of actions to calculate the frequency of occurrence of a load during the life of a building component. Permanent, unchanging loads such as self-weight are designated with “G”, while variable, changing loads such as loads

due to building use, wind, snow or earthquakes are designated with “Q”, “S” or “A”. In addition to the accidental action “Earthquake”, there is also an accidental load case “Fire action”. This is used to calculate the effects of heat on building components to verify that the structure can remain structurally stable for a defined fire resistance period. The partial safety factors γG and γQ are chosen to suit the design situation. The various loads are weighted, depending on their prob­ ability of occurrence, with combination factors ψi, because e.g. the simultaneous occurrence of full snow and full live load is improbable. The “permanent and ­transient” design situation is used in the ultim­ate load state (ULS) to verify the structural stability (component design). The “quasi-permanent” action combinations are used for deformation calculations in the serviceability limit state (SLS). The verification of the building components is performed in accordance with the following material-specific European standards: • Eurocode 1: Actions (DIN EN 1991-1-1) • Eurocode 2: Design of concrete ­structures (DIN EN 1992-1-1) • Eurocode 3: Design of steel structures (DIN EN 1993-1-1) • Eurocode 4: Design of composite steel and concrete structures (DIN EN 1994-1-1) • Eurocode 5: Design of timber structures (DIN EN 1995-1-1) • Eurocode 6 Design of masonry ­structures (DIN EN 1996-1-1) • Eurocode 8: Design of structures for earthquake resistance (DIN EN 1998-1-1) • Eurocode 9: Design of aluminium ­structures (DIN EN 1999-1-1) 19

Construction element (CE)

Dimensions WCE x hCE

Studs Solid structural timber (“KVH”) Glued laminated timber (GLT) Stud spacing Standard length

60 –140 mm ≈ 120 – 240 mm 60 –180 mm ≈ 120 – 400 mm 625 / 833 mm 12 – 20 m

Top / bottom rails KVH GLT Standard length

60 –140 mm ≈ 120 – 240 mm 60 –180 mm ≈ 120 – 400 mm 12 – 20 m

Slabs 1

2

There are further parts and national appendices available for each of the listed standards. In addition to the structural verification formats, Eurocodes 1– 9 also set out design rules to ensure a durable and robust structure. Structural and Geometric Design of Timber ­Facade Elements

The section on “Construction of Timber Panel Construction Elements” (p. 8) shows the construction of the timber facade elements. The structural design of the load-bearing core element is discussed below. In addition to the building physics requirements, the core element must be structurally stable; the facade elements are not usually relied upon to guarantee the global structural stability of the whole structure. However, even with non-structural external walls, the vertical loads (selfweight) and horizontal loads acting on them must be considered. The self-­ supporting variant, set forward from the reinforced concrete structure, requires a ­stability check for buckling of the components. Horizontal loads (creating bending and shear) result mainly from wind loads exerting positive and negative pressure (suction) effects and, in some cases, from horizontal loads applied to the panel cross members from anti-fall protection systems. A timber panel construction element ­consists structurally of vertical studs and horizontally arranged bottom and top rails. These main structural elements are primarily manufactured out of solid structural timber with precisely defined product characteristics (commonly referred to as KVH in Germany), if necessary glued laminated timber (GLT) or ­timber beams made from wood-based mater­ials. A minimum cross-section depth of 140 mm is usually required in order for the studs to support vertical and hori20

Slab thickness

zontal loads. The depth of the studs is often greater than required structurally because of the thickness of the insulation layers demanded by the thermal insulation requirements. The studs have to resist mainly bending and normal stresses. The main type of load on the bottom rail is transverse shear from the studs. Timber panel construction elements can, under certain circumstances, also act as lateral bracing to the building. The important components of the timber panels are the required continuous edge ribs, cladding and the connections. In designing the timber panel construction elements, it is important to ensure that the mechan­ical connecting parts (e.g. staples) create a continuous connection between the ribs and the cladding, and that the loads incurred are transmitted evenly into the timber panels. Because of the very different translational stiffnesses of the components (timber panel construction elements and reinforced concrete walls), the use of the timber panels as bracing to the building is the exception rather than the rule. However, the calculation of the contribution of timber panel construction elements to bracing a building is covered in DIN EN 1995-1-1 [1]. The additional rules in the national appendix must be taken into account. The geometric design is influenced not only by the structural engineering requirements, but also by the degree of prefabrication and the installation procedure, (see “Prefabrication”, p. 22 and “Installation Sequence and Methods”, p. 25ff.). The construction phase also needs to be considered. If the elements are being installed using wire rope slings and chains, they may be subject to forces that differ from those in the design calculations for the building (primarily as a result of self-weight). If the timber panel construction elements are transported

1,250 ≈ 2,500 mm 2,500 ≈ 5,000 mm 12.5 –15 mm

horizontally, the effects of tipping them into the vertical position must also be taken into account. Structural and Geometric Design of the Reinforced Concrete Structure

The load-bearing reinforced concrete structure is normally designed as a skel­ eton frame or crosswall construction. The main advantages and disadvantages of these types of construction are discussed in “Construction of the Load-bearing Structure” (p. 7). Reinforcement Thinner floor slabs require more bending reinforcement, as is the case for longer span lengths. As an example, the required amount of reinforcement for the slab edge area (approx. 1 m, without an edge downstand beam) was determined for a slab system (continuous span) that is similar to that given in “Load-­dependent Deformations” (p. 26ff. and Fig. 19, p. 28 and Fig. 20, p. 29). A parametric study (see p. 27ff.) applied a superimposed dead load of 200 kg/m2 and an imposed load of 230 kg/m2 (in accordance with Eurocode 1 Part 1-1 and DIN EN 1991-1 Category A: Residential buildings including separation wall surcharge) and an imposed load of 500 kg/m2 (in accordance with Eurocode 1 Part 1-1 category B, office areas) to 20, 25 and 30-cm thick slabs and evaluated the results. The study showed that doubling the span quadrupled the required reinforcement. In addition to the increased material requirement and the associated increased material costs, the longer span has a corresponding adverse effect on the life cycle assessment. By increasing the slab spans, the other structural elements such as columns and walls are subjected to greater loads, which also calls for more extensive reinforcement (Fig. 4 and 5).

Load-bearing Structure and External Wall

3 a

Deformation In addition to their effects on the reinforcement requirement, slab thickness and span length also influence the deformation of the system. The section on “Load-dependent deformations” (p. 26f.) explains the results of a parametric study on deformation behaviour, which can be drawn upon in determining the principles for the structural design. In this context, it is important that the specified defor­mations can be accommodated by the selected version of the facade system. The deformation of the reinforced concrete structure must not impose strains on the timber panel construction elem­ents in the facade, otherwise the elem­ents may be damaged or their ­functionality – relating to windows in ­particular – restricted. Different Construction Methods for the Reinforced Concrete Structure The reinforced concrete structure can be built in various ways, the most common of which is using in-situ concrete. Before the concrete is poured, the formwork needs to be erected and the reinforcement fixed in place. With the concrete in place and hardened, the result is a monolithic building component. In-situ concrete construc-

b

tion has the advantage that almost any geometry can be achieved. One disadvantage is that, compared to other methods of reinforced concrete construction (e.g. precast concrete), in-situ concrete is usually a more complex on-site activity. However, the approach of using semi-­ finished precast concrete units can save time compared to in-situ concrete construction. Here prefabricated concrete slabs approximately 6 cm thick are lifted into position, which does away with the need for special slab formwork. The slab needs to be supported only to a limited extent during the concreting process and until the concrete has cured. The additional transverse and the complete upper reinforcement layer is put in place on site. Thermally insulated reinforcement couplers for cantilevering building components can be used with both the in-situ concrete construction and the semi-­finished precast concrete unit approaches, because the reinforcement to be anchored is mostly in the additional in-situ concrete layer. Lattice girders are concreted into semi-­ finished precast floor slabs in the factory and mechanically connect the precast units to the upper in-situ concrete layer. The same semi-finished product approach can be used to build twin h = 25 cm, p = 2.3 kN/m2

3 4 5

14

h = 25 cm, p = 5 kN/m2 Required column reinforcement [cm2/m]

2

J uxtaposition of hybrid construction (rear right) and in-situ concrete construction (front left). Both buildings are given a plaster facade (like the building front right) so that the differences ­between them are hardly noticeable. Dimensions of the construction elements in a ­timber panel construction wall Semi-finished elements a  Wall element b  Slab element Required span reinforcement (slab bottom ­reinforcement layer) Required column reinforcement (slab top ­reinforcement layer)

Required span reinforcement [cm2/m]

h = 20 cm, p = 2.3 kN/m2

1

walls, also known as double walls. In this case, two precast concrete leaves are connected by cast-in lattice girders. Concrete is poured into the cavity between the leaves. The two semi-finished versions are shown in Fig. 3. This method of construction is very effective because only locational support is required during concreting. Once in position, the individual elements are joined together by inserted reinforcement cages, thus reducing the on-site formwork and reinforcement tasks to a minimum. The concrete is then poured into the core to create a monolithic building component. Once the concrete is cured, components built using the semi-finished precast unit approach are the equivalent of their in-situ concrete counterparts. Indeed, they are capable of meeting higher requirements, such as for water perme­ ability and smoke exclusion. A major advantage of the semi-finished precast unit approach is the reduced construction time on site due to prefabrication in the factory. One disadvantage is that it is generally not possible to adjust the geometry on site as can be done with in-situ concrete construction. Prefabrication also demands greater attention to planning and design.

12 10 8 6 4 2

14 12 10 8 6 4 2 0

0 3 4

h = 30 cm, p = 5 kN/m2

4

5

6

7

8

9

Span length [m]

3 5

4

5

6

7

8

9

Span length [m]

21

6 a

b

Reinforced concrete structures can be built using precast concrete components without any significant additional in-situ concrete. Balcony slabs and stairwells are often constructed out of prefabricated concrete units. Industrial buildings frequently incorporate a large proportion of precast components. This form of construction proves particularly efficient in the case of regular floor layouts and long spans. Precast pre-stressed concrete hollowcore floor planks can also be used to similar good effect. Because the use of precast concrete components is not particularly common in general building construction, they will not be discussed further here. However, their use in hybrid construction is perfectly possible.

Manufacturing and Installation Requirements The design of prefabricated timber panel construction external wall elements is largely determined by the transport and installation circumstances. The self-weight of the timber walls is not normally – and in particular compared to concrete components – a crucial factor when considering

c

transport and installation. If large glazed elements are installed in the factory, then the transport and lifting loads must be investigated carefully. Defined tolerances are essential, especially when using prefabricated building systems. In close agreement with the contractors and subcontractors, the construction elements and in particular the interface between the timber panel construction elements and the reinforced concrete structure must be designed to ensure problem-free transport, simple installation and a consistent connection system for the components (see “Interface”, p. 26ff.). Prefabrication

Timber panel construction elements are used to best advantage in hybrid construction if they are for the most part ­prefabricated. The support grid and the resulting dimensions of the individual ­elements must be chosen such that ordinary commercially available building materials and formats (e.g. wood-based boards) can be used in their standard dimensions with very little waste. The boards for cladding the facade elements are normally 1.25 or 2.50 m wide, which determines the usual centre-to-­

centre spacing of 0.625 m (and 0.833 m) for timber studs. The cladding should normally extend over at least two bays. Additional studs are required only at the sides of doors and windows, if they are present [2]. Further structural com­ ponents are required if the timber panel construction elements are to be used to brace or stiffen the building. DIN EN 1995-1-1 [3] should be consulted for this. The boards are available in standard heights of up to 3.50 m, and in special lengths of up to 5 m or more. Because ­timber panel construction elements in hybrid construction normally do not have a bracing role, the elements can incorporate horizontal butt joints between boards. The board formats of structural laminated veneer lumber, OSB, plywood and MDF boards as well as gypsum fibreboard and plasterboard fire protection boards match one another, but special formats can be requested from various manufacturers. KVH and GLT elements are normally available in lengths of between 12 and 20 m, which limits the lengths of the top and bottom rails if they are not to contain butt joints. The transport vehicles and lifting equipment used can also limit the possible

6 7 8 9

7

22

Installation sequence of timber panel construction elements: a tower crane positions the external wall element in front of the load-bearing structure. Prefabrication of the timber panel construction ­elements at a timber construction company Maximum permitted dimensions of vehicles and loads in accordance with § 22 StVO Maximum permitted individual vehicle length in accordance with § 32 StVZO, all dimensions in m

Load-bearing Structure and External Wall

manufactured panel sizes. The high degree of prefabrication guarantees a short installation phase, which also ­minimises the danger of moisture penetration during construction. Large elements demand more precise planning of transport vehicles, lifting equipment, lifting tackle and scaffolding [4].

heights for transport within the European Union. The requirements of Directive 96/53/EC must be taken into account for transports within the EU. Whether a proposed oversize transport requires a permit can be determined based on the requirements of the German Road Traffic Regulations (StVO) and the Road Traffic Licensing Regulations (StVZO), which govern the use of vehicles with and ­without loads. The StVO sets out the dimensions of the vehicle and load (load-­ dependent limits), whereas the maximum permitted dimensions of vehicles (vehicle-­ dependent limits) are given in the StVZO. If the transport complies with the limits of both sets of regulations, then it can take place without the need to obtain specific permission. If the limits are exceeded, an exemption is required and the transport may, depending on the federal state, also require a police escort. Therefore, the permitted size of the elements and any potential transport permissions should be considered early in the design of the timber facade elements to avoid possible resulting additional costs. The limits applied to vehicle measurements in accordance with the StVO vary depending on the type of vehicle used.

Transport

The prefabricated timber panel construction elements must always be protected from external influences (weather) during transport to the site for final installation. Compared to other materials such as steel or concrete, wood has a relatively low density / ratio of weight to volume and therefore transport is usually limited by the dimensions of the load rather than its weight. The focus when building with timber panel construction elements is on oversize transport rather than heavy transport, because the overall dimensions are determinant. The following ­paragraphs set out in detail the limiting factors for oversize transport in Germany. Directive 96/53/EC [5] stipulates the maximum permitted transport dimensions of motor vehicles, articulated vehicles and road trains, vehicle widths and

The main limiting factors are generally the height limit for passing under bridges, tunnels and underpasses as well as the general dimensions of the road. In accordance with § 22 StVO, the vehicle and load should not exceed a width of 2.55 m or a height of 4.00 m, while the total length should be less than 20.75 m. Fig. 8 shows the permitted limits for load overhangs. Size-related limits applicable to vehicles and vehicle combinations are listed in § 32 StVZO and correspond with a width of 2.55 m and a height of 4.00 m, the ­limits for a vehicle and its load. In accordance with the StVZO, the vehicle width is measured “(…) with the doors and ­windows closed and the wheels aligned straight ahead” [6], without consideration of “mirrors and other systems for indirect vision” [7]. However, there are limits on vehicle lengths for individual vehicles and for different vehicle combinations. Fig. 8 shows the limits on the length of an individual vehicle given in the StVO. Fig. 9 and 11 (p. 24) summarise the maximum length limits given in the StVZO for road trains (tractor unit and semi-trailer or rigid heavy goods vehicle (HGV) with drawbar trailer) and articulated vehicles.

All dimensions in m

Vehicle or road train incl. load ≤ 20.75

≤ 1.5

≥ 2.5

≤ 4.0

≤ 0.5

without flag with flag, distance > 100 km with flag, distance ≤ 100 km 8

≤ 1.0

≤ 0.4

≤ 1.5

≤ 2.55

≤ 0.4

Individual vehicle length ≤ 12.0

≤ 3.0 9

23

10

≤ 12.0 ≤ 18.75

≤ 16.4 A + B ≤ 15.65 Case A

Case B

≤ 12.0 ≤ 18.75

≤ 2.04

11

24

≤ 12.0 ≤ 16.5

Case A

≤ 15.5

Case B All dimensions in m

A transport that does not exceed these limits can take place without specific permission. If the limits are exceeded, then the transport is treated as an oversize or heavy load. The three most common cases of a transport exceeding a dimensional limit are as detailed below [8]. 1st case: permitted vehicle dimensions exceeded: The vehicle exceeds the vehicle-related limits given in § 32 and 34 StVZO, and makes excessive use of the road. Consequently, this requires permission (driver’s permit) in accordance with § 29 StVO (3) and an exemption for the vehicle in ­accordance with § 70 StVZO, which is generally issued by the relevant local highway authority (e.g. for Munich: the authority for Upper Bavaria). Both documents are required and grant a vehicle­specific permit to use the roads. In ad­ dition, documents indicating the route to be taken and the time window must be submitted [9]. 2nd case: load dimensions exceeded: If the load-related limits for width, height or length set out in § 22 StVO are exceeded, an individual case exception for the load in accordance with § 46 StVO [10] is required. This is granted by the relevant top-level state authority or a legally delegated agency. In considering each individual case, the granting body checks whether the planned route and the submitted transport dimensions would require additional measures. Depending on the dimensions of the vehicle, conditions relating to escort vehicles and/or on-site safety considerations, measures may be imposed for the specific transport requiring approval [11]. 3rd case: combination of case 1 and case 2: In the case of a a transport exceeding both the vehicle and load-­related limits, all of the above-mentioned measures must be considered.

Load-bearing Structure and External Wall

12

Transport type

Max. total weight in acc. with StVZO [t]

Peculiarities and comments

Articulated vehicle

40 1)

Reversing easier

Road train: HGV with trailer

36

Manoeuvrability

Road train: Tractor unit with trailer

24

Lower payload than an HGV with trailer

Road train with low-loader

24

Low ground clearance

1) 

Depending on number of axles

Case 2 is particularly relevant to the transport of timber panel construction ­elements. If the permitted transport width or length is exceeded, the existing carriageway widths and lengths of turning lanes can lead to difficulties and ­considerable additional costs. Take, for example, a traffic lane width of 3.50 m, a total width of transport vehicle of 3 m ­(instead of 2.55 m) and a length of ­overhang of 4.00 m (instead of 3.00 m): exceeding the limits like this also requires, in addition to the exemption, the transport to be accompanied by an escort vehicle or, in certain circumstances, the police on the grounds of traffic safety. The headroom above the road level is normally 4.50 m. This provides for a safety gap of 0.50 m between the vehicle and an engineering structure (e.g. an overpass) [12]. With a minimum safety gap of 0.20 m, the allowable vehicle height can be raised to 4.30 m, which would require special permission. An exception to these rules are engineering structures, including older bridges, with a headroom of less than 4.50 m, which are denoted with signage and ­hazard warning markings in accordance with the “Verkehrsblatt”, the official journal of the German Federal Ministry of Transport and Digital Infrastructure (BMVI) [13]. For oversize or heavy load transports, special low-loaders with a lower loading floor allow for loads with greater dimensions. Planning a transport must take into account the total weight of the freight as well as its dimensions. This is particularly important for semi-finished precast concrete products or precast concrete units. Fig. 12 gives an overview of the permitted total weights in accordance with the StVZO.

Installation Sequence and Methods

Large, flat timber facade elements can be installed in a vertical or horizontal sequence. In practice, installation generally progresses horizontally floor by floor because this quickly results in a series of completed storeys. Fitting out work can commence as soon the storey has been made wind and weathertight. Installation of the facade elements can follow a set time interval behind the progress of the load-bearing structure. If it is more efficient to install the facade elements vertically, the load-bearing structure needs to be at least two storeys ahead of the facade. Vertically sequenced facade elements may be used only for self-supporting facades, whereas horizontally sequenced elements can be used for inserted or self-supporting facades. A detailed site logistics plan is required for the installation. It should allow for ­suitable and capable lifting equipment that can efficiently move the facade ­elements into position. The permitted load of the crane must be adequate to unload the facade elements. This is an important consideration in the choice of a mobile or stationary crane. A conventional site tower crane is often sufficient, but this must be checked for each set of circumstances. When installing the elements, they should not be rotated or tilted into their required installation ­orientation. Horizontally oriented pre­ fabricated elements that are to be lifted from the transport vehicle into position should be transported upright so that they are loaded directly into their final position, without rotation or tilting. Otherwise, this additional manipulation could apply short-term loading transversely to the facade element, which should have been considered as an additional on-site bending load case (with the ­building in its temporary state) alongside

13 a

13 b

10 Drop deck low-loader 11 Maximum permitted lengths of vehicle combi­ nations in accordance with § 32, 1 StVZO: Load train (tractor unit with trailer) in acc. with § 32 ­para. 4.3., 2 StVZO: Load train (HGV with trailer) in acc. with § 32 para. 4.4., 3 StVZO: Articulated vehicle (tractor unit with semi-trailer) considered as cases “A” and “B” in acc. with § 32 ­para. 4.1. + 2 StVZO. 12 Overview of transport vehicles with charac­ teristics 13 Orientation of the large flat timber panel construction elements a  Horizontal configuration b  Vertical configuration

25

helement

belement

14

the main load cases in the design. The fabrication, loading and delivery of the timber panel construction elements should be synchronised with the sequence of installation on site to avoid the requirement for temporary storage space. In addition to the weights and method of supporting the elements, the installation plan should also give details about the slinging points and the fastening elements for lifting in the elements. A horizontal installation orientation of the timber facade elements is advantageous because they can be put in place independently of the planned connection ­variant. The butt joints between the timber panel construction elements are ­designed to transmit force and be airtight to ensure that the joint can fulfil all its structural and building physics functions. The dimensions of the timber panel construction elements should not exceed h element ≈ b element = 3.70 m ≈ 15.00 m in order to ensure smooth delivery and installation, without incurring additional costs. Exemptions for loads issued on an individual case basis can cover dimensions of up to h element ≈ b element = 4.00 m ≈ 16.00 m. Vertically oriented timber facade elements can be used only for the self-supporting variant. The above-mentioned limits to dimensions must also be observed for timber panel construction elements to be installed as vertically oriented. Vertically oriented panels can be used over three to four storeys, depending on the storey height.

Interface The interface between the reinforced concrete structure and the facade elements forms a significant part of the building design. Manufacturing tolerances and load-dependent deformations must be 26

reconciled with one another so that installation can proceed smoothly and efficiently. Manufacturing Tolerances

In the construction of buildings, manu­ facturing tolerances are always to be planned for carefully, because, after manufacture the elements or building components can differ from their intended dimensions, the design dimensions. This difference is known as deviation. The designer must consider how to compensate for these inaccuracies. A permissible variation (tolerance) is specified for the dimension (limit deviation) of the item of the works to be manufactured. Dimensional tolerances can be classified as one of the following tolerance types: •  Manufacturing dimensional tolerances •  Installation dimensional tolerances • Insertion dimensional tolerances or oversize deviation of the on-site construction • Dimension tolerances due to building components changing shape DIN 18 202 specifies the material-indepen­ dent tolerances that must be complied with when building structures in order to allow the building elements of the basic structure and fitting out to be connected without the need for adjustment work after manufacture. The specified normative ­tolerances are based on the accuracy normally achieved in standard practice. Other accuracies can be specified as well. Compliance with higher accuracy requirements leads to higher manufacturing costs and must be technically justifiable. The values for time and load-­ dependent deformations and those for temperature effects are not covered in DIN 18 202 [14] but must also be considered. DIN 18 203-3 contains the manufacturing tolerances for prefabricated timber components. Dimensional tolerances for

angular deviations in length, width and thickness of timber panels are covered by DIN 18 202 (Fig. 16). The manufacturing tolerances for the reinforced concrete structure are in accordance with DIN EN 13 670 and DIN EN 13 369 (Fig. 15). Load-dependent Deformations

The deformation of reinforced concrete components such as slabs and beams, which bend in response to loads, depends on the level of loading. The reason for this is that concrete is highly resistant to compression loads (high compressive strength) but has very low tensile strength and creeps when subjected to long-term compression. In addition to this, concrete shrinks as it cures, which must also be taken into account. The strength of concrete in compression is generally a factor of ten higher than its strength in tension. Therefore steel reinforcement is required to take the ­tensile stresses. In beams, for example, this is provided in the bottom of the section around mid-span. Under light loads, building components loaded in bending are in State I (Fig. 17) because the concrete can resist the tensile stress arising from the load by itself. As the load increases, the concrete can no longer carry the tensile stress by itself and fine cracks form, which have ­insignificant effects on the load-carrying be­haviour. The structural element then ­enters the cracked State II. Cracks in ­reinforced concrete components are nothing unusual. It is only by cracking that the bending element activates the steel reinforcement. A corresponding minimum amount of reinforcement is provided to control the cracks and ensure the appearance satisfies aesthetic expectations. However, the formation of cracks results in an increase in deformations. The deformations in the

Load-bearing Structure and External Wall

Vertical tolerances between beams and slabs

Horizontal tolerances between columns and walls

Openings

± 20 mm

± 20 mm 1) or ± l / 600 max. 60 mm

± 25 mm

l = clearance More stringent values may be required for columns and walls that support prefabricated parts, depending 15 on the length tolerance of the supported component and the required bearing length. 1) 

to the service load. This should be established in close consultation with the client. If in doubt, the bending members must be analysed in the cracked state under the critical load and the analysis must take into account the long-term effects of shrinkage and creep of the concrete, so that, even in this final situation, no strains are imposed on the secondary structural elements. The vertical loads of the facade itself, for example self-weight, fitting out, imposed service loads and their application points represent further input parameters for the calculations. Fig. 18 shows the recommended maximum allowable deformations in accordance with DIN EN 1992-1-1 [15].

Width, height (edge length), opening 16

Design ­dimensions [m]

Limit deviations [mm]

Up to 1.00 m

± 2 mm

Over 1.00 m

± 0.2 % of the ­design dimension maximum ± 5 mm

modern structural engineering software solutions. The increasing variety of numerical modelling techniques available means it is relatively simple to calculate deform­ ations in the cracked State II using the finite element method (FEM). The calculations are routinely carried out for conventional concrete structures and hybrid construction. In order to arrive at reliable deformation tolerances for the reinforced concrete structure, the designer must focus particularly on State II. The results of the calculation must be verified by the structural engineer for the project. Parametric Study

A parametric study [16] that was ­carried out as an aid to the designer evaluates the edge deformation of a slab span. This allows the designer to make a preliminary assessment of whether a proposed column or wall grid will result in acceptable

DIN EN 1992-1-1 also offers the option of precambering the formwork by a max­ imum of l/250 to partially or completely compensate for the eventual sag. A ­max­imum value for the deformation of f ≤ l/500 is recommended for the edges of slabs to which the timber panel construction elem­ents forming the facade are connected. Deformation calculations for the uncracked State I can be performed using the theory of elasticity. Analyses for the cracked State II are increasingly performed using

Deformation [f]

cracked State II are much larger than those in the uncracked State I. Accurate estimates of deformation are difficult to make. Often the normative level of load is not achieved or the material exhibits greater stiffness than the standard predicts. Precise input parameters characterising the individual concrete-specific shrinkage and creep behaviour are also difficult to define for a given set of circumstances. Some scatter applies to these parameters, which means the designer has to rely on limit value considerations. The deformations for State I can be adopted as the lower limit value. The maximum expected deformations are calculated assuming State II. The prob­able deformations will be somewhere between these two limit values. Fig. 17 shows that deformation f based on the input parameters load and the actual material resis­ tances is subject to stochastic scatter and can also increase further during the service life due to shrinkage and creep. Deformation calculations are often based on engineering judgement. The normative load level is usually on the safe side in relation to the imposed load in service. To be able to accurately calculate deform­ ations, the imposed load applied should be the one that most closely corresponds

17

er Upp

limit

14 D  efinition of the dimensions of timber panel ­construction elements 15 Building shell tolerances in accordance with DIN EN 13 670 16 Limit deviations for walls in accordance with DIN 18 202-3 17 Probability of the calculated value of the defor­ mation f shown in relation to time t 18 Recommended maximum allowable deformations in accordance with DIN EN 1992-1-1

e

valu

II) tate re S u p ( alue ly v Like e valu mit li r e Low te I) (Sta

t=0

Time [t] t=∞

18

Determining factor

Maximum sag

Consideration of appearance and serviceability for slabs and beams

l /250

Damage of adjacent components caused by deformations

l /500

27

19

deformations. The floor system was modelled with a free edge and a downstand beam edge, and analysed using the SOFiSTiK 2014 software package. It performs a non-linear analysis for the serviceability limit state with the appropriate load case combinations. In a preliminary calculation (see “Structural and Geometric Design of the Reinforced Concrete Structures”, p. 20ff.), the structurally required reinforcement is calculated and then expressed as a practical arrangement of bars at specified spacings. Shrinkage and creep coefficients are calculated for each set of circumstances. The effective slab width Weff and the bending stiffness of the downstand edge beams were determined in accordance with Grasser / Thielen [17]. The following system parameters were used in each case: • Materials: concrete C25/30, cement CEM32.5N (S), reinforcement B500 • Durability, creep and shrinkage: ­exposure class XC1, cnom = 2.5 cm, RH = 50 %, Loads applied after t0 = 28 d • Permanent loads: gslab = hslab ∙ 25 kN/m3 gfit-out = 2.00 kN/m2 gfacade = hfacade ∙ 2.00 kN/m The following parameters were varied: • System: continuous slab system with free edge and dropdown edge beam • Imposed load 1: pk = 1.50 + 0.80 kN/m2 (in accordance with DIN EN 1991-1 Category A (residential building) including separation wall allowance) • Imposed load 2: pk = 5.00 kN/m2 (in accordance with DIN EN 1991-1 Category B office building) • Span lengths: leff = 4.00 m, 5.00 m, 6.00 m, 7.00 m and 8.00 m • Slab thicknesses: hslab = 0.20 m, 0.25 m and 0.30 m • Downstand edge beam: depth of down28

stand edge beam hd = 2 ≈ hslab Width of downstand edge beam Wd = hslab Effective slab width Weff = leff /6 A total of 80 calculations to determine the deformations was performed. Fig. 20 shows the results, including the limits for the permitted deformation of l/250 and l/500. The deformation behaviour at the slab areas under realistic edge conditions can be derived from the numerical analyses and the calculated deformations then used as design recommendations. The calculated sags cannot be applied everywhere and do not take the place of a formal structural calculation. The centre-to-­ centre distances between columns and walls can be determined based on the results from the various span lengths. The calculated values can be checked against the permitted deformations (l/250, l/500). Because the calculation of deformations was based specifically on the State II cracked section, they can be considered as upper limit values. Attachment of the Timber Panel Construction ­Elements

The timber panel construction elements can be attached to the reinforced concrete structure in various ways. There are three basic connection variants: self-­ supporting, suspended and inserted (Fig. 5, p. 9). The variants differ in the position of the facade elements and the designed vertical attachment points, i.e. the way they transfer their loads. The horizontal support by which they transfer positive and negative wind loads is normally storey by storey, with the connections acting horizontally being designed for the full horizontal load in all variants. In the case of the self-supporting variant, the non-structural external wall stands in front of the load-bearing structure. The

facade elements form an independent, self-supporting component of the building. Vertical self-weight is transferred from element to element into the structure below or into a separate foundation. In the case of the suspended variant, the facade elements are also outside the load-bearing structure. These are ­suspended from the concrete floor slabs ­floor by floor using steel connection elements (mainly steel angles). The inserted variant involves facade ­elements that stand directly on the concrete floor slabs of the load-bearing ­structure and thus lie in the same plane as the end of the load-bearing structure. Vertical load transfer is by contact ­pressure. The timber panel construction elements are placed at the edge of the floor slab without the need for connections to transfer vertical load because this is done by contact pressure. Connections

The load transfer points for the different variants have been explained earlier. The load paths for the suspended and inserted variants are clear in each case. Their design is done on the basis of the actual loads. In the case of the self-­supporting variant, however, the facade self-weight in the determinant design situation (serviceability limit state) is transmitted by contact pressure through the individual elements into the foundation. However, the connections are designed for a horizontal load (wind and crossbeam loads) as well as for a vertical load (facade self-weight). Horizontal loads are applied in full, whereas only part of the vertical load is considered. Despite the intention for the bearings to allow free vertical movement, a vertical bearing force is generated because of frictional resistance. This has been confirmed by tests to determine the displacement stiffnesses at wall-slab connecting elements by the

Load-bearing Structure and External Wall

120

Inner span l/250 l/500 Inner span with downstand edge beam h = 0.20 m, p = 2.30 kN/m2 Sag in State II [mm]

Sag in State II [mm]

End span l/250 End span with downstand l/500 edge beam h = 0.20 m, p = 2.30 kN/m2

100 80 60

60 50 40 30

40

20

20

10 0

0 3

4

5

6

7

8

9

Span length [m]

20 a

3

60 50 40 30

7

8

9

Span length [m]

80 70 60 50 40

20

10

10

0

0 3

4

5

6

7

8

3

9

Span length [m]

c

60 50 40

5

6

7

8

9

Span length [m] Inner span l/250 l/500 Inner span with downstand edge beam h = 0.25 m, p = 5.00 kN/m2

Sag in State II [mm]

80 70

4

d

End span l/250 l/500 End span with downstand edge beam h = 0.25 m, p = 5.00 kN/m2 50 45 40 35 30 25 20

30

15

20

10

10

5

0

0 3

4

5

6

7

8

9

Span length [m]

e

3

100 80 60

5

6

7

8

9

Span length [m]

End span l/250 End span with downstand l/500 edge beam h = 0.30 m, p = 5.00 kN/m2 120

4

f

Inner span l/250 Inner span with downstand l/500 edge beam h = 0.30 m, p = 5.00 kN/m2 Sag in State II [mm]

Sag in State II [mm]

6

30

20

19 Deformed slab system 20 Deformation in State II in relation to the span length a Span length (end span) for a 20-cm thick slab and a 230 kg/m2 live load b Span length (inner span) for a 20-cm thick slab and a 230 kg/m2 live load c Span length (end span) for a 25-cm thick slab and a 230 kg/m2 live load d Span length (inner span) for a 25-cm thick slab and a 230 kg/m2 live load e Span length (end span) for a 25-cm thick slab and a 500 kg/m2 live load f Span length (inner span) for a 25-cm thick slab and a 500 kg/m2 live load g Span length (end span) for a 30-cm thick slab and a 500 kg/m2 live load h Span length (inner span) for a 30-cm thick slab and a 500 kg/m2 live load g

5

Inner span l/250 l/500 Inner span with downstand edge beam h = 0.25 m, p = 2.30 kN/m2 Sag in State II [mm]

Sag in State II [mm]

70

4

b

End span l/250 l/500 End span with downstand edge beam h = 0.25 m, p = 2.30 kN/m2

Sag in State II [mm]

Materials Testing Office for Civil Engineering at the Technical University of Munich (MPA BAU) [18]. Elongated hole connections with sliding layers (Teflon), separating layers for sound decoupling (Sylomer) and the same arrangements without these two materials were tested. A compatibility load factor can be applied to calculate this possible load transfer from the outside wall into the reinforced concrete structure. This compatibility load factor represents the proportion of the external load taken into consideration in the design of the connections. For the quasi-permanent design situation (design in the cold state, not in a fire), the factor sf = 0.5. To cover the fire load case, the compatibility load factor is raised to sf = 1.0, because the fire could cause a vertical load-transferring facade element to fail and the vertical transmission of load through the facade could then no longer be guaranteed. The partial safety factors to be used are shown in Fig. 23 (p. 31). For the accidental fire load combinations, the partial safety factors apply to the permanent and to the vari­ able loads γg = γq = 1.00. The connections of the facade elements above the slabs must be designed floor by floor for their vertical loads. Because

70

120 100 80 60

40

40

20

20

0

0 3

4

5

6

7

8

3

9

Span length [m]

h

4

5

6

7

8

9

Span length [m]

29

Dead weight Dead weight weight Dead facade facade facade

Steel angle Steel angle angle Steel Wood screw Wood screw screw Wood Heavy-duty anchor bolt Heavy-duty anchor bolt bolt Heavy-duty anchor

u2 uu22

u2 uu22

Dead Dead Dead weight weight weight facade facade facade Wind load Wind load load Wind (suction or (suction or or (suction pressure)) pressure)) pressure))

1 31 13 3

·u1 ·u1 ·u 1

2 32 23 3

·u1 ·u1 ·u 1 Z dowel dowel ZZ =Pull) dowel (Z (Z=Pull) =Pull) (Z H dowel H dowel dowel H (H=hearing) (H=hearing) (H=hearing)

u u1 uu uu11

21 a

b

the elements are attached by means of elongated holes, the facade elements may slide down by the amount of the elongated hole clearance but the overall stability of the facade is preserved (Fig. 22). The design of the connections is based on the use of partial safety factors (Fig. 23) and considers both the normal and the fire load scenarios. The (self-supporting or suspended) facade elements are usually attached to the reinforced concrete slabs by steel angles, which are connected by anchors or heavyduty anchor bolts to the concrete load-­ bearing structure and by wood screws to the stud construction of the facade element. A number of options for anchoring the steel profiles are available (Fig. 23). The design of the connection is based on a detailed section (Fig. 21 a) which shows a typical steel profile. Fig. 21 b

22

30

Normal load scenario Normal load load scenario scenario Normal

u uu

D concrete D concrete concrete D (D=pressure) (D=pressure) (D=pressure)

u1 uu11

r­ epresents a simplified static model. The bearing and internal forces in the steel section or angle are calculated using traditional frame analysis. The steelwork design is in accordance with DIN EN 1993-1-1 and based on the internal forces. The anchors and the wood screws are designed on the basis of the calculated bearing forces, the applicable national technical approvals (AbZ) (Z-9.1-...) or the corresponding European Technical Assessment (ETA-...). The design of the connections to the reinforced concrete structure will in future be governed by DIN EN 1992-4, which is currently being drafted. Reference should be made to DIN EN 1995-1-1 for the wood screw connection of the steel angle to the timber panel construction element. In the event of a complex folding plate analysis being required in the design of

Fire load scenario Fire load load scenario scenario Fire

the connection profile, Li [19] suggests the following relationship is used as the value for the concrete substrate c: cConcrete = 15 ∙ fc, cube The above represents a coherent means by which the connections can be designed. The connections are then chosen to match the calculated design loads. Every element should have between two and four connection points to minimise the installation work. Usually anchor bolts with a diameter of 10 to 12 mm are used, while 6 to 8 mm diameter wood screws normally attach the timber facade elements by means of the vertical studs. The floor or slab construction can then be appropriately completed to conceal the connections once the facade is in place.

Notes: [1] DIN EN 1995-1-1:2010-12, Eurocode 5: Design of timber structures – Part 1-1: General – Common rules and rules for buildings. Section 9.2.4 (Wall diaphragms) [2] Holzabsatzfonds (pub.): Holzrahmenbau. Informationsdienst Holz. holzbau handbuch, Series 1, Part 1, Section 7. Bonn 2009, p. 12 [3]  As note 1, section 9.2.4 [4] Mette, Elmar: Transportieren und Montieren. ­Holzbau – die quadriga 03/2014, p. 23 –27 [5] Official Journal of the European Union. Council Directive 96/53/EC establishing for certain road vehicles circulating within the Community the maximum authorised dimensions in national and international traffic and the maximum authorised weights in international traffic. 1996 [6] German Road Traffic Licensing Regulations ­(StVZO) in the version in force from 11.03.2015. Last amended by: Verordnung zur Änderung der Fahrpersonalverordnung, der Straßenverkehrs-­ Zulassungs-Ordnung und der Verordnung über den grenzüberschreitenden Güterkraftverkehr und den Kabotageverkehr dated 9 March 2015. Federal Gazette. I No. 9 p. 243, issued in Bonn on 9 March 2015. German Federal Ministry of Transport and Digital Infrastructure. § 32 (1), line 31 [7] ibid., § 32 (1), line 26 [8] Komzet Bau Bühl Kompetenzzentrum der Bau wirtschaft (pub.): Transport von Bauteilen. ­Osnabrück 2011

Load-bearing Structure and External Wall

  [9] Information source: Kreisverwaltungsreferat ­Munich [10] German Road Traffic Regulations (StVO) in the version in force from 26.09.2015. Last amended by: F ­ ünfzigste Verordnung zur Änderung straßen­verkehrsrechtlicher Vorschriften dated 15 September 2015. Federal Gazette. I p. 1573 art. 2, issued in Bonn on 25 September 2015. § 46 (1), section 5 23 [11]  As note 9 [12] As note 6, § 32 (2) StVZO and § 22 (2) StVO [13] Verkehrsblatt Document No. B. 5756: Kennzeich­ nung von Ingenieurbauwerken mit beschränkter Durchfahrtshöhe über Straßen. Dortmund 2000, clause 1.2 [14] DIN 18 202:2013-04: Tolerances in building ­construction – Buildings p. 5 [15] DIN EN 1992-1-1:2011-01, Eurocode 2: Design of concrete structures – Part 1-1: General rules and rules for buildings. Section 7.4 [16] Stein, René; Schneider, Patricia; Kleinhenz, ­Miriam; Dotzler, Christina; Volz, Christof; Hessinger, Joachim: Fassadenelemente für ­Hybridbauweisen – Vorgefertigte, integrale Fassadenelemente in Holzbauweise zur Anwendung im Neubau hybrider Stahlbetonhochbau­werke. Technical University Munich, Chair of Timber Structures & Building Construction, Chair of ­Energy Efficient & Sustainable Design & Building and Chair of Concrete & Masonry Structures. Munich 2016 [17] DAfStb: Hilfsmittel zur Schnittgrößenermittlung und zu besonderen Detailnachweisen bei Stahlbetontragwerken. Based on DIN EN 1992, in: DAfStb-Heft, issue 631. Issued May 2019, issue 631. Berlin 2019 [18] Merk, Michael: Untersuchungsbericht Belastungsversuche zur Bestimmung der Verschiebesteifigkeiten an Wand-Decken Verbindungs­ elementen. Prüfstelle Holzbau, MPA Bau. Technical University Munich. Munich 2015 [19] Li, Longfei: Recommendation for concrete substrate. E-mail from Dr. Li, Anchor Profi GmbH Stuttgart. Stuttgart 2015

Design situation

Normal load scenario (quasi-permanent)

Fire load scenario (accidental)

Partial safety factors

γg = 1.35 γq = 1.50

γg = 1.00 γq = 1.00 ψ1 = 0.00

Compatibility load factor

sf = 0.5

sf = 1.0

Undercut anchor

Expansion anchor

Resin-bonded anchor with chemical grout

Concrete screw anchor

e.g. Hilti HDA-T, Fischer Zykon FZA

e.g. Hilti HST3, Fischer FAZ II

e.g. Fischer Highbond e.g. Hilti HUS-H 10, Würth W-BS Anchor Rod FHB II -A L Inject, Würth WIT-VM & W-WIZ

Immediate ­load-bearing ­capability

No disruptive effect from anchor installation

Immediate load­ bearing capability

Full-surface material bonding

Full-surface material bonding

Anchor forces ­concentrated at ­expansion sleeve

Anchor forces concentrated at expansion sleeve

Can be loaded only ­after injection grout has cured

High cost

Disruptive effect from anchor ­installation

Disruptive effect High cost from anchor ­installation

Cast-in anchor channel

e.g. Hilti HAC-30, HTA-Halfen channels

Advantages 21 S  ection detail a Section detail of a self-supporting timber ­panel construction element (for vapour barrier arrangement, see “Floor Slab Joint, Self-­ supporting External Wall Elements; With ­Services Cavity”, p. 53) b Possible static system for the design of the connection 22 Static system for the facade for the normal and the fire load scenarios 23 Overview of the partial safety factors and load factors for the design of the facade element ­connections 24 Advantages and disadvantages of currently available connections in reinforced concrete 24 ­construction

Immediate load­ bearing capability

No drilling necessary

Disadvantages Cannot be adjusted in position later

31

Building Physics

Christoph Kurzer Stefan Winter Joachim Hessinger

1

Thermal Insulation Aspects of energy efficiency have led to developments in building construction in recent decades that have placed increased importance on thermal insulation. Existing and new buildings require a high-quality thermal building envelope capable of sustainably limiting heat loss in winter and heat gain in summer. The level of thermal insulation determines a building’s environmental footprint, especially during the use phase. In Germany, the thermal insulation standard for buildings greatly depends on statutory guidelines and regulations, which are subject to ­continual amendment. The legal framework described below is based on the situtation in 2019. The German government laid the foundations for the country’s present standard of thermal insulation with its introduction of the Energy Saving Ordinance (EnEV) in 2002. A steady flow of amendments led to the current requirements, which have applied since the beginning of 2016. When it comes into force, the Buildings Energy Act (GEG) is intended to supersede the EnEV for the statutory regulation of thermal insulation. In Germany, the minimum requirements for thermal insulation of a building are governed by the DIN 4108 series of standards. Hybrid construction combines the building physics advantages of a reinforced concrete structure with those of a timber frame panel construction element facade. Timber frame construction elements combine a thin cross section with a relatively high thermal resistance. The high thermal storage capacity of the reinforced concrete structure stabilises the indoor climate. Winter Thermal Insulation

The climatic conditions in Germany mean that winter thermal insulation is one of the basic requirements in the design and

construction of buildings. The many different functions of the thermal building envelope include the maintenance of a hygienic indoor climate, the long-term preservation of the building fabric and minimising thermal losses. Particularly by limiting heat transfer through the external building components, the required heat energy can be sustainably reduced, so that the energy demand falls and the building becomes more environmentally compatible in the use phase. The different temperatures inside and outside the building lead to heat transport through the thermal building envelope. From a construction point of view, heat transfer paths cannot be completely elim­inated, which is why only a reduction of the heat flux can be achieved. Heat is transported by thermal conduction, convection and radiation. In the case of opaque building components, e.g. the timber frame construction elements of the facade, thermal conduction is responsible for the major part of the heat flux. Convection needs to be taken into account at the transitions between building component surfaces and the outdoor or indoor air. Thermal radiation has most effect as energy entering the building through transparent components. The emission of heat energy from a building into the environment is termed heat loss in the building industry. The required

level of limitation of these heat losses is set out in the provisions of the EnEV. The EnEV applies limits only to primary energy demand and transmission heat loss. When assessing transmission heat losses, the entire thermal building envelope is evaluated; the EnEV does not impose any binding requirements on the thermal transmittance of individual building components. From the notional design of a reference building, guide values (Fig. 1) for the thermal transmittance of individual building components can be indirectly derived according to their type. Since January 2016, a reduction factor of 0.75 has applied to the primary energy demand of the reference building, i.e. a flat-rate reduction of thermal transmittances [1]. The thermal transmittance U for a component of the thermal building envelope is usually calculated using the simplified calculation method given in DIN EN ISO 6946. As the core element of the ­timber frame construction element facade is usually made up of a number of different layers, upper and lower limit values of the thermal resistance R must be determined [2]. The different thermal conductivities of the materials in the inhomogeneous building component layer means heat flows are concentrated into the materials with higher thermal conductivities, in this case the wooden ribs of the timber frame construction elements (Fig. 2). This

Type of building component

Up to 31.12.2015

From 01.01.2016 1)

External walls, Ceiling slabs against outdoor air

U = 0.28 W/m K

U = 0.21 W/m2K

Floor slab, External walls against earth, walls and ceilings adjacent to unheated rooms

U = 0.35 W/m2K

U = 0.26 W/m2K

Roof, highest ceiling slab

U = 0.20 W/m2K

U = 0.15 W/m2K

Thermal bridge correction factor

ΔUWB = 0.05 W/m2K

ΔUWB = 0.0375 W/m2K

1) 

1

 hermal transmittances of the reference building T for use as guide values

2

 aking into account the 0.75 reduction factor applied since January 2016 to the highest permissible annual T primary energy demand

33

Untitled-1.THM ( 18%)

Therm Version 7.6.1.0 (1 of 1)

2 a

b

thermodynamic process must therefore be properly taken into account when considering the thermal transmittance U of the timber frame panel. Despite the inhomogeneous layered structure of timber frame panels, this type of external wall component has a consider­ able advantage over the alternative conventional concrete construction, in that it achieves the same thermal insulation standard but is much slimmer. A comparison of examples of different constructions for an external wall, each with a thermal transmittance of 0.150 W/(m2K), illustrates the difference between the individual wall

thicknesses (Fig. 3). A timber panel construction element using an external thermal insulation composite system (ETICS) has an external wall thickness of 320 mm. A conventional reinforced concrete wall with an ETICS would require a total thickness of approximately 490 mm. Timber frame construction can therefore provide 0.17 m2 additional usable floor area per linear metre of facade for the same building volume. Hybrid construction is particularly suitable for modern and sustainable buildings, which must achieve a much better level of insulation because of the minimum

3 a

b

4 a

b

34

insulation standard required by the German Energy Saving Ordinance (EnEV) (for standards see Fig. 10, p. 12). When assessing the transmission heat losses for the heat energy demand, the heat loss due to heat flowing across thermal bridges must be taken into account, in addition to the heat lost though large, flat building components. The higher the insulation standard of the building, the greater the importance of heat lost across thermal bridges. Thermal bridges are weak points in the thermal building envelope caused by e.g. reductions in insulation thickness, geometric features or penetrations of the insulation layer by materials with a higher thermal conductivity. By allowing the addition of a correction factor, the EnEV provides a very conservative estimate of the effects of a building’s thermal bridges. In the case of buildings with a high insulation standard (e.g. low-­ energy buildings), this flat-rate approach to calculating the effects of thermal bridges becomes unworkable because the value greatly exceeds the losses for such a building in reality. DIN 4108 gives design and construction examples of connections commonly used in practice for non-hybrid structures [3]. The connection arrangements between the ­timber frame construction facade elements and the reinforced concrete ­structure are not covered by any standard (Fig. 4) and therefore additional calculations are required for them in hybrid ­construction. The detailed analysis of thermal bridges is done in accordance with the provisions of EN ISO 10 211, EN ISO 13 370 and EN ISO 13 789. The following general rules of construction can be used as a guide in considering the effects of unavoidable thermal bridges in hybrid construction: • Increasing the thickness of thermal insulation layers in roofs and floor slabs already designed to a high energy

3

4

 imber panel construction element T a Representation of the position of the limiting ­values for the thermal transmittances. Upper limiting value in the area of the wooden ribs, lower limiting value in the area of the thermal ­insulation b Schematic temperature distribution in the building component Comparison of two facade constructions with a U-value of 0.150 W/m2K a Reinforced concrete external wall with ETICS b  Timber panel construction element Example connections a Inserted timber panel construction element b  Suspended timber panel construction element

standard does not improve the situation with thermal bridges at the connections. • The designer should depart as little as possible from the generally accepted rules of construction. In other words, suitable measures should be adopted such that the connecting components have the same level of thermal insulation as the heat-transmitting enclosing surface. • ETICS provide a continuous layer of insulation over the connection areas and thus diminish the effect of thermal bridges. • To minimise the effect of thermal bridging and the risk of moisture condensing inside building components, less than 20 % of the total insulation thickness should be on the indoor side of the vapour control and airtightness ­layers [4]. Fascia connection: • A fascia has a favourable effect on thermal insulation. The insulation of the external wall should reach at least up to the top edge of the roof insulation. Floor slab connection: • In the case of suspended timber frame construction elements, the thickness of the reinforced concrete floor slab has no significant influence on thermal bridging (Fig. 5). • Positioning a service cavity in suspended curtain wall timber frame construction elements increases the effect of thermal bridges at the connections. Therefore, the thickness of the insulation fitted between the frame members of the panel should not be reduced to less than the thickness of the insulation in the service cavity. • In the construction of rear-ventilated facades, the insulation thickness of the service cavity should not make up more than one fifth of the total insu-

5

6

 onnection point of suspended timber panel C ­construction elements a Influence of slab thickness on a thermal bridge (length-related thermal transmittance) b Connection used in tests to determine the ­influence of slab thickness (most unfavourable arrangement) Connection point for inserted timber panel ­construction element a Influence of corbel length on a thermal bridge (length-related thermal transmittance) b Connection used in tests to determine the ­influence of the degree of insertion (most ­unfavourable arrangement)

lation thickness of the timber frame construction element. • In the case of self-supporting timber frame construction elements in front of the main load-bearing structure, in which vertical load transfer takes place at the bottom of the panel, butt joints between elements in the plane of the slab should be avoided if possible. • In contrast to the floor slab thickness, the degree of insertion of the facade has a significant influence on thermal bridge formation. From a structural engineer’s point of view, the minimum possible degree of insertion should be used to minimise the risk of buckling of the external wall (Fig. 6). Base connection: • Insulation of the floor slab inside the building is particularly advantageous in avoiding the formation of ­thermal bridges. During construction, attention must be paid to providing moisture protection, sound insulation and the amount of thermal insulation permitted by the manufacturer. • The vertical perimeter insulation must always extend to the bottom of the floor slab or the horizontal perimeter insulation.

0.039 0.037 0.035 0.033 0.031 0.029 0.027 0.025 0.023 200

210

220

230

240

250

260

270

280

300 290

Floor slab thickness [mm]

5 a

h

b ψe-value [W/mK]

2

ψe-value [W/mK]

Building Physics

0.039 0.037 0.035 0.033 0.031 0.029 0.027 0.025 0.023 25

30

35

40

45

50

Degree of insertion [%]

6 a

Summer Thermal Insulation

The aim of summer thermal insulation, the d = 300 mm minimum requirements for which are set out in DIN 4108-2, is to prevent the interior of the building from overheating. The users’ feeling of thermal comfort depends x d = 135 mm on the indoor air temperature and the surface temperature of the surrounding building components. People engaging in normal activities can expect to show reduced performance when the room air temperature exceeds 25 °C. Whether or not the surface temperature is comfortable to users depends partly on the actual room air temperature [5].

d = 300 mm

x

d = 135 mm

b

35

7a

b

Hybrid construction makes a positive contribution to summer thermal insulation in several ways. The relatively low thermal transmittance of the timber frame construction elements due to the required winter thermal insulation effectively at­ tenuates the amplitude of the temperature difference cycles between the internal and external sides of the building component. In spite of large day-night fluctu­ ations of surface temperature on the outside of the building of almost 20 kelvin, the corresponding fluctuation of surface temperatures inside the building is less than 1 kelvin. The reinforced concrete structure, which acts as a large thermal store, has a positive effect on the summer thermal insulation and the analyses take appropriate account of this effect in accordance with the relevant standards.

humidity and temperatures near and on the surface of the building component. DIN 4108-2 gives appropriate minimum insulation requirements for thermally ef­ fective building components. In the case of hybrid construction, the high standard of insulation of the panels excludes the possibility of mould formation. The temperatures on the inner surfaces of the components are normally only a few tenths of a degree below room temperature, which raises the relative humidity of the nearby air by only an insignificant amount compared to the average indoor relative humidity. In the area of thermal bridges caused by connections to the reinforced concrete structure, the designer should take into account the information given in the section on “Thermal insulation” (p. 33ff.). Condensation

Moisture Protection It is essential that moisture is continually conducted out of buildings or prevented from occurring in the first place. Building users risk harm and the building construction considerable damage from the unplanned occurrence and uncontrolled effects of moisture. Possible negative consequences include damage to the building fabric, a less effective thermal building envelope or a reduced quality of indoor climate, which may even cause users to become ill (e.g. mould, sick building syndrome). Protection against moisture should therefore be given careful consideration during design and construction.

The formation of condensation within the external building components must be avoided or at least limited as much as possible. In general, the stored quantity of water arising from condensation in the component during the dew period (December to February) should be limited to 1.0 kg/m2 or 0.5 kg/m2 on and in vapour barrier layers. With timber frame construction, it is also important to limit the change of moisture content of each material, such as wood (+5 % by mass) and wood-based materials (+3 % by mass). The possible quantity of condensate can be estimated using the Glaser method in accordance with DIN 4108-3. It should also be checked whether the condensation formed can evaporate over the evaporation period (June to August).

thermal or moisture leaks can occur. Leaks due to lack of airtightness give rise to slow-moving currents of air (convection) through the construction. On its way to the open air, the warm building air cools in the building component to the extent that water condenses there. The moisture quantities entering building components through this convection effect are difficult to determine in practice. They are taken into account in hygrothermic calculations, e.g. in accordance with EN 15 026, as an annual add­itional quantity of moisture in the component of e.g. 250 g/m2a. Advice for the design of the timber frame construction element facade: • For vapour diffusion tightness, the maxim is: as open as possible, as tight as necessary! More vapour-permeable layers on the interior side allow the panel construction walls to dry out in summer and make the construction more robust against moisture (paper instead of plastic bags) • The vapour-retarding airtightness layer should run on the interior side of the core element behind the service cavity. • The external cladding of the core element should be as vapour-permeable as possible. • There should be an external windtight layer to act as a second practically airtight layer to prevent convection flows (see “Air and Windtightness”, p. 37ff.) • The component layers on the interior side should be much more diffusion-­ retardant (by about five to ten times) than the outer component layers. • Mineral plasters are recommended for use with ETICS

Mould Formation

Preventing moisture from occurring on the indoor surfaces of the components of the thermal building envelope is the main way of protecting against mould formation. The crucial factors here are the relative 36

Airtightness

In addition to the external walls having the correct vapour diffusion properties, particular attention must to be paid to the airtightness of the building. Otherwise

Externally, the facade must withstand the effects of driving rain. Requirements for the materials used to provide this weather protection are specified according to the exposure groups in DIN 4108-3. In

Building Physics

Airtightness Airtightness layer layer

Airtightness Airtightness layer layer

7

8

 einforced concrete column R a Bottom of a reinforced concrete column before installation of the external wall b Front view of the reinforced concrete column ­including a layer of insulation, on the right: the cross section of a self-supporting timber panel construction element set forward of the concrete structure Arrangement of the airtightness layer a For self-supporting timber panel construction ­elements b For inserted timber panel construction elements

hybrid construction, rear-ventilated timber facades or ETICS with water-repellent plasters can be designed to meet even the highest of these requirements. A second water-directing layer should always be provided on the outside to improve robustness against moisture.

Air and Windtightness In order for the building envelope to maintain the effectiveness of its building-­ physical properties, it must be constructed to be air and windtight (see “Moisture Protection”, p. 36f.). Adequate airtightness prevents air flowing through building components as a result of air pressure differences between inside and outside the building (wind currents, ventilation systems). The windtightness of the outer surface of the building is intended in particular to prevent air from flowing through the thermal insulation due to wind exposure. It is also a second means of ensuring airtightness. Defects in the air and windtightness layers of a building often lead to adverse effects on the protection of its construction against moisture, heat, sound and fire [6]. The design and installation of the air and windtightness layers should be in accordance with the requirements and recommendations of DIN 4108-7, which contains additional prac­tical examples for overlaps, connections and penetrations for various parts of the building construction. The special challenge in hybrid construction is the proper design and construction of connections and the surrounding areas, taking into account the different tolerances for reinforced concrete and timber construction. In particular, the prefabrication of the timber frame construction elements requires careful detailing (see “External Wall Joints”, p. 49ff.). However, the high quality of the panels brings

8 a

the significant advantage of far fewer leakages than are typically found in other types of buildings. Designers should observe the following guidance for the building envelope to ensure adequate air and windtightness: • Airtightness must be achieved by at least one layer. Combining several inadequate airtightness layers does not guarantee adequate airtightness [7]. • The airtightness layers of the building envelope must continuously enclose the building interior, i.e. they must have no breaks or interruptions. The various parts of each airtightness layer must form a completely bonded whole [8]. • The cladding on the interior side of the core elements is particularly suitable for ensuring airtightness in timber frame construction elements. The external windtight layer provides the secondary level of protection against leaks. • As is the case with vapour diffusion, the maxim “inside tighter than outside” applies. With airtightness, however, it should always also be “as tight as possible”. • In the case of self-supporting timber frame construction elements set in front of the load-bearing structure, the airtightness layer of the building envelope, e.g. OSB boards attached by adhesive, continues across the end of the floor slab (Fig. 8 a). In addition, the airtightness between the building’s usage units is guaranteed by extra glued-on components on both sides (smoke exclusion, sound and odour protection). • Air or windtight layers usually perform two functions. Depending on their ­pos­ition in the component, they can also be the second water-directing layer, a breathable or vapour diffusion-­ tight layer. • In the case of inserted timber panel construction elements, the airtightness layer with film must be run around the

b

intruding reinforced concrete components (Fig. 8 b). • The plaster acts as the windtightness layer where an ETICS is used. • For rear-ventilated facades, the outside cladding of the core element must provide windtightness or be supplemented by a suitable breathable film.

Fire Protection Since the effectiveness of a building’s fire protection is proven only in the extra­ ordinary situation of a fire, it may be years before undetected poor-quality construction results in catastrophic consequences. Focused and diligent design and construction is therefore essential. The objective of an effective fire protection concept is to prevent a fire from occurring, to contain fire and smoke in the event of a fire, to allow self-rescue, the evacuation of others and effective fire extinguishing [9]. In addition to structural stability, fire protection is one of the important requirements in eliminating acute risks to life and limb. Legal Requirements

Laws and regulations have much to say on the fire protection for buildings. In Germany, the legislation governing the design of fire protection for buildings is continually changing. The legal framework described below is based on the ­situation in 2019. Furthermore, the approach of the German design rules for fire protection is profoundly different to that in other European countries, though the standards they aim to achieve are comparable. The German Model Building Code (MBO) sets out all the general requirements for building construction and their principal aim of achieving the protection goals [10]. In contrast to other protection goals, those for fire protection 37

 9 E  lement butt joints between external and internal walls (drywall and reinforced concrete wall) ­including membranes glued in place ready for screeds 10 Criteria for classification into building classes 11 Fire protection requirements for different building components 12 Fire protection requirements applying to building facades 13 Attachment of a timber panel construction ­element

9

Range where hybrid construction is particularly efficient Building class

11)

2

Total footprint m2

≤ 400 m2

≤ 400 m2

3

4

Floor area of a usage unit

≤ 400 m2

Number of usage units

≤2

≤2

FFL of highest floor with habitable room

≤7m

≤7m

1)  2) 

5 2)

≤7m

≤7m

≤ 22 m 3)

Plus: free-standing buildings used for agriculture or forestry purposes Including underground buildings Buildings in which the height of the uppermost floor FFL is more than 22 m are classified as building class 5, but also as a high-rise building. The German Model High-Rise Building Guidelines (MHHR) set higher ­requirements than those for building class 5 in the building regulations, so the limit for consideration in this project is the high-rise limit of 22 m.

3) 

10

Building component

Building class

Construction type in hybrid construction

3

4

5

Load-bearing walls, columns

fh

hf

fb

Reinforced concrete

Load-bearing walls, columns in basement

fb

fb

fb

Reinforced concrete

Non-load-bearing external walls

–

nb or fh

nb or fh

Separating walls

fh

hf

fb

Reinforced concrete

Ceiling slabs

fh

hf

fb

Reinforced concrete

Ceiling slab in basement

fb

fb

fb

Reinforced concrete

hf + M

fb + M

Reinforced concrete

Firewall / firewall replacement wall

hf

1)

Timber panel construction

Building enclosure firewall in F 30 / F 90 construction fh – fire retardant, hf – highly fire retardant, fb – fire resistant, M – mechanical impact, nb – non-flammable 11 ‡ = Timber with no departures from the MBO can be used 1) 

12

Construction element

Building class 1 to 3

Building class 4 and 5

Surfaces (External wall cladding)

Normally flammable

Flame-retardant

Insulation and subconstruction

Normally flammable

Flame-retardant or normally flammable, ­providing fire propagation is limited for an ­adequate period of time

Rear-ventilated external wall cladding

None

Precautions to limit fire propagation

38

are directly included in the MBO by detailed requirements for the fire behaviour of construction materials and the fire resistance rating of building components. The MBO gives “standard fire protection concepts” for the various building classes (descriptive minimum requirements). Because building laws are determined at state level in Germany, there are 16 sets of State Building Regulations (LBO), each differing slightly from the other. The Model Building Code (MBO) is approved by the German Building Ministers’ Conference. This is a set of non-binding recommendations and serves as the basis for the various state building regulations. In general, the applicable state building regulations, including any supplementary rules, must be observed in the design and construction of buildings. The legal requirements for fire protection depend on the building class. MBO § 2 defines five building classes. Since the beginning of 2019, all state building reg­u­ lations have classified buildings into building classes. The criteria include the total floor area or the area of a usage unit, the number of usage units and the height of the uppermost finished floor surface of a habitable room above the average terrain surface (Fig. 10). The fire protection requirements for building components and e.g. escape routes in a building depend on the building class. The higher the building class, the more stringent the requirements need to be to reflect the increasing hazard potential. These requirements relate in particular to components that ensure structural adequacy, room enclosure or combine the two functions. The fire-resistance rating of the building component is classified into one of the following three categories: “fire-retardant” (30 minutes), “highly fire-­ retardant” (60 minutes) and “fire-­resistant” (90 minutes). The official classification

Building Physics

13

also considers the way the material behaves in fire. For example, com­busti­ ble materials are not permitted in “fire-­ resistant” components. Fig. 11 shows the requirements for building classes 3 – 5. The combination of construction methods adopted in hybrid construction is optimised for usability, while remaining compliant with the legal fire protection requirements of the MBO. The reinforced concrete structure can achieve the required ­fire-­resistance rating in the various ­building classes by relatively simple ­construction measures (concrete cover). Reinforced concrete construction also meets the ­material class requirement (non-com­bustible) for the loadbearing structure in a class 5 building. Lower fire protection requirements apply to non-structural ­external walls. They must – if made from com­bustible materials ­(German classification B1) such as wood – be classified as “fire-retardant” (30 minutes) in the higher building classes. Timber frame construction elements are inherently capable of achieving this level of fire resistance. Therefore hybrid construction can be used without departure from the fire protection requirements up to the height limit (≤ 22 m). The MBO calls for additional requirements relating to the reaction to fire of the materials used at the facades (see “Construction of the Timber Panel Construction Elements”, p. 8f.) [11]. The building class is also important in determining the requirements here (Fig. 12). The official protection goal is to prevent fire from propagating across the facade. Verification of Timber Panel Construction Walls

In principle, the designer can fulfil the fire protection requirements in a number of different ways in order to verify the suitability for use of the non-load-bearing timber frame construction elements. In addition to normative rules for designing

components to achieve the required fire-resistance rating, manufacturers may have their own verification documentation. Important resources on which verification of applicability can be based in building practice include: • EN 1995-1-2 Annex E, taking into account the German National Annex EN 1995-1-2/NA (Design) • Tables from DIN 4102-4, in future based on Amendment A1 • National test certificate for a construction product (abP) (manufacturer dependent) • National technical approval (abZ) for materials (manufacturer dependent) • General construction technique permit (aBG) (manufacturer dependent) Simplified calculation methods or data from tables can be used in the design for all the methods shown. The calculation methods permit a specific assessment of the actual construction. With data from tables, on the other hand, the constructions are specified and no significant deviations allowed. For the actual certification of the room-­ enclosing function of the timber panel construction element facade, it is recommended that only the core element is taken into account (see “Construction of the Timber Panel Construction Elements”, p. 8f.) – all the layers in the component do not have to be considered. Therefore, the layers on the outside in front of the core element can be ignored, without detriment to the fire resistance period of the assessed core element. Using the same approach, the architect or building services engineer can also use the service cavity on the inside (Figs. 2 and Fig. 3, p. 8) for the cable runs and pipework without fire protection constraints. The facade could then also be adapted independently of the room-enclosing function to satisfy the fire protection

requirements regarding fire propagation alone in the building regulations. The room-enclosing function of the timber panel construction element facade in hybrid construction can then be verified with the calculation method in accordance with Annex E of EN 1995-1-2, taking into account the German provisions of DIN EN 1995-1-2/NA. The load-bearing capacity is not calculated and is not required for the facade elements. Here the room-­ enclosing function describes the performance properties smoke exclusion (integrity) E and limiting the temperature of the unexposed, “cold” side of the component (insulation) I. The calculation method can be used only for fully enclosed timber frame construction elements with a maximum of two layers of wood-based material cladding in accordance with EN 13 986 and gypsum-­based plasterboard type A, H or F in accordance with EN 520. Products made from mineral wool (stone and glass wool) can be evaluated as thermal insulation. The maximum permitted value for the fire-resistance rating of 60 minutes is ­adequate for the certification of the timber frame construction element facade, because only “fire-retardant” (30 minutes) components are required for building class 4 up to the high-rise building limit (classification REI 30 or F 30-B; in REI, R = Résistance, load-bearing capacity (preserves mechanical characteristics); E = Étanchéité, integrity (blocks fire and smoke); I = Isolation, insulation (reduces heat transfer)). Fig. 15 (p. 40) shows the calculation method for two ­simple core elements in timber frame construction. Results show that the core element can generally fulfil the required fire-resistance rating of 30 minutes. The outer facade or the inner service cavity does not have to be considered in this example. The facade must also meet the fire protection requirements. From building class 4 upwards, “flame-retardant” materials 39

14 E  xternal wall with timber cladding: steel sheets were installed as fire barriers at each floor to meet fire protection requirements. 15 Examples of calculated values for the core ­element of the timber panel construction element ­facade 16 Possible timber facade constructions for timber facades with fire aprons 17 Fire protection requirements in the connection ­area in accordance with DIN EN 13 501-2 18 Schematic representation of the track of the 300 °C isotherm (for the purpose of investigation using a simple ceiling construction) a Timber panel construction elements with glass wool (15 kg/m3) b Timber panel construction elements with stone wool (26 kg/m3)

14

Core element with 200 mm glass wool insulation

Layer

Thickness Material

tins [min]

1

15

OSB (EN 13 986)

13.9

2

200

Glass wool (EN 13 162)

18

3

16

MDF (EN 13 986)

15.5 47.3

Core element with 200 mm stone wool insulation

1

15

OSB (EN 13 986)

13.9

2

200

Stone wool (EN 13 162)

40.0

3

16

MDF (EN 13 986)

86.2 > 60

The calculation uses a joint coefficient kj = 1.0, which means that the joints are backed with laths or wooden 15 ribs in the construction as necessary.

Cladding type

Material / component

Example

Direction

Depth of Minimum projection [mm] the rear ventilation ≥ 200 ≥ 100 ≥ 50 ≥ 20 cavity [mm]

Large, flat woodbased ­material

•  Bulk density ≥ 330 kg/m3 •  Fully enclosed •  Board thickness ≥ 18 mm •  Edge length ≥ 200 mm •  Board area ≥ 0.20 m2

• Solid wood boards • Crosslaminated timber • Veneer ­plywood • OSB • Chipboard

Hori­ zontal / vertical

≤ 100

‡

‡

‡

‡

Hori­ • Tongue and Inter­locking • Stress relief grooves: groove boards zontal / boards residual thickness ≥ 10 mm Profiled cover vertical groove spacing ≥ 30 mm strip boards •  Cladding thickness ≥ 18 mm Tongue and • Board width: groove pith-free ≤ 160 mm semi-rift or rift ≤ 250 mm

≤ 100

‡

‡

‡

‡

Hori­ zontal

≤ 100

‡

‡

‡

vertical

≤ 100

‡

‡

Hori­ zontal

≤ 100

‡

‡

vertical

≤ 100

‡

• Rebated • Stress relief grooves: Forceboards transferring residual thickness ≥ 10 mm T-profile groove spacing ≥ 30 mm boards boards •  Cladding thickness ≥ 18 mm •  Board width heartwood-free Open boards

16

• Board thickness ≥ 18 mm • Board cross-section area ≥ 1,000 mm2 • Cover strip thickness ≥ 10 mm •  Board width heartwood-free

• Open boards • Board and moulding • Board on board • Weather­ boarding • Board and ­batten

‡ =  Fire-safe facade constructions by equivalent fulfilment of the legally stipulated “B1” protection goal

40

are required in the facade area to ad­ equately limit the propagation of fire over the facade. When evaluating an external thermal insulated composite system (ETICS), the manufacturer’s certificate must declare the reaction to fire of the system in the installed state. The construction mea­ sures to achieve the required reaction to fire of the whole system often vary with the insulation thickness of the ETICS. Wood is considered in DIN 4102-4 as “normally flammable”, which is why timber facades require further construction mea­ sures in order to achieve an equivalent reaction to fire to that stipulated in the relevant state building regulations. The risk in the use of timber in the surfaces of the external walls including their sub-­ constructions is that timber can contribute to the propagation of the fire over the facade before the fire service arrives and extinguishes the fire. The critical propagation paths of the fire are in the rear ventilation cavity and on the facade surface. Horizontal fire stops must be provided at each floor in the case of timber facades to achieve the officially required protection goals. Depending on the facade type, these fire stops must project far enough out from the front edge of the facade surface (Fig. 16) and there must be a non-combustible layer capable of providing effective fire protection fastened to the back of the facade. Suitable construction measures must be taken and the timber facade system carefully detailed to adequately limit fire propagation over the facade, so that the officially required protection goals are achieved and a solution technically equivalent to a “flame-retardant” facade is provided [12]. Verification of Reinforced Concrete Components

In hybrid construction, the structural elem­ents are generally made of reinforced concrete. For building classes 4

Building Physics

Compliance Compliance with with with performance performance Compliance performance criteria criteria (R)EI(R)EI (R)EI on fire-remote on fire-remote fire-remote side side side criteria on Ceiling Ceiling REI 90 REI 90 90 Ceiling REI

Airtight Airtight Airtight glued glued glued membrane membrane membrane

Airtight Airtight Airtight glued glued glued membrane membrane membrane

90 min. 90 90 min. min. 60 min 60 60 min min min 30 min 30 30 min

17

Transfer Transfer of performance of performance performance criteria criteria Transfer of criteria to connection to connection connection areaarea area to wall wall EI 30 Non-load-bearing Non-load-bearing external external wall EI 30 30 Non-load-bearing external EI 18 a

and 5 in particular, the use of reinforced concrete makes it easier to satisfy the fire protection requirements for the load­ bearing structure. Reinforced concrete is non-combustible and can therefore be used for “fire-resistant” components. The fire-resistance rating of reinforced concrete components depends above all on the concrete cover to the steel reinforcement and can be taken into account by the structural engineer when calculating the load capacity of the structure in the event of a fire. Important standards for the evaluation of the fire-resistance rating of reinforced concrete components include: • EN 1992-1-2 (Eurocode 2), taking into account the provisions of the German National Annex DIN EN 1992-1-2/NA •  DIN 4102-4 Verification of the fire-resistance rating of reinforced concrete components is performed using data from tables, or by using simplified or general calculation methods. Hybrid construction has no effect on the normative verification of the reinforced concrete components, because the complexity of the fire protection design remains the same. Fire Paths in the Connection Area

The non-load-bearing timber frame construction external wall elements and the load-bearing reinforced concrete structure in hybrid construction have different requirements for fire resistance (see “Legal Requirements”, p. 37ff.). The connection areas between the components must therefore be carefully considered in the design (Fig. 17). Particularly in the case of building class 5, a fire protection conflict occurs in the connection of the “fire-­retardant” (30 minutes) external wall to the “fire-resistant” (90 minutes) components of the loads-bearing structure. In addition to the horizontal connections of the facade elements to the floor slabs,

this is also the case at the vertical con1.6 1.6 1.6 14.014.0 14.0 1.5the 1.5 1.5separating walls of usage nections to units, stairwell walls and firewalls or “firewall replacement walls” (internal fire walls with reduced requirements) (see “Vertical Joints”, p. 64ff.). § 28 MBO requires the connection of the facade elements to the reinforced concrete components to be designed such that the transmission of the fire within the external wall component via the floor slab is limited for an adequate period. In terms of the regulations, the connection must have a fire resistance that meets the requirements applying to the external wall. In the case of these connections, the secondary fire paths must be obstructed by non-combustible joint insulation (mineral wool with a melting point ≥ 1,000 °C in accordance with DIN 4102-17 and a bulk density ≥ 30 kg/m2). The joints between the floor slabs and the facade elements must be glued so as to be airtight. The airtight glued membrane on the side facing the fire inside the building provides a seal against smoke propagation in the event of fire. Therefore a glued membrane must be attached at the bottom and top surfaces of the floor slab. A better understanding of the connections can be obtained from Fig. 18, which shows the temperature profiles of a 200-mm thick slab designed in accordance with DIN 1992-1-2 with a fire load on one side. The 300 °C isotherms for the reinforced concrete slab are shown for fire resistance periods of 30, 60 and 90 minutes. The isotherms are transferred onto the timber frame construction elements and used to estimate the calculated boundary for the expected combustion. The tracks of the isotherms show the anticipated temperature distribution in the area of the connections. After 90 minutes of exposure to fire, the effects of the fire

90 min. 90 90 min. min. 60 min. 60 60 min. min. min. 30 min. 30 30 min.

b

on the connection point are of no conse1.6 1.6 1.6 14.014.0 14.0 1.5 1.5 1.5 quence and therefore the required fire resistance of the concrete load-bearing component is maintained in both situations [13]. The airtight glued membrane is essential in this arrangement because the connection must be smoketight in order to prevent fire from breaking through.

Sound Insulation The following pages describe the requirements for sound insulation in buildings in Germany and look specifically at how they apply and how compliance is verified for hybrid construction. Analysis and discussion on sound insulation in buildings have been made with respect to the German Building Code, German Standard DIN 4109 and construction practice in Germany. Proof of performance for sound insulation in building projects in Europe outside Germany is subject to different building codes, and thus varying levels of sound insulation requirements including partially different acoustic parameters apply. However, sound insulation of single building components as presented e.g. in Fig. 22 below can be used as input data for design of acoustic insulation as per international standard EN ISO 12 354-1. Sound Insulation Requirements

With increasingly dense development and high outdoor noise loads in cities, the sound insulation of buildings in Germany is an important factor in creating a healthy environment in which to live and work. Minimum Sound Insulation in Accordance with DIN 4109 In Germany, DIN 4109-1 is the main standard containing the official requirements for insulating building interiors against sound, including the noise from building services systems and outdoor 41

Building type / component

Requirements in DIN 4109

Sound insulation according to VDI 4100 sound insulation classes I

II

III

Airborne sound separating wall

R'w ≥ 53 dB

DnT, w ≥ 56 dB

DnT, w ≥ 59 dB

DnT, w ≥ 64 dB

Airborne sound separating floor

R'w ≥ 54 dB

DnT, w ≥ 56 dB

DnT, w ≥ 59 dB

DnT, w ≥ 64 dB

Impact sound separating floor

L'n, w ≤ 50 dB (≤ 53 dB)

L'nT, w ≤ 51 dB

L'nT, w ≤ 44 dB

L'nT, w ≤ 37 dB

19 Special requirements for impact sound insulation for timber construction and renovation shown in brackets

noise. The requirements apply irre­ spective of the type of construction and are intended to be the minimum required level of sound insulation, which must be met even without further contractual obligations. Sound insulation inside the building is quantified by the parameters R'w (weighted apparent sound reduction index) for airborne sound insulation and L'n, w (weighted normalised impact sound pressure level) for impact sound insulation. Sound insulation is provided to attenuate all transmission of sound from room to room, i.e. the directly transmitted airborne and impact sound plus the sound transmitted through other paths such as the adjacent walls and floors (flanking sound transmission). Required values from DIN 4109-1 are shown in excerpt form in Fig. 19. The requirements for sound insulation against outdoor noise are specified in terms of the critical outdoor noise level La for the total weighted apparent sound reduction index R'w, tot depending on the type of room use determined using the equation R'w, tot = La – K type, where Ktype ranges between 25 dB (hospital wards), 30 dB (habitable rooms in residential buildings) and 35 dB (offices). An additional correction term KAL allows

Ff

for the geometrical boundary conditions of the room, i.e. the ratio of room ­volume to external surface area. The total weighted apparent sound reduction index R'w, tot covers the sound ­transmission through all components of the building envelope, i.e. through the external wall, windows, French windows etc. Enhanced Sound Insulation in Residential Buildings in Accordance with VDI 4100 The general and blanket application of sound insulation measures in resi­ dential buildings to achieve only the ­minimum requirements of DIN 4109 has often been criticised in recent years and has since led to some landmark ­decisions by the German Federal Court of Justice (BGH) [14]. Therefore in civil law contracts an agreement for ­target v­ alues for sound insulation is ­common. These target values represent an increased level of sound insulation compared to the minimum requirements given in DIN 4109. The guidance values for enhanced sound insulation in residential building interiors include e.g. the provisions of VDI 4100, which defines three insulation levels (sound insulation classes (SSt)) (Fig. 19). In designing the enhanced sound insulation called for in

Df

ng room

Receiving room

Transmitting room Dd Fd

20

42

Ff

19 R  equirements and target values for the airborne and impact sound insulation of building ­interior components, with typical values for ­residential separating walls and floors in apartment blocks in accordance with DIN 4109 and enhanced sound insulation in accordance with VDI 4100:2012-10 20 Sound insulation of a separating wall, representation of sound transmission paths, direct Dd and via flanking components Df, Fd and Ff for airborne sound excitation. 21 Description of external wall construction and ­connection to the separating building component

VDI 4100, it should be noted that the design values in the current version of this guideline differ from earlier documents in that they are based on reverberation time-related parameters DnT, w (standardised sound level difference) and L'nT, w (standardised impact sound level). This makes the design more complicated because the room’s geometrical boundary conditions (volume, separating component surface area, direction of sound transmission) must be taken into account. Verification Process

The verification of compliance of sound insulation in accordance with DIN 4109 is done by calculation. The calculation rules for this are set out in DIN 4109 Part 2. The input data for the calculation is either taken from the component ­catalogue (DIN 4109 Parts 31 to 36) or can be determined from laboratory tests. The sound insulation designer can also use information in the declaration of ­performance provided in accordance with national approvals, a CE ­marking on the basis of a European ­harmonised product standard or a ­European Assessment Document (EAD, formerly European Technical Approval ETA) as initial data for the calculations. In the context of t­imber external walls in hybrid construction, the airborne sound insulation inside the building and the sound insulation against outside noise largely determine the quality of the sound insulation performance, which is why the following pages will focus on these two aspects. Sound Insulation between Rooms, Taking into Account Flanking Sound Transmission To verify compliance of the airborne sound insulation, the sound insulation designer must calculate the total sound power transmitted over the various avail­ able paths (direct sound penetration

Building Physics

21

through the separating building component and flanking sound transmission, Fig. 20). The geometric boundary con­ ditions such as surface area and edge lengths of the building components involved must be taken into account in accordance with DIN 4109-2. The relevant sound transmission paths are: • Sound transmitted directly through separating building components, ­characterised by the weighted sound reduction index Rw, in the case of heavy building components (e.g. concrete or masonry), using the area-related mass. The higher the area-related mass, the greater the sound insulation. • Flanking sound through external building components, characterised by the weighted normalised flanking sound level difference Dn, f, w, depending on the construction of the external wall, the connection to the separating building component and the quality of the installation joint (see e.g. “Flanking and Airborne Sound Insulation in Timber Walls in Hybrid Construction”, P. 43). The ­situation of flanking sound transmitted through external building components can be improved, for example, by decoupling the external wall element (as well as through installing separate elements for each room). • Flanking sound transmitted through internal building components characterised by the weighted normalised flanking sound level difference Dn, f, w or by the flanking sound reduction indices RFd, w and RDf, w (if heavy building components are involved at this location), depending on the construction of the internal building components, area-related masses, connections to the separating building component and quality of construction of the installation joint (this will not be further discussed, as it is not relevant here).

Construction

Description

Core element

15 mm wood-based board DHF (vapour-permeable, moisture-resistant wood fibreboard) 60/140 mm timber studs with mineral fibre insulation 15 mm wood-based board P7 (suitable to support loads in moist areas)

Wall lining

Can be directly mounted or free-standing with 1 or 2 layers of 12.5 mm gypsum plasterboard

Butt joints

External wall, self-supporting or inserted

Construction of the joint with the separating building component

Fully filled with mineral fibre insulation, sealed optionally on both sides with multifunction tape or flexible sealant

The required value for the flanking sound insulation in the form of Dn, f, w cannot be directly derived from the required value for sound insulation, i.e. the weighted apparent sound reduction index R'w. However, a rule given in DIN 4109-2 [15] allows the designer to estimate a target value for Dn, f, w, which is 7 dB higher than the required sound reduction index R'w. Thus, for a requirement value of R'w = 54 dB, the target value is Dn, f, w = 61 dB. Sound Insulation against External Noise The total weighted apparent sound reduction index R'w must be determined for the verification calculation of the sound insulation against outside noise. This is done by adding up the sound energy flows through the individual components of the building envelope (e.g. external wall, windows, ventilation equipment etc.). DIN 4109-2 provides further details. The calculations can also take into account the installation situation of windows and its effect on sound transmission. This requires a joint sound reduction index for the installation situation, which is then used in a conditional equation for the resulting sound reduction index. DIN 4109-2 [16] provides information to assess whether an installation situation is critical or non-critical in terms of sound transmission. An installation situation assessed as non-critical for sound transmission does not have to take account of sound transmission through installation joints in the construction. Situations assessed as critical for sound transmission are those in which the window is located in the plane of the thermal insulation layer (e.g. in an ETICS). Safety Concept DIN 4109 incorporates a safety concept to allow for uncertainties in the use of measured values and data from tables.

First the sound insulation parameters R'w and L'n, w are calculated using values determined in the laboratory, the values from the building component catalogue, an approval, EAD or the CE marking (see “Verification Process”, p. 42). Uncertainties are then taken into account by the use of a safety factor uprog, which is subtracted from the airborne sound reduction index resulting from the calculation for a specific situation within a building (building authority regulation with a coverage factor k = 1). Consideration of the safety factor uprog in the airborne sound insulation for a given situation within a building: R'w – uprog ≥ req. R'w in [dB] for sound insulation in building interiors with uprog = 2 dB (usual value) R'w, ges – uprog ≥ req. R'w + KAL in [dB] for sound insulation against outdoor noise with uprog = 2 dB Flanking and Airborne Sound Insulation in Timber Walls in Hybrid Construction

As part of a study by the Technical University of Munich, the flanking sound insulation of external walls in timber panel construction in the horizontal and vertical directions was investigated for use in hybrid construction [17]. Fig. 21 shows an overview of the tested specimens and the investigated variants. Flanking Sound Insulation of the Basic Construction Depending on the Type of Construction Fig. 24 (p. 45) shows typical values of the flanking sound insulation Dn, f, w for a selection of constructions. The flanking sound insulation values recorded in the study are in principle comparable with those from the building component catalogue in DIN 4109-33, although there are individual differences due to the ­different construction details (e.g. cladding mater­ials, the quality of the instal­ 43

Better sound insulation thanks to connection plate on both sides and sealing towards ceiling and facade

Sound path

22

lation joints, element coupling etc.). Since the wall constructions used in actual buildings are likely to differ from the tested constructions, the following section “Airborne sound insulation as ­protection against external noise” (p. 46) provides information on the transferability of sound insulation values and general recommendations for improved sound insulation of such constructions. Projects with examples of typical constructions and connection details can be found in the section on “External wall joints” (p. 49ff.). Using the above rule for the estimation of Dn, f, w with the minimum requirements in accordance with DIN 4109 gives target values of Dn, f, w = 60 dB for the horizontal flanking sound insulation and Dn, f, w = 61 dB for the vertical flanking sound insulation. These values can be achieved in the external timber construction walls depicted above, although sometimes requiring additional measures.

Standard flanking level difference Dn,f [dB]

Flanking Sound Transmission – Acoustically Effective Improvement Measures Achieving adequate flanking sound insulation in a timber facade depends mainly on the construction details. The follow-

4,000

ing guidelines and advice can be used in the design of the various connection points. Quality of the installation joints The sound transmission from room to room takes place not only through the separating floor or wall but also through the installation joints between the external facade and the separating component. Filling the joint completely with fibre insulation is not enough to eliminate this sound transmission. The joint must also be covered and sealed on both sides. A research project by the Technical University of Munich [18] studied only the effect produced by applying a building connection joint membrane to both sides. Where higher requirements apply for sound insulation, and depending on the joint width and depth, it may be necessary to provide additional metal sheet covers (e.g. thin steel sheets covering the joint between the facade and the separating building component) or bulkheads using e.g. plasterboard. Internal fitting out components (e.g. floor construction, suspended ceiling etc.) can be used to cover the joints on the room side to further improve flanking sound insulation (Fig. 22). A quantitative statement on the improve-

ment potential of these various measures in general in this context cannot be made and compliance must be verified on a case-to-case basis. Installation situations for external walls Whether the facade is constructed as a self-supporting or an inserted external wall considerably influences flanking sound insulation. For vertical flanking sound insulation in particular, a self-supporting external wall transmits much more flanking sound than an inserted wall (Fig. 23). In the case of a self-supporting external wall, additional measures such as room-side wall linings may be necessary to meet the requirements for minimum sound insulation. For horizontal flanking sound insulation, the difference between the two installation methods is not so pronounced, assuming that the joint to the separating wall is located at the unit joint (continuous on the complete height of the element) of the external wall panels. A separating wall connection in the middle of the external wall element was not investigated as part of the study, which means separate testing and verification may be necessary in specific cases.

80 70

Basic construction: Core element, installation joint filled with mineral wool and self-adhesive sealing tape on both sides, no over-bridging by ETICS, no wall lining

60 50

Influence of installation position: Green line: Inserted core element Dn, f, w = 64 dB

40 30 20

cy [Hz] 23

Blue line: Self-supporting core element Dn, f, w = 51 dB

63

125

250

500

1,000

2,000

4,000 Frequency [Hz]

44

Building Physics

Summary of transmission direction and connection situation

Effect of wall linings In the case of self-supporting external walls in particular, the use of room-side wall linings is required to block sound from entering the external wall construction. Free-standing wall linings (e.g. gypsum plasterboard on a separate metal stud sub-construction) offer more advantages than wall linings that are fastened directly to the external wall – even if the latter form of construction would be suf­ ficient to meet the minimum sound insu­ lation requirements in accordance with DIN 4109. Figs. 24 and 25 (p. 46) give some examples of measured results from self-supporting external walls. Coupling of the wall elements Measurements are normally performed without external thermal insulation on the timber walls. In practice, the external walls are covered with thermal insulation, which provides an additional coupling of the wall element and therefore reduces flanking sound insulation. In some cases, the coupling of the wall elements was tested with externally applied vapour-­ permeable wood fibreboard sheathing panels. Fig. 24 shows typical measured results from self-supporting external walls (with wall lining):

 Horizontal and vertical sections

Results of flanking sound insulation measurement Dn, f, w (C; Ctr) 1)

Horizontal flanking sound insulation for a self-supporting external wall with directly mounted wall lining (1 layer 12.5 mm gypsum plasterboard)

71 (-3; -9) dB

Horizontal flanking sound insulation for a self-supporting external wall with directly mounted wall lining (1 layer 12.5 mm gypsum plasterboard), external walls coupled via ­vapour-permeable wood fibreboard (comparable with coupling using ­ETICS)

66 (-2; -8) dB 2)

Horizontal flanking sound insulation for an inserted external wall without a wall lining, external walls coupled via vapour-permeable wood fibreboard (comparable with coupling u ­ sing ­ETICS)

60 (-3; -7) dB 2)

Vertical section of a separating floor: Vertical flanking sound insulation for a self-supporting external wall with ­directly mounted wall lining (2 layers 12.5 mm gypsum plasterboard) (Sound protection improves in the case of a self-supporting wall lining; the values are shown in brackets)

66 (-2; -7) dB (69 (-1; -6) dB)

Vertical section of a separating floor: Vertical flanking sound insulation of an inserted external wall without wall lining

64 (-1; -5) dB

22 Improvement of flanking sound insulation by ­additional building measures or constructions by others on site (connection sheets with sealant, floor constructions, suspended ceilings). An ­example of improvement measures is shown for an inserted external wall (without wall lining). 23 Sound insulation graph for vertical flanking sound insulation comparing inserted and self-supporting external walls: The sound insulation graph shows the flanking sound insulation as a function of the All the connections shown above assume that the installation joint is completely filled with mineral fibre and frequency over the range 50 Hz (low) up to 5 kHz sealed on both sides with polyethylene self-adhesive tape. (high). For the inserted core element, the flanking Wall linings, when present, had a continuous peripheral seal against the building components. sound insulation achieved was much better than 1) C and Ctr are spectrum adaptation terms. They are evaluated as additional information in accordance with test that for the self-supporting external wall over a standards and brought into consideration to evaluate the suitability of building components in specific noise frequency range of 100 Hz to 5 kHz. situations as far as sound insulation is concerned (e.g. noise from household activities, traffic noise). They are 24 Horizontal and vertical flanking sound insulation not mandatory for verifications in accordance with DIN 4109 in Germany. of external wall constructions for hybrid construc2) In some variants, the external walls in the neighbouring rooms are coupled by a vapour-permeable wood tion buildings (values from tests in the project ­report by Technical University of Munich, 2016) 24 ­fibreboard.

45

• External wall in neighbouring rooms without coupling Dn, f, w = 71 dB (see line 1 in Fig. 24, p. 45) • External wall in neighbouring rooms coupled using vapour-permeable wood fibreboard sheathing panels Dn, f, w = 66 dB (see line 2 in Fig. 24, p 45) In the case of a self-supporting facade, in which the load transfer takes place through the elements into the level below, the influence on the vertical flanking sound insulation is considered small. In other cases, in which high sound insulation is required, it is recommended that the separation of the facade elements is extended beyond the insulation layer. Modification of the wall construction The tests for flanking sound insulation are performed on a simple timber stud wall with room-side cladding made from 15-mm chipboard. In terms of sound ­insulation, this represents a rather unfavour­able arrangement, which allows the results to be used for other wall constructions incorporating e.g. additional room-side cladding or services cavities. The installation of window frames into external wall elements has a positive or neutral effect on flanking sound insulation.

25 a

46

The following advice may be useful when designing sound insulation for walls and windows (practical verification on a case-by-case basis depends on the project requirements and the type of construction): • Timber panel construction walls using ETICS and a services cavity / wall lining

achieve sound insulation of Rw = approx. 41 dB to 71 dB, where the best sound insulation values are achieved by walls with free-standing wall linings. • Timber stud walls with rear-ventilated facades and a services cavity / wall ­lining achieve sound insulation of Rw = approx. 46 dB to 71 dB, where the best sound insulation values are achieved with free-standing wall linings. • Single windows typically achieve sound insulation values between Rw = 30 dB and 47 dB. • With coupled windows, the sound ­insulation values are usually between Rw = 35 dB and 52 dB. • The resulting sound insulation for the whole external wall depends on the window and external wall construction, on the proportion of window area, the quality of the installation joints (seals) and any additional equipment such as ventilation devices and solar protection systems. It must be ­verified whether the installation joint between the window and the external wall results in any significant additional sound transmission (see “Verification Process”, p. 42f.). This can be calculated by the sound insulation design engineer.

b

25 F  lanking sound insulation of a self-supporting ­external wall with wall lining a Self-supporting external wall with directly mounted wall lining (2≈ 12.5 mm gypsum ­plasterboard) Dn, f, w = 66 dB b Self-supporting external wall with free-­ standing wall lining to improve sound insulation (2≈ 12.5 mm gypsum plasterboard) Dn, f, w = 69 dB For comparison: measurement at a self-­ supporting external wall without wall lining Dn, f, w = 51 dB 26 installation of non-load-bearing timber panel construction external walls with fascia (see example project “Ecoleben Penzberg”, p. 82ff.)

Airborne sound insulation as protection against external noise Investigation into whether sound insu­ lation protects against outdoor noise must be done on a case-by-case basis. Building component parameters for the walls can be found in the building com­ ponent catalogue in DIN 4109 [19]. If ­windows are integrated into the external facade, their sound insulation must be verified using the rules in the product standard EN 14 351-1. Verification can ­be based either on data from tables or measured values. In the case of verifi­ cation using data from tables, the sound insulation of the window is largely determined by the sound insulation of the glazing. Design engineers can estimate the sound insulation of windows from Table 1 in DIN 4109-35. Information about the sound insulation of roller shutter boxes is contained in DIN 4109-35 [20].

Building Physics

Notes: [1] In accordance with EnEV, Annex 1, tab. 1, line 1.0, dated 24.10.2015 [2]  In accordance with DIN EN ISO 6946:2018-03 [3] In accordance with DIN 4108 Supplement 2:2006-03 [4] In Kaufmann, Fritz et al.: Das Passivhaus – ­Energie-Effizientes-Bauen. Informationsdienst Holz. holzbau handbuch, Series 1, Part 3, Section 10. pub. Holzabsatzfonds and DGfH. ­Munich  /Bonn 2002 [5] In Frank, Walther: Raumklima und Thermische ­Behaglichkeit. Berichte aus der Bauforschung, vol. 104. Berlin 1975 [6] Ref. Holzabsatzfonds; DGfH (pub.): Funktions­ schichten und Anschlüsse für den Holzhausbau. Informationsdienst Holz. holzbau handbuch, ­Series 1, Part 1, Section 8. Bonn /Munich 2004 [7] In Peper, Søren; Feist, Wolfgang; Sariri, Vahid: Luftdichte Projektierung von Passivhäusern. Eine Planungshilfe. Passivhaus Institut. Darmstadt 2003 [8] ibid. [9] Ref. §14, German Model Building Code (MBO)

[10] German Model Building Code (MBO). Second Part. Version dated Nov. 2002, last modified by the resolution of the German Building Ministers’ Conference on 13.05.2016 [11] Ref. § 28, German Model Building Code (MBO). Version dated Nov. 2002, last modified by the resolution of the German Building Ministers’ Conference on 13.05.2016 [12]  In Hafner, Annette; Schäfer, Sabrina; Krause, ­Karina; Rauch, Michael; Merk, Michael; Werther, Norman; Opitsch, Wolf: Methodenentwicklung zur Beschreibung von Zielwerten zum Primär­energie­ aufwand und CO2-Äquivalent von Baukonstruktionen zur Verknüpfung mit Grundstücks­vergaben und Qualitätssicherung bis zur Ent­wurfsplanung. Final report of the Chair of ­Resource Efficient Building at Ruhr University Bochum. Research Project of the German Federal Environmental Foundation, AZ 31943. Bochum 2017 [13] In Technical University of Munich. Lehrstuhl für Holzbau und Baukonstruktion, Lehrstuhl für ener­gieeffizientes und nachhaltiges Planen und Bauen, Lehrstuhl für Massivbau (pub.): Fassa­ denelemente für Hybridbauweisen – Vorgefer-

tigte, integrale Fassadenelemente in Holzbauweise zur Anwendung im Neubau hybrider Stahl­ betonhochbauwerke. Final report. Munich 2016 [14] For an overview see e.g.: Hettler, Steffen: Technische Regelwerke zum Schallschutz – Rechtliche Einordnung, pub. by DIN Deutsches Institut für Normung e. V. Berlin 2018 [15]  Ref. DIN 4109-2:2018-01, Section 4.2.4 [16]  Ref. DIN 4109-2:2018-01, Tab. 5 [17]  As note 13 [18] ibid. [19] Ref. DIN 4109-33:2016-07. Tab. 6 and 7 include characteristic data for verification calculations. The following can also be used for estimating the sound insulation of external walls during the design phase: Holtz, Fritz et al.: Schallschutz – Wände und Dächer. Informationsdienst Holz. holzbau handbuch, Series 3, Part 3, Section 4, pub. by Holzabsatzfonds and DGfH. Bonn 2004 Scholl, Werner; Bietz, Heinrich: Integration des Holz- und Skelettbaus in die neue DIN 4109. ­Final report of the PTB on the research project, funded by DIBt and PTB. Brunswick 2004 [20] Ref. 4109-35:2016-07, Tab. 6

26

47

External Wall Joints – Horizontal Joints

External Wall Joints

Christina Meier-Dotzler Christoph Kurzer Patricia Schneider-Marin Christof Volz 1

2

Horizontal Joints – General Requirements and Guidance Horizontal joints are connections of the timber panel construction element to horizontal reinforced concrete building components such as roof, intermediate floor / ceiling and ground floor slabs. They create a force-transmitting connection and conduct the vertical loads arising from the self-weight of the external wall elements and the horizontally acting wind loads through the reinforced concrete floor or floor slabs into the foundations. The principles of these connections are explained in the section “Principles” (p. 7ff.), and information about the structural analysis can be found in the section “Load-bearing Structure” (p. 19ff.). The installation of the timber panel construction elements and their connections normally proceeds floor by floor. So that work on site can react flexibly to the manufacturing tolerances of the re­inforced concrete components, the connections should be designed to use steel angles, wood screws, concrete screws or anchor bolts (see “Connections”, p. 28ff.). The distance between connections is often the same as the spacing of the timber studs. The joints must meet the requirements not only for moisture and fire protection but also for thermal and sound insulation. If they are not designed correctly, their protective properties might cancel each other out. For example, joints designed for sound decoupling may, as the result of poor design, fail to provide the intended protection against fire (see “Building Physics”, p. 33ff.). The floor-by-floor ­construction sequence also includes balconies and access balconies. In these ­circumstances, the timber panel construction wall elements are erected first, and then the balconies or access balconies

(e.g. as reinforced concrete components or steel constructions), and then both are connected to the reinforced concrete load-bearing structure (see p. 56f.). The new block of 35 subsidised housing units in Freising (p. 86ff.) provides a good example of a barrier-free access balcony in reinforced concrete. The designer overcomes this detailing challenge by creating a discrete recess for a load-­ bearing thermal insulation element and staggering the top rail downwards within the frame (Fig. 3, p. 50 and connection detail “Access balcony”, p. 56f.). The connection details shown on the ­following pages were developed during a research project in cooperation with building contractors. All details have been developed with respect to German building regulations and construction practice. Details and definitions may be ­different in other countries, which all have their own regulations. Nevertheless, the details and accompanying structural-­physical terms can be used for comparison purposes. They comprise slab connections for self-supporting and for inserted external walls, two connections at the bottom of the building – one with the position of the bottom rail outside the splash water zone and one at ground level – and for a flat roof slab joint. The following general rules apply: • Wall linings, e.g. to accommodate a services cavity, are normally constructed on site. • Where increased sound insulation requirements apply, a free-standing wall lining with steel profiles is recommended (Fig. 1 b). However, in the case of min­imum sound protection requirements, the wall lining can be installed directly onto the core element, an arrangement which will provide an adequate sound insulation performance (Fig. 1 a).

 urtain wall facade (vertical section) C a Direct attachment to the core element by ­horizontal timber laths b Free-standing installation at a distance from the core element using metal C profiles Beam types: a  Solid structural timber b  I beam c  C beam d  Z beam

The details show timber panel construction elements manufactured from structural timber beams and columns. The U-value of the component was assessed as 0.15 W/m2K. The selected insulation standard exceeds the requirements of the German Energy Saving Ordinance (Energieeinsparverordnung – EnEV) (see “Construction of the Load-bearing Structure”, p. 7f.), which also means the construction is suitable for the low energy standard. The effects of any thermal bridges created were not calculated, because they depend on materials used, in particular the insulation material. There

1 a

2

b

a

b

c

d

49

3

 chematic diagram of the connection of the S ­load-bearing thermal insulation element with ­staggered top rail

Supplementary insulation

Angle joint sufficiently offset from connection of load-bearing thermal insulation element

Subsequent backfilling with concrete

Framing offset of lower wall element

Load-bearing thermal insulation element

3

50

Precast columns and precast ceiling slab connected by bolts

are, however, recommendations for improving thermal bridging situations. Timber panel construction elements normally consist of solid structural timber (German: Konstruktionsvollholz – KVH), but they can also be made using fabricated timber joists (Fig. 2). These are light timber beams with flanges fabricated from structural timber, glued lamin­ ated timber (GLT) or laminated veneer lumber (LVL) and webs from oriented strand board (OSB) or hardboard. These types of joists should be used where thermal insulation requirements are high and therefore thermal bridges must be avoided. These joists are designed and used in accordance with their specific approvals (e.g. European Technical Assessment, ETA). There are no universally applicable sizes for the connections shown in the details. In practice, these connections are project-­specific and may differ from those shown. All relevant building components and connection elements must be structurally checked in each case. The connection elements (e.g. steel angles) should not be visible when the building is complete. Wood screws are normally threaded for their full lengths and screwed into predrilled holes if necessary, so that the required edge clearances and fastener to fastener spacings can be reduced. In the case of the self-supporting facade, set in front of the load-bearing structure, the fully threaded wood screws need to be designed only to carry horizontal tensile forces. The vertical loads (selfweight of the wall elements) are transferred via the wall elements into the ­foundation. This means the horizontal joints between them must be capable of transferring these forces. To avoid ­vertical loads being transferred from the reinforced concrete slabs (thus loading the screws in shear), the screwed

External Wall Joints – Horizontal Joints

connections are designed to have elongated holes and spacer sleeves. This gives the joint some freedom to deform, which will be required as a result of e.g. floor slab deflections. The section on “Connections” (p. 28ff.) explains some specific aspects of their design. Concrete screw anchors or anchor bolts should be positioned within the edge ­reinforcement to ensure an adequate ­distribution of the force in the anchor. The edge clearances and fastener spacings required for the full load-carrying capacity of screw anchors or anchor bolts must be checked in each case. In general, only wood screws or concrete screw anchors or anchor bolts with valid approvals for use in construction (national or European technical approval – AbZ or ETA respectively) may be used. The standard solution is often equal or unequal steel angle sections in accordance with EN 10 056-1 [1]. Customised welded angle sections may also be used. The following standard constructional details and information about connections are accompanied by building physics parameters and other data about Thermal Insulation: • U-values and information about re­ ducing thermal bridges Sound Insulation (according to the German technical standards): • Weighted sound reduction index and spectrum adaptation terms Rw (C, Ctr), • Weighted normalised impact sound pressure level and spectrum adaptation term Ln, w (CI) and • Weighted normalised flanking level ­difference and spectrum adaptation terms Dn, f, w (C, Ctr) • The spectrum adaptation terms C, Ctr and CI are not required for verification in accordance with DIN 4109.

Fire Protection (according to the German building code): •  Guidance on fire protection In Germany, the required fire protection depends on the defined building class (see Fig. 10, p. 38). Depending on the building class, the requirements may apply to the non-load-bearing external walls and the fire behaviour of their components. No special fire protection requirements apply up to and including building class 3. For building class 4 and above, the external wall must have a fire-resistance rating of 30 minutes (EI 30), and it is advisable for this to be satisfied by the core element alone, so that there is more flexibility in the design of the other layers. In addition, the materials in the facades for building class 4 and 5 must limit the spread of fire and be classified as “flame-retardant” (A1, A2 and B1 in accordance with the German classification system). This in turn reduces the choice of construction materials e.g. for thermal insulation. Other information for the construction of the facade is contained in the section on “Fire Protection” (p. 37ff.). Ventilated facades (air gap interrupted at each floor) are preferred to rear-­ ventilated facades (air gap continuous) because they do not create a chimney effect in the event of fire (fire propagation caused by additional air introduced through the ventilation openings). More detailed information on compliance with fire protection requirements on national or international level, the design of building components, their parts and the avoidance of secondary fire paths can be found in the section on “Fire Protection”, (p. 37ff.). Facades and external walls must also comply with moisture protection and ­airtightness requirements.

• In Germany, the requirements for achieving adequate airtightness are contained in DIN 4108-7 [2]. This standard forms the basis for air and smoketight glued-­ ­on membranes in the following connection details. • The relevant German standards about wood preservation are DIN 68 800-1 [3] and DIN 68 800-2 [4]. • Protection of walls against driving rain is covered in DIN 4108-3, Section 6 [5]. • Joints and connections must also be designed to keep out driving rain. This can be achieved using constructional measures or by joint sealing materials in accordance with the German DIN 18 540 [6], sealing tapes or foils. Ventilated external wall cladding provides durable, effective weather protection if it has official approval for such use. This also applies to thermal insulation composite systems and render carrier boards. Further information about standards can be found in the Appendix (p. 94).

Notes: [1] EN 10 056-1:2017-06 Structural steel equal and unequal leg angles – Part 1: Dimensions; German version, English version EN 10 056-1:­2017-01 [2] DIN 4108-7:2011-01 Thermal insulation and en­ ergy economy in buildings – Part 7: Air tightness of buildings – Requirements, recommendations and examples for planning and performance (in German) [3] DIN 68 800-1:2019-06 Wood preservation – Part 1: General (in German) [4] DIN 68 800-2:2012-02 Wood preservation – Part 2: Preventive constructional measures in buildings (in German) [5] DIN 4108-3:2018-10 Thermal protection and ­energy economy in buildings – Part 3: Protection against moisture subject to climate conditions – Requirements, calculation methods and directions for planning and construction (in German) [6] DIN 18 540:2014-09 Sealing of exterior wall joints in building using joint sealants (in German)

51

Floor Slab Joint, Self-supporting ­External Wall Elements; With Services Cavity

Vertical load is transferred by contact pressure between the two wall elements. The steel angle connects the wall elements to the reinforced concrete slab and supports them in the horizontal plane. The maximum deformation of the reinforced concrete slab must be ≤ 10 mm. The wall elements are protected from deformation by the vertical elongated holes and the spacer sleeves used with the connecting wood screws. The floor construction should be free of services.

11.

8.

4.

1.

5.

2.

10.

3.

6.

9.

6.

7.

8.

Installation and Joint Construction

1. F  asten the steel angle to the reinforced concrete floor slab 2. F  ix the insulation strip in accordance with EN 13 162 (melting point > 1,000 °C) onto the front edge of the reinforced concrete slab shortly before installing the external wall 3. Install the external wall element on the lower floor including the render ­carrier board 52

4. Install the external wall element on the upper floor including the render carrier board 5. Inspect the butt joint on site for ­flushness and rectify if and where ­necessary 6. E  nsure air and smoketightness (top and bottom), e.g. with self-­ adhesive tape 7. Apply ceiling plaster or fill voids at the

  reinforced concrete slab /wall corners   8. Construct the services cavity (here using horizontal laths)   9. Seal continuously the gypsum plasterboard type DF (GKF) joints at the wall, ceiling and floor to improve sound insulation in accordance with EN 15 651-1 10. Apply render 11. Install floor construction

External Wall Joints – Horizontal Joints

Vertical section  Scale  1:10 1

2

3 4 5 6 7 8 9

 imber panel construction element: T Thermal insulation composite system (with approval for construction use) consisting of 8 mm plaster 60 mm fibre insulation board (WLS 045) 16 mm MDF board (medium density fibreboard, windtight layer) vapour-permeable 160 mm solid structural timber (KVH) (a = 62.5 cm stud spacing), thermal insulation filling (WLS 040) 15 mm OSB board (airtight layer) 60 mm services cavity with structural timber (KVH) subconstruction (a = 62.5 cm stud spacing), thermal insulation ­filling (WLS 040) 2≈ 12.5 mm gypsum plasterboard type DF (GKF) Floor construction: 12 mm floor covering 70 mm cement screed 0.2 mm PE film separating layer 30 mm impact sound insulation (WLS 045) 40 mm thermal insulation (WLS 040) 260 mm reinforced concrete slab with 30 mm ­insulation strips at the front edge 10 mm plaster Force-transmitting joint between top and bottom rails 2≈ 2 wood screws (e.g. full thread screw (VGS) 8.0 ≈ 140 mm) with spacer sleeves and elongated holes Concrete anchor bolt /screws with plain washer (e.g. M 12) Steel angle (e.g. L150/200/12 mm, S 235) Glued membrane (air and smoketightness) Flexible joint seal Flush butt joint of the fibre insulation boards

1

4

5

6

7

2

3 9

4

8 7

Sound Insulation

Thermal Insulation and Moisture Protection

Fire Protection

Dn, f, w (C; Ctr) = 65 (-2; -7) dB

Uwall element = 0.15 W/m2K

Wall element: RW (C; Ctr) = 45 (-1; -6) dB (applies to the depicted wall construction in accordance with DIN 4109-33, Table 6, line 6)

Ensuring the laths in the services cavity are positioned at a distance from the reinforced concrete slab re­ duces thermal bridging. The height of the bottom and top rails should be kept to the minimum required for structural purposes to ­reduce potential thermal bridging.

So that the wall construction complies with the re­ quirements for building classes 4 and 5, the core elem­ent must have a fire-resistance rating of 30 minutes (EI 30). In Germany, verification of ­usability must be provided for the core element construction (e.g. DIN 4102-2). In addition, the ­materials in the facades for building class 4 and 5 must limit the spread of fire, therefore the facade system must comply with the German reaction to fire classification of “flame-­retardant” (A1, A2 or B1 in accordance with the ­German classification system). These arrangements e ­ ffectively suppress fire spread across the facade. The design must also consider secondary fire paths in the area of the joint.

Reinforced concrete slab: R  W = 67 dB Ln, w = 37 dB Sound insulation values of the floor slab do not take into account flanking sound transmission. They apply to the depicted construction, 260 mm thick, floating screed with m' ≥ 140 kg/m2 and impact sound insulation board with s' ≤ 20 MN/m3 (in accordance with DIN 4109-2, DIN 4109-32 and DIN 4109-34).

53

Floor Slab Joint, Inserted External Wall Elements; No Services Cavity

Vertical load is transferred by contact pressure, with the mortar bed able to compensate for any slight differences in level. Steel angles connect the timber panel construction elements to the re­ inforced concrete slab and support them in the horizontal plane. Both steel angles are installed, correctly positioned and aligned before the timber panel elements are installed. To allow a flush joint on the room side and to conceal the steel angle, the OSB board on the lower timber panel element must be cut to shape to fit the steel angle in the connection area. The floor construction should be free of services.

13. 7.

5.

12.

1.

12.

6. 4.

9.

10.

8.

3.

2.

11.

Installation and Joint Construction 

1. F  asten the lower steel angle to the ­reinforced concrete slab 2. Install the external wall element for the storey below 3. F  ix the insulation strip or loose insulation in accordance with EN 13 162 (melting point > 1,000 °C) between the top rail and the reinforced concrete slab 4. Achieve airtightness by continuing the film, keeping its correct place in the order of layers, from the lower timber panel element into the floor above 54

5. F  asten the upper steel angle to the reinforced concrete slab 6. Install a levelling layer (cement mortar and spacer pieces) 7. Install the external wall element of the floor above 8. F  ix the insulation strip in accordance with EN 13 162 (melting point > 1,000 °C) onto the front edge of the reinforced concrete slab 9. C  onnect the upper and lower wall ­elements by extending an MDF board (medium density fibreboard)

  or facade membrane 10. Install the facade system (here: ­ventilated or rear-ventilated facade) 11. Apply ceiling plaster or fill voids at the reinforced concrete slab /wall ­corners 12. Plaster over the steel angle: seal continuously the gypsum plasterboard type DF (GKF) joints at the wall, ceiling and floor to improve sound insulation in accordance with EN 15 651-1 13. Install floor construction

External Wall Joints – Horizontal Joints

Vertical section  Scale  1:10 1

2

3 4 5 6 7 8 9

 imber panel construction element: T 24 mm timber external wall cladding (e.g. larch) in accordance with fire protection requirements 30/50 mm timber lath subconstruction (e.g. spruce), staggered, 16 mm rear-ventilated MDF board (windtight ­layer), vapour-permeable 300 mm solid structural timber (KVH) (a = 62.5 cm stud spacing), 2≈ 150 mm thermal insulation filling (WLS 040) 15 mm OSB board (airtight layer) 12.5 mm gypsum plasterboard type DF (GKF) Floor construction: 12 mm floor covering 70 mm cement screed 0.2 mm PE film separating layer 30 mm impact sound insulation (WLS 045) 40 mm thermal insulation (WLS 040) 260 mm reinforced concrete slab with ≥ 50 mm insulation strips (WLS 040) in front of the floor slab edge and above the top rail 10 mm plaster Levelling layer (force-transmitting bearing ­layer under bottom rail) with spacer pieces and cement mortar Vapour barrier (sd ≥ 1 m) and glued-on ­membrane (air and smoketightness) MDF board (terminates the windtight layer in ­accordance with fire protection requirements, e.g. attached by screws) Concrete anchor bolt /screw with plain washer (e.g. M 12) Steel angle (lower e.g. L150/150/12 mm, S 235; upper e.g. L150/100/12 mm, S 235) 2≈ wood screws (e.g. full thread screw (VGS) 8.0 ≈ 140 mm) with spacer sleeves and elongated holes Flexible joint seal

1

9 6 7

2

8

3

4

5 9 8

6

7

Sound Insulation

Thermal Insulation and Moisture Protection

Fire Protection

Improved sound insulation can be achieved by not joining wall elements with an MDF board but by ­allowing this connection to be flexible in bending (e.g. using film). Dn, f, w (C; Ctr) = 61 (-1; -4) dB (with a connection that is flexible in bending) Wall element: RW (C; Ctr) = 48 (-2; -7) dB (applies to the depicted wall construction with a panel cavity thickness (stud depth) ≥ 300 mm according to test results from ift Rosenheim) Reinforced concrete slab: RW = 67 dB; Ln, w = 37 dB Sound insulation values of the floor slab do not take into account flanking sound transmission. They apply only to the depicted construction, 260 mm thick, ­floating screed with m' ≥ 140 kg/m2 and impact sound ­insulation board with s' ≤ 20 MN/m3 (in accordance with DIN 4109-2, DIN 4109-32 and DIN 4109-34).

Uwall element = 0.15 W/m2K

The wall construction fulfils the requirements of up to and including building class 3 without additional measures. So that it complies with the requirements for building classes 4 and 5, the core element must have a fire-resistance rating of 30 minutes (EI 30). In Germany, verification of usability must be provided for the core element construction (e.g. DIN 4102-2). For building classes 4 and 5, timber external wall cladding must limit the spread of fire, therefore the ­facade system must comply with the German reaction to fire classification of “flame-retardant” (A1, A2 or B1 in accordance with the German classification system). These arrangements effectively suppress fire propagation across the facade. The design must also consider secondary fire paths in the area of the joint.

In order to achieve the low energy standard, thermal bridging must be analysed accurately because, in the case of inserted wall elements, the connection creates a constructional thermal bridge and its great length can be problematic.

55

Floor Slab Joint With Access Balcony

13.

8.

7.

5.

4.

6. 9. 2.

1.

8.

3.

2.

56

11. 10.

Installation and Joint Construction

1. F  ix insulation strip in accordance with EN 13 162 (melting point > 1,000 °C) onto front edge of slab shortly before installing lower external wall element 2. F  asten the steel angle to the top rail of the lower external wall element and install the external wall element 3. P  osition lower reinforced concrete precast column of access balcony 2 cm in front of the lower external wall element 4. Install reinforced concrete precast (PC) floor of access balcony at appropriate height above reinforced concrete floor

12.

9.

slab to avoid a threshold at the exit; connect precast floor to column units using dowels; the elastomeric bearings allow for height adjustment at the PC floor to column joint 5. Install the upper external wall element 6. C  reate a windtight layer by gluing on the facade membrane (sd ≤ 0.3 m) 7. P  osition the upper PC column on the elastomeric bearing and make the dowel connection 8. Install the facade system (in this case: ventilated facade, air gap interrupted

 at each floor); the facade has recesses in the area of the PC columns   9. Ensure air and smoketightness (at top and underside) with self-adhesive tape 10. Apply ceiling plaster or fill voids at the reinforced concrete slab /wall corners 11. Construct the services cavity (here free-standing, using steel profiles) 12. S  eal continuously the gypsum plasterboard type DF joints at the wall, ceiling and floor to improve sound insulation in accordance with EN 15 651-1 13. Install floor construction

External Wall Joints – Horizontal Joints

Installation of the external wall elements alternates with the installation of the re­ inforced concrete precast units. The precast concrete floor units of the access balcony are connected at intervals by load-bearing thermal insulation elements to the reinforced concrete floor slabs (see Fig. 3, p. 50). Dowels connect the PC columns and PC floor units of the access balcony. In the area of the exit door, the threshold height can be locally reduced to allow barrier-free access to the balcony. The timber external wall must be adequately sealed against moisture (installation of a drainage layer, if necessary

connected to a water outlet plate). To avoid costly driving rain protection or structural wood protection, it makes sense to cover the access balcony, which also protects the area of the joint from the direct effects of the weather. The ­free-­standing (decoupled) wall lining ­enhances sound insu­lation. Ventilation, ­cavity closed at top (instead of rear ­ventilation, cavity open at top) of the ­facade prevents fire propagation and ­reduces the amount of smoke generated. In other respects, the notes for the “floor slab joint, self-supporting external wall ­elements” apply (see p. 52f.).

Vertical section  Scale  1:10  1 T  imber panel construction element: 16 mm facade board in accordance with fire ­protection requirements (e.g. painted cement-­ bonded particle board) 30/50 mm timber lath subconstruction (e.g. spruce) staggered butt joints, ventilated 15 mm gypsum fibreboard with facade membrane (windtight layer) vapour-permeable (sd ≤ 0.3 m) 260 mm solid structural timber (KVH) (a = 62.5 cm stud spacing), 2≈ 130 mm thermal insulation filling (WLS 040) 18 mm OSB board (airtight layer) 20 mm air gap 40 mm services cavity consisting of CW 40 steel profile subconstruction, thermal ­insulation filling (WLS 040) 2≈ 12.5 mm gypsum plasterboard type DF (GKF)   2 Floor construction: 12 mm floor covering 70 mm cement screed 0.2 mm PE film separating layer 30 mm impact sound insulation (WLS 045) 20 mm thermal insulation (WLS 040) 260 mm reinforced concrete slab with 30 mm insulation strips (WLS 040) in front of the floor slab edge 10 mm plaster   3 Precast reinforced concrete floor unit access ­balcony   4 Force-transmitting joint (windtight) between the bottom  and top rails   5 Reinforced concrete PC columns with 2≈ 10 mm elastomeric bearings and dowel connections   6 Concrete anchor bolt /screw with plain washer (e.g. M 12)   7 Steel angle (cut to size S 235)   8 Glued membrane (air and smoketightness)   9 2≈ 3 wood screws (e.g. full thread screw (VGS) 8.0 ≈ 160 mm) with spacer sleeves and elongated holes 10 Flexible joint seal

1

2%

6 7

3 4

8

2

9

10 5

8

Sound Insulation

Thermal Insulation and Moisture Protection

Fire Protection

Dn, f, w (C; Ctr)= 65 (-2;-7) dB

Uwall element = 0.15 W/m2K

Wall element: RW (C; Ctr) = 48 (-2; -7) dB Wall with 62.5 cm stud spacing; stud depth ≥ 300 mm (in accordance with test values from ift ­Rosenheim)

The height of the bottom and top rails should be kept to the minimum required for structural purposes to ­reduce potential thermal bridging.

The access balcony acts as an escape route in the event of a fire. If it acts as an escape route only in one direction (to a stairwell), then the facade cladding must be “non-combustible” in Germany. If the access balcony provides escape routes in two directions, then the facade is constructed to meet the requirements of the building class. In ­addition, a fire protection concept should be drawn up that clearly demonstrates compliance with fire protection requirements. The design must also consider secondary fire paths.

Reinforced concrete slab: R  W = 67 dB Ln, w = 37 dB Sound insulation values (not including secondary ­transmission paths) apply specifically to the depicted construction, if constructed with floating screed m' = 140 kg/m2 and impact sound insulation board s' = 20 MN/m3 (in accordance with DIN 4109-32, ­sections 4.1.4.2.2 & 4.8.4.4 and DIN 4109-34).

57

Base Joint With Timber Bottom Rail Beyond the Splash Water Zone

Vertical load is transferred by contact pressure, with the mortar bed able to compensate for any differences in level. If necessary, this can also be accomplished with a suitably shaped bottom rail. The element is connected to the reinforced concrete base using a steel angle. If a rear-ventilated (continuous air gap) or ventilated facade (air gap interrupted at each floor) is used and the bottom rail is also beyond the splash water zone, then a 30-cm wide bed of gravel in accordance with DIN 68 800-2 Image A.11 is provided.

7.

5.

6.

3.

8.

2.

1.

4.

Installation and Joint Construction

1. F  asten the steel angle to the reinforced concrete floor slab, incorporating airtight film 2. Install a levelling layer (cement mortar and spacer pieces) and then install the external wall element (test airtightness in the area of the joint); the final level of the underside of the base floor 58

threshold (building class 0) must be at least 15 cm above the surrounding ground 3. A  pply the building waterproofing layer in accordance with DIN 18 533 4. A  pply the base insulation and seal the joint with joint sealing tape 5. Apply render

6. Construct the services cavity (here using horizontal laths) 7. Install floor construction 8. Fill with drainage media and /or install a gravel bed; construct terrace external works or surrounding ground ­surface

External Wall Joints – Horizontal Joints

Vertical section  Scale  1:10

1

3 5

≥150 mm

 1 T  imber panel construction element: Thermal insulation composite system (with ­approval for construction use) consisting of 8 mm plaster 60 mm fibre insulation board (WLS 045) 16 mm MDF board (windtight layer) vapour-­ permeable 160 mm solid structural timber (KVH) (a = 62.5 cm stud spacing), thermal insulation filling (WLS 040) 15 mm OSB board (airtight layer) 60 mm services cavity with solid structural timber (KVH) subconstruction (a = 62.5 cm stud spacing), thermal insulation filling (WLS 040) 2≈ 12.5 mm gypsum plasterboard type DF (GKF)   2 Floor construction: 12 mm floor covering 70 mm cement screed 0.2 mm PE film separating layer 30 mm impact sound insulation (WLS 045) 40 mm thermal insulation (WLS 040) 5 – 8 mm seal 300 mm reinforced concrete floor slab 200 mm perimeter insulation (WLS 040) 50 mm blinding layer   3 15 – 30 mm levelling layer (force-transmitting bearing layer under bottom rail) with spacer ­pieces and cement mortar   4 Base area with base render 200 mm make-up piece perimeter insulation (WLS 040) Waterproofing 300 mm reinforced concrete 200 mm perimeter insulation (WLS 040)   5 Base rail   6 Steel angle (e.g. L125/75/12 mm, S 235)   7 Glued membrane (air and smoketightness)   8 Concrete anchor bolt /screw with plain washer (e.g. M 12)   9 2≈ wood screws (e.g. full thread screw (VG) 8.0 ≈ 140 mm) 10 Flexible joint seal (e.g. joint sealing tape), applied on site

10

6 7

2

9

8

4

Sound Insulation

Thermal Insulation and Moisture Protection

Fire protection

No special requirements apply.

Ucomponents = 0.15 W/m2K

Wall element: RW (C; Ctr) = 45 (-1; -6) dB (applies to the depicted wall construction in ­accordance with DIN 4109-33, Table 6, line 6)

The base insulation should be as thick as possible and the laths in the services cavity positioned at a ­distance from the reinforced concrete floor slab to ­reduce thermal bridging. Optimum design for thermal insulation: thermal resistance in the area of the base insulation should be about equal to that of the external wall.

For German building classes 4 and 5, the core ­element requires a verification of usability for its fire resistance. In addition, the materials in the facades for building class 4 and 5 must limit the spread of fire, therefore the facade system must comply with the German reaction to fire classifi­cation of “flameretardant” (A1, A2 or B1 in accordance with the German classification system). There are no further special fire protection requirements applicable to the connection.

59

Base Joint at Ground Level

A ground-level base joint (underside of the bottom rail in the splash water zone) is required for example in the area of an exit onto a terrace. This can be constructed in accordance with DIN 68 800-2 using a metal grid and a gravel bed (underside of bottom rail to top of gravel bed ≥ 15 cm). As an alternative, a concrete plinth can be used if the ground level joint is not only at discrete points (e.g. in the area of a terrace) but extends completely around the building. In the case of a ventilated (air gap interrupted at each floor) or rear-ventilated facade (continuous air gap), wood should be protected by adequate constructional measures, such as installing a render carrier board on the base in the splash water zone (e.g. extruded polystyrene (XPS)).

7.

6.

8. 4. 5.

3.

2.

1.

Installation and Joint Construction

1. F  asten the steel angle to the reinforced concrete floor slab, incorporating airtight film 2. Install a levelling layer (cement mortar and spacer pieces) and then install the external wall element (test airtightness in the area of the joint) 60

3. A  pply the building waterproofing layer in accordance with DIN 18 533 4. A  pply the base insulation (make-up piece) and seal the joint with joint ­sealing tape 5. Apply render 6. C  onstruct the services cavity

(here using horizontal laths) 7. Install floor construction 8. Fill with drainage media and /or install a gravel bed; construct terrace external works or surrounding ground ­surface

External Wall Joints – Horizontal Joints

Vertical section  Scale  1:10

1

3 5

≥150 mm

 1 T  imber panel construction element: Thermal insulation composite system (with ­approval for construction use) consisting of 8 mm plaster 60 mm fibre insulation board (WLS 045) 16 mm MDF board (windtight layer) vapour-­ permeable 160 mm solid structural timber (KVH) (a = 62.5 cm stud spacing), thermal insulation filling (WLS 040) 15 mm OSB board (airtight layer) 60 mm services cavity with solid structural timber (KVH) subconstruction (a = 62.5 cm stud spacing), thermal insulation filling (WLS 040) 2≈ 12.5 mm gypsum plasterboard type DF (GKF)   2 Floor construction: 12 mm floor covering 70 mm cement screed 0.2 mm PE film separating layer 30 mm impact sound insulation (WLS 045) 40 mm thermal insulation (WLS 040) 5 – 8 mm seal 300 mm reinforced concrete floor slab 200 mm perimeter insulation (WLS 040) 50 mm blinding layer   3 15 – 30 mm levelling layer (force-transmitting ­bearing layer under bottom rail) with spacer ­pieces and cement mortar   4 Base area with drainage board Base render 200 mm make-up piece perimeter insulation (WLS 040) Waterproofing 300 mm reinforced concrete 200 mm perimeter insulation (WLS 040)   5 Base rail   6 Steel angle (e.g. L125/75/12 mm, S 235)   7 Glued membrane (air and smoketightness)   8 Concrete anchor bolt /screw with plain washer (e.g. M 12)   9 2≈ wood screws (e.g. full thread screw (VG) 8.0 ≈ 140 mm) 10 Flexible joint seal (e.g. joint sealing tape), applied on site

6

7

2

9

10

8

4

Sound Insulation

Thermal Insulation and Moisture Protection

Fire Protection

No special requirements apply.

Ucomponents = 0.15 W/m2K

Wall element: RW (C; Ctr) = 45 (-1; -6) dB (applies for the depicted wall construction in ­accordance with DIN 4109-33, Table 6, line 6)

The base insulation should be as thick as possible and the laths in the services cavity positioned at a ­distance from the floor slab to reduce thermal bridging.

For German building classes 4 and 5, the core element requires a verification of usability for its fire resist­ance. In addition, the materials in the facades for b ­ uilding class 4 and 5 must limit the spread of ­fire, therefore the facade system must comply with the German reaction to fire classification of “flame-­ retardant” (A1, A2 or B1 in accordance with the German classification system). There are no further special ­fire protection requirements applicable to the joint.

61

Flat Roof Joint

The detail shows a non-accessible flat roof with bituminous waterproofing. For the best results, the joint should be installed without a butt joint between the external wall elements. Depending on the parapet height, the standard panel height of 3.50 m can be manufactured and transported in extended heights up to 3.80 m. The possible maximum height of the panel depends on the national transport regulations. The external wall element is connected to the reinforced concrete roof slab using a steel angle. The threaded fastener is not positioned in the top rail but in the studs, which are made wider (≥ 8 cm) to allow this. To satisfy the structural engineering requirements, two or three full-thread screws are required, one above the other. Alternatively, the panel can be fastened to a horizontal inter­ mediate beam. However, this will require additional verification of structural adequacy. To avoid the chimney effect in the event of a fire, a ventilated (closed at top) facade is preferred to a rear-ventilated (open at top) facade. This results in the external cladding terminating flush up to the parapet wall coping. Weather protection must also be ensured for the building during construction.

5.

1.

2.

4.

9.

6.

8.

3. 7.

Installation and Joint Construction

1. F  asten the steel angle to the reinforced concrete floor slab 2. G  lue the insulation strip in accordance with EN 13 162 (melting point > 1,000 °C) onto the front edge of the slab shortly before installing the external wall ­elem­ent 3. Install the external wall element (including pre-attached cladding) 62

4. Install the facade system (here: ventilated facade, closed at top) 5. Install the flat roof waterproofing and insulation in accordance with DIN 18 531 with metal sheet waterproofing of the parapet; apply adhesive airtight covering to steel angle 6. Seal to make air and smoketight 7. A  pply ceiling plaster or fill voids at

the reinforced concrete roof slab / wall corners. 8. Construct the services cavity (here using horizontal laths) 9. Seal continuously the gypsum plasterboard type DF joints at the wall and ceiling to improve sound insulation in accordance with EN 15 651-1

External Wall Joints – Horizontal Joints

3

Vertical section  Scale  1:10 1

2

3

4 5 6 7 8

 imber panel construction element: T 24 mm timber external wall cladding (e.g. larch) 30/50 mm timber lath subconstruction (e.g. spruce) staggered butt joints, ventilated 15 mm gypsum fibreboard with facade membrane (windtight layer) vapour-permeable (sd ≤ 0.3 m) 220 mm solid structural timber (KVH) (a = 62.5 cm stud spacing), 2≈ 110 mm thermal insulation filling (WLS 040) 15 mm OSB board (airtight layer) 60 mm services cavity consisting of solid structural timber (KVH) (a = 62.5 cm stud spacing), thermal insulation filling (WLS 040) 2≈ 12.5 mm gypsum plasterboard type DF (GKF) Roof construction: 2≈ 4 mm waterproofing membrane (2-layer) Mineral fibre thermal insulation (WLS 035) laid to falls of 120 mm + 100 mm in middle 4 mm separating layer and vapour barrier Bitumen primer 240 mm reinforced concrete roof slab with 30 mm insulation strips in front of the slab edge 10 mm plaster Metal sheet waterproofing to parapet chamfered on site, including attachment of adhesive facade waterproofing (in the factory) Parapet closure piece, shaped timber Steel angle (e.g. ∑ 200/16 mm, S 235) Glued membrane (air and smoketight) Concrete anchor bolt /screw with plain washer (e.g. M 12) 3≈ wood screws (e.g. full thread screw (VGS) 8.0 ≈ 140 mm) with spacer sleeves and elongated holes Flexible joint seal

4

6

5

2

7

8 5 1

Sound Insulation

Thermal Insulation and Moisture Protection

Fire Protection

Wall element: RW (C; Ctr) = 47 (-2; -7) dB (applies to the depicted wall construction with a panel cavity thickness (stud depth) ≥ 160 mm according to test results from ift Rosenheim)

Uwall element = 0.15 W/m2K

For German building classes 4 and 5, the core ­element requires a verification of usability for its ­fire resistance. The materials in the facades for building class 4 and 5 must limit the spread of fire, therefore the facade system must comply with the German reaction to fire classification of “flame-­ retardant” (A1, A2 or B1 in accordance with the German classification system). The top coating of the roof must be constructed so that flying sparks cannot cause a fire. According to German building laws, the required fire resistance of the roof ceiling depends on the building class and the layout of the top floor.

The gap between the reinforced concrete roof slab and the laths in the services cavity reduces thermal bridging.

63

4 5

Vertical Joints – General Requirements and Guidance The vertical joints between the external wall elements in hybrid construction, i.e. the joints in the vertical direction of building components such as reinforced concrete walls and columns, are less important structurally than their horizontal joints. In the structural idealisation, the application and transmission of selfweight and wind loads from the external walls to the foundations takes place through the horizontal joints their ends make with the floor slabs or the wall ­elements below them and not through separating walls or columns. Therefore, no structurally relevant connections are required along the vertical joints to sep­ arating walls and columns other than those necessary to keep the components in position. Installation and joint construction is similar to that for the floor slab butt joints. For sound insulation reasons, external wall elements should, for example, be decoupled from one another where they connect to separating walls within and between the residential units. This will considerably reduce flanking sound transmission. It can be ensured by attaching an elastic sound insulation layer within the element butt joint (Fig. 4). Windtightness can be achieved in rear-ventilated (continuous air gap) or ventilated (air gap interrupted at each floor) facades by applying a facade membrane. Enhanced sound and fire protection requirements apply to connections made to residential separation or stairwell walls, resulting in a need for higher quality constructional measures. Thus, the example shows the connection of a separating wall to a firewall (permis­ sible up to German building class 5, see Fig. 10, p. 38 and p. 66f.). Firewalls are 64

 ecoupled element butt joint at the internal /  D external wall with elastic insulation strips (horizontal section) Fire protection requirements for load-bearing ­external walls for different building classes 4

normally designed to be load-bearing. In accordance with German building laws (§ 30 MBO), firewalls are there to separate buildings from each other or to divide a building into fire compartments. As room-­ enclosing walls, they must prevent the spread of fire to other buildings or other sections of the same building for an ad­ equate period. Therefore, firewalls must be fire-resistant under additional horizontal mechanical loads and be constructed from non-combustible materials. However, exceptions apply for German building classes 1– 3 and 4. In the case of building class 4, instead of being classified as REI 90-M (F 90+M), firewalls need only to be classified as REI 60-M (F 60+M). When these reductions apply, such firewalls are described as “firewall replacement walls” in Germany. At the same time, all building components in buildings up to class 5, including firewalls with additional mechanical loading, can be constructed in timber with fire-resistance ratings up to REI 90-K260. However, they must be tested and classified for such use. Depending on the rules in the relevant state building regulation, an application for modification may be required for the approval. Fire protection classifications are based on the currently applicable version of EN 1995-1-2 [1] (including the national appendix) and DIN 4102-4 [2]. In addition, official test results that are used to classify building elements are available from German ­construction material suppliers or timber construction companies [3]. Firewalls or “firewall replacement walls” (internal wall, at right angles to the timber panel construction external wall) in hybrid construction should be constructed in e.g. reinforced concrete, since firewalls are generally part of the load-bearing structure. In hybrid construction, the ­connection of room-enclosing, non-loadbearing external walls and firewalls must

be designed particularly carefully. A sensible approach is to integrate the reinforced concrete firewall or firewall replacement wall within the plane of the timber panel construction external wall. In doing so, the function of the firewall must be ensured up to the front edge of the external wall. To ensure adequate thermal insulation, the front edge of the wall must be void-free and form a positive connection to a non-combustible mineral wool insulation layer (melting point >1,000 °C). As does the reinforced concrete, this arrangement fulfils the fire protection requirements across the width of the firewall. This would prevent an untimely fire starting in the combustible timber construction in the area of the connections. In addition, no enhanced requirements apply to the external wall to the left and right of the firewall. The table on the right shows the fire protection requirements for each German building class (Fig. 5). More detailed information is contained in the section on “Fire Protection” (p. 37ff.). In Germany, a project-specific fire protection concept clearly demonstrating ­compliance with the requirements must be prepared in the case of building classes 4 and 5. The concept identifies the escape routes to be kept free of smoke, such as external stairwells or access balcon­ies, as well as well-­ arranged smoke and fire compartments. Fire alarms can substantially improve the protection of life in the event of fire [3]. In the case of ETICS in building classes 4 and 5, fire protection is ensured for the facade through the use of “fire-retardant” insulation boards (e.g. mineral wool insulation boards). Timber cladding does not achieve the required “flame-retardant” rating for the facade without additional measures. Here, special construction measures may be required to achieve the protec-

External wall joints – vertical joints

Building class Facade

Non-load-bearing external wall (§ 28 MBO – German Model Building Code) Core element

Curtain wall

   1 to 3

No requirements

No requirements

No requirements

   4 and 5

The facade materials must be at least “flame retardant” (A1, A2 and B1 in accordance with the German classification system) in order to limit fire spread across the facade.

In Germany, a verification of usability in accordance with DIN 4102-2 [6] etc. must be ­provided to demonstrate a fire-resistance rating of 30 minutes (EI 30)1)

No requirements

Secondary fire paths in the area of the joint must be considered  riterion E – Etanchéité – Integrity C Criterion I – Isolation – Thermal insulation (limits the temperature rise)

1) 

5

tion goal of flame retardance where ­combustible materials have been used. This protection goal ensures that the fire cannot spread outside the initial fire area without external influence. A series of suggestions for constructional measures based on extensive research in ­Switzerland, Austria and Germany are available [4], [5]. These suggestions can be used when drawing up fire protection concepts. The ven­tilation cavity should be compartmentalised for each storey and the blind facade boarding designed to be free of openings. The blind facade boarding incorp­orates projections, which can be formed using steel sheets. As with moisture protection, solutions for fulfilling fire protection requirements can be created using constructional measures. On environmental grounds, fire-retardant chem­ icals should not be used on the building exterior. [3] Cabling and pipework should be routed away from where they could affect firewalls. If cabling or pipework must be placed in the core element of the external wall, then in Germany the provisions of the Model Cabling Systems Guideline (MLAR), also known as the Guideline for Fire Protection Requirements on Cabling Systems (RbALei), should be followed. The differing requirements in some German states need also to be considered. Other countries have similar guidelines or regulations. Cabling in the services cavity does not usually present a problem, if it is not needed for the fire-resistance classification of the building element. Terminating a reinforced concrete firewall within the thickness of the non-loadbearing timber frame construction external wall undoubtedly increases thermal bridging, however, this is justifiable in fire protection terms to protect people from injury and loss of life. Fire protection takes precedence over thermal insulation.

Because this connection detail is usually limited in scope and a linear feature on the building, it plays a subordinate role in the thermal insulation performance of the building. Set out below is further information about the building physics of the fire protection connection detail shown on the following page (p. 66f.): Thermal Insulation: • U-values and information about redu­ cing thermal bridges Sound Insulation (according to the German technical standards): • Weighted sound reduction index and spectrum adaptation terms Rw (C, Ctr) • Weighted normalised impact sound pressure level and spectrum adaptation term Ln, w (CI) and • Weighted normalised flanking level difference and spectrum adaptation terms Dn, f, w (C, Ctr) The spectrum adaptation terms C, Ctr and CI are not required for verification in accordance with DIN 4109.

Notes: [1] DIN EN 1995-1–2: 2010 -12, Eurocode 5: Design of timber structures – Part 1–2: General – Struc­ tural fire design; German version EN 1995-1–2: 2004 + AC: 2009 [2] DIN 4102-4: 2016-05: Fire behaviour of building materials and building components – Part 4: ­Synopsis and application of classified building materials, components and special components (in German) [3] Winter, Stefan: Der zeitgenössische Holzbau, Brandschutz im Hochbau. In: Urbaner Holzbau. Handbuch und Planungshilfe. Chancen und ­Potentiale für die Stadt. Pub. Cheret, Peter; Schwaner, Kurt; Seidel, Arnim. Berlin 2013 (in German) [4] Winter, Stefan; Merk, Michael: Brandsicherheit im mehrgeschossigen Holzbau. Abschlussbericht Teilprojekt 2. High-Tech-Offensive Zukunft Bayern. Technical University Munich, Chair of Timber Structures & Building Construction. Munich 2008 (in German) [5] Schober, Peter et al.: Fassaden aus Holz. 3rd ­edition, Vienna 2014 (in German)

Fire Protection (according to the German building code): •  Guidance on fire protection Further information about standards can be found in the Appendix (p. 94).

65

Firewall and Firewall Replacement Walls

Load-transmitting connection of the timber frame construction elements takes place at the horizontal butt joints. In add­ ition, the elements can be held in position vertically by suitable constructional mea­ sures that take into account sound insulation. A firewall or “firewall replacement wall” in accordance with DIN 4102-4 [1] must continue to function as such and ­fulfil fire protection requirements right up to the outside edge of the external wall. Apart from that, and the requirements relating to building classes, no special requirements apply to the layered construction of the external wall element in Germany. A ventilated facade (air gap interrupted at each floor) retards fire spread, reduces the amount of smoke generated and is therefore preferable to a rear-ventilated facade (continuous air gap).

9. 8. 6.

7.

7.

1.

[1] DIN 4102-4:2016-05: Fire behaviour of building materials and building components – Part 4: ­Synopsis and application of classified building materials, components and special components (in German)

2.

3. 4. 5.

Installation and Joint Construction

1. G  lue the insulation strip in accordance with EN 13 162 (melting point > 1,000 °C) onto the reinforced concrete wall 2. Install the external wall elements 3. Install the windtight layer (facade membrane sd ≤ 0.3 m) 4. Install the facade cladding (here: 66

­ventilated facade, closed at top) 5. Install the non-flammable external wall cladding in the area of the firewall (or firewall replacement wall) (e.g. thin steel plate). 6. S  eal to make air and smoketight (both sides) 7. A  pply ceiling plaster or fill voids at

the reinforced concrete wall corner 8. Construct the services cavity 9. Seal continuously the gypsum plasterboard type DF joints at the wall, ceiling and floor to improve sound insulation in accordance with EN 15 651-1

External wall joints – vertical joints

Horizontal section  Scale  1:10 1

2

3

4 5

 imber panel construction element: T 16 mm facade board (e.g. painted cement-bonded particle board) 30/50 mm solid structural timber (KVH) sub­ construction (e.g. spruce) staggered butt joints, ventilated (closed at top) 15 mm gypsum fibreboard with facade ­membrane (windtight layer) vapour-permeable (sd ≤ 0.3 m) 220 mm solid structural timber (KVH) (a = 62.5 cm stud spacing), 2≈ 110 mm thermal insulation filling (WLS 040) 15 mm OSB board (airtight layer) 60 mm services cavity consisting of CW 60 steel profile subconstruction, thermal insulation filling (WLS 040) 2≈ 12.5 mm gypsum plasterboard type DF (GKF) Plaster finish Firewall (or firewall replacement wall): 10 mm plaster 250 mm reinforced concrete wall 10 mm plaster Cladding in the area of the firewall, non-flammable (e.g. metal sheets) Windtight layer (glued-on facade membrane) Thermal insulation (void-free) both sides and in front of the edge of the timber panel construction elements (≥ 20 mm) Glued membrane air and smoketight (both sides) Flexible joint seal (both sides)

2

4

5

1

3

Sound Insulation

Thermal Insulation and Moisture Protection

Fire Protection

Dn, f, w (C; Ctr) = 66 (-2; -8) dB

Uwall element = 0.15 W/m2K

External wall element: RW (C; Ctr) = 47 (-2; -7) dB (applies to the depicted wall construction with a panel cavity thickness (stud depth) ≥ 160 mm according to test results from ift Rosenheim)

The degree of insertion of the firewall necessary for fire protection reasons increases the effect of ­thermal bridging; this is compensated by constructional measures using the lateral insulation strips.

The firewall must continue to function as such to the outside edge of the external wall. This is ­ensured by installing non-combustible insulation strips to form a positive connection and metal sheets as external wall cladding. In addition, the external wall is subject to the ­German fire protection requirements in accordance with the applicable building class.

Reinforced concrete wall, plastered: RW = 64 dB (in accordance with DIN 4109-32, clause 4.1.4.2.2)

67

Kopfzeile ‡‡‡

Example Projects

70 “Aktivhaus” – Multistorey Apartment Building in Frankfurt am Main HHS Planer + Architekten, Kassel 76 Experimental Residential Buildings in Wuppertal-Ostersiepen ACMS Architekten, Wuppertal 82 “Ecoleben” – Multistorey Residential Buildings in Penzberg Lang Hugger Rampp Architekten, Munich and Krämmel Bauplan, Wolfratshausen 86 35 New Subsidised Housing Units in Freising A2freising architekten + stadtplaner, Kai Krömer and Stefan Lautner, Freising

69

“Aktivhaus” – Multistorey Apartment Building in Frankfurt am Main

Architects: HHS Planer + Architekten, Kassel Structural engineers: B+G Ingenieure, Bollinger und Grohmann, Frankfurt am Main Timber construction: Gumpp & Maier, Binswangen Reinforced concrete: Ed. Züblin, Frankfurt am Main Completion: 2015

74 two to four-room apartments were completed on a narrow piece of land ­formerly used as a car park and long held to be unsuitable for development. Four single-­flight stairways on the northern side give access to the apartments. The ground floor has two retail units and a public car-­sharing station for electric vehicles, which are charged using the excess electricity produced by the building’s own photo­voltaic systems. The Aktivhaus is the first multistorey apartment building in Germany to achieve the German Effizienzhaus Plus standard and is designed to produce more energy from

70

within its own footprint over the course of a year than its residents consume. ­Photovoltaic modules on the roof and facade produce the electricity; a heat pump supplies the energy for heating from the city’s wastewater. The building is a reinforced concrete crosswall structure with prefabricated ­timber panel construction elements. The extensive glazing covering the south facade has a 62 % window-to-wall ratio, with photovoltaic modules in front of the opaque parts. The balustrades on the south side and the opaque elements on the north facade are clad with fibre-­

cement boards. The project provides an excellent example of the advantages of hybrid construction: the reinforced concrete structure makes it much simpler to comply with fire and sound protection requirements and to construct the 150-m long building, which is only 10 m deep. The timber panel construction elements offer a highly insulated external wall with a comparatively thin cross section. The prefabricated facade components arrived on a “just-in-time” basis. With a site crane lifting the elements into position, the installation was quick, clean and quiet.

“Aktivhaus” in Frankfurt am Main

aa

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Location 1plan  Scale  1:3000 Section  Layout plan of standard storey  Scale 1:800 3 Examples of apartment layout plans  Scale 1:250

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Room Balcony Corridor Living / eating space Loggia

4 2

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71 1

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“Aktivhaus” in Frankfurt am Main

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South facade Vertical section of roof terrace and window / balustrade Horizontal section of photovoltaic cladding Scale 1:20   1 Roof construction: 45 mm monocrystalline photovoltaic module black 80 mm aluminium subconstruction EPDM sealing layer 40 mm laminated veneer lumber Plastic sealing layer 25 mm OSB board 160/280 mm glued laminated timber beam 30 mm 3-ply spruce plywood   2 450 mm cellulose thermal insulation Vapour barrier 200 mm reinforced concrete slab 10 mm plaster   3 Triple-glazed wood-aluminium window   4 2≈ 15 mm laminated safety glass anti-fall barrier   5 8 mm fibre cement board balustrade cladding   6 25 mm pine boarding heat-treated grooved on subconstruction   7 EPDM sealing layer Thermal insulation PUR sloped ≤ 30 mm 60 mm thermal insulation vacuum insulation ­panels Polymer bitumen waterproofing membrane 300 mm reinforced concrete slab 10 mm plaster   8 Floor construction: 22 mm vertical finger parquet, oak 65 mm heating screed PVC sheeting 75 mm impact sound insulation 280 mm reinforced concrete slab 10 mm plaster   9 Timber panel construction element: 15 mm wood fibreboard, moisture-resistant 60/300 mm glued laminated timber studs, with cellulose thermal insulation fill 15 mm OSB board 10 2≈ 12.5 mm gypsum plasterboard Metal studs, with 50 mm mineral wall thermal ­insulation fill 20 mm air gap 11 35 mm monocrystalline photovoltaic module black Rear ventilation

73

20 mm air gap   5 Timber panel construction element: 15 mm wood fibreboard vapour-permeable, moisture-resistant 60/300 mm glued laminated timber studs, with cellulose thermal insulation fill 15 mm OSB board   6 8 mm fibre-cement board Rear ventilation /40 mm timber lath subconstruction   7 Element butt joint   8 60/300 mm glued laminated timber   9 Precompressed sealing tape 10 Scaffold anchors at max. 2.50-m spacing 11 100/300 mm glued laminated timber with 3≈ 6/160 countersunk head screws 12 170 mm mineral wool thermal insulation

Floor slab butt joint North facade Scale 1:5 1

2 3 4

Floor construction: 22 mm vertical finger parquet, oak 65 mm heating screed, PVC sheeting 75 mm impact sound insulation 220 mm reinforced concrete slab 10 mm plaster M12≈70 anchor bolt 360/100/5 mm steel plate chamfered with hole for Ø 14 mm anchor bolt 2≈ 12.5 mm gypsum plasterboard Metal studs, with 50 mm mineral wool thermal insulation fill

13 Aluminium slatted outdoor blind 14 20 mm mineral wool thermal insulation strip 15 15 mm wood fibreboard, moisture-resistant 16 60/170 mm solid structural timber (KVH) 17 10 mm joint sealing tape 18 Galvanised metal angle fire stop, every second storey 19 19 mm wood-based board melamine-coated anthracite grey 20 Self-adhesive tape for airtight seal 21 Aluminium L profile 22 300 mm cellulose thermal insulation 23 19 mm ventilation duct with insulation 24 Ventilation grid 25 Supply air duct

4 6

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“Aktivhaus” in Frankfurt am Main

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75

Experimental Residential Buildings in Wuppertal-Ostersiepen C

A

B

Architects: ACMS Architekten, Wuppertal Structural engineers: T/S/B-Ingenieurgesellschaft, Darmstadt Timber construction: Holzbau Brüggemann, ­Neuenkirchen Reinforced concrete: Läer+Rahenbrock, Siegburg Completion: 2012

The three multifunctional residential buildings have increased the building density on the University of Wuppertal campus to meet the rising demand for student accommodation. However, they could also become usable and attractive for the general housing market in the future, as the floor layout of the flats can be converted into three-­person apartments with little effort. The Ministry of Economic Affairs, Building, Housing and Transport for the state of North Rhine-Westphalia funded the project as “experimental residential buildings”. The buildings have minimum intrusion into the steeply sloping ground and form an ensemble of compact, rotated

76

structures. All residents benefit from the views, passive solar energy and high-­ quality outdoor surroundings. The division of space within the buildings and their positioning on level areas of the slope ­create spatial qualities on what was previously considered to be an undevelopable piece of leftover land. Access to the five floors of the middle building is by an external bridge. The buildings are designed to fulfil the Passivhaus standard. They are configured as reinforced concrete skeleton frames with flat roofs, and the building envelope of large-format, prefabricated timber panel construction elements, each with a length of approximately 15 m. To

suit the specific floor layout plans, the architects adopted a 70-cm spacing of the vertical members for the building instead of the usual 62.5 cm. The studs in the timber panel construction elements are joists, allowing for optimum insulation performance. The rear-ventilated cladding consists of laminated boards in various shades of green. Hybrid construction on this project minimises the use of materials associated with high CO2 emissions, such as concrete. According to the architects, the manufacture and construction of the 2500 m2 building envelope saved 140 t of CO2 emissions in comparison with a traditional reinforced concrete external wall.

Residential Buildings in Wuppertal-Ostersiepen

Layout plan  Scale 1:1000 Section Building B Floor layout standard storey Scale 1:250 1 2 3 4 5 6

1-room flat 2-room flat Access bridge Shared living area with kitchen Room 3-room apartment

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a Buildings A and C: floor layout plan student flats

Building B: access to every floor via an external lift a and bridge Floor layout variants for the student flats

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Buildings A and C: floor layout variants of subsidised residential buildings

Building B: access to every floor via an external lift and bridge Floor layout variants of subsidised residential buildings

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Horizontal section Vertical section Scale 1:20 1

2 3

78

Roof construction: Extensive green roof Substrate approx. 90 mm Filter mat 25 mm solid drainage layer Geotextile liner as protection and reservoir 1.8 mm flexible plastic sealing layer polyolefin 300 mm thermal insulation EPS (WLG 035) 0.5 –1 % slope Vapour barrier bituminous polyolefin sheeting 220 mm reinforced concrete slab 5 –10 mm plaster 50/10 mm steel flat frame galvanised, Ø 12 mm steel bar infill Timber panel construction element:

4 5

8 mm composite resin board rear-ventilated, joint backing 40 mm top-hat profile aluminium subconstruction 16 mm wood fibreboard vapour-permeable, ­water-repellent, tongue and groove Z joist: Bottom rail: 65/65 mm squared timber, 18 mm OSB board web, 100/100 mm squared timber Verticals: 65/65 mm squared timber, 18 mm OSB board web, 65/65 mm squared timber Top rail: 65/65 mm squared timber, 18 mm OSB board web, 100/85 mm squared timber with 260 mm stone wool thermal insulation fill 18 mm OSB board, airtight butt joints glued 12.5 mm gypsum plasterboard, butt joints plaster-­filled French window triple-glazed laminated wood frame

6

7 8 9

Floor construction top floor: 8 mm mosaic parquet, oak 50 mm cement screed Separating layer PE sheeting 20 mm impact sound insulation EPS 220 mm reinforced concrete slab 5 –10 mm plaster 12 mm facade anchor bolt galvanised steel 240/240 mm reinforced concrete column Floor construction ground floor: 8 mm mosaic parquet, oak 50 mm cement screed Separating layer PE sheeting 20 mm impact sound insulation EPS Levelling layer XPS 10 – 20 mm Bituminous elastomer sealing layer, full surface glued 250 mm reinforced waterproof concrete floor slab Separating layer PE sheeting, 500 mm foamed glass aggregate (WLG 080), geotextile

Residential Buildings in Wuppertal-Ostersiepen

1

b

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2 6

7 3

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79

Vertical section element butt joint Horizontal section floor slab Scale 1:5   1 Timber panel construction element: 8 mm composite resin board rear-ventilated, joint backing 40 mm top-hat profile aluminium subconstruction 16 mm wood fibreboard, vapour-permeable, water-repellent tongue and groove Z joist: Verticals: 65/65 mm squared timber, 18 mm OSB board web, 65/65 mm squared timber, with 260 mm stone wool thermal insulation fill 18 mm OSB board, butt joint glued airtight   2 2 mm aluminium sheet anodised   3 Element butt joint   4 Element joint gap subsequently tightly filled with mineral thermal insulation (WLG 035) 16 mm wood fibreboard cover, vapour-­ permeable, water-repellent, movement connection at bottom Gap windtight self-adhesive seal, vapour-permeable Precompressed sealing tape   5 Gap allowing movement   6 French window triple-glazed, laminated wood frame   7 Skirting timber, grey varnished 2 mm sound insulation strips   8 Window self-adhesive seal, airtight, vapour-retardant   9 Facade anchor bolt sealing layer 12 mm facade anchor bolt galvanised steel, grout filling 10 Mineral wool insulation strips in front of slab edge, compressible Rear filling around the anchor with force-­ transmitting attachment to concrete slab to ­prevent slipping 11 Sealing layer, airtight, vapour-retardant, with fold to accept slab deflections of up to 15 mm Timber cover strip between facade / slab allowing movement 12 Floor construction top floor: 8 mm mosaic parquet, oak 50 mm cement screed Separating layer PE sheeting 20 mm impact sound insulation EPS 220 mm reinforced concrete slab 5 –10 mm plaster 13 Element connection oak: 16 mm wood fibreboard, vapour-permeable, water-repellent, tongue and groove, butt joints glued windtight Voids plugged with mineral wool (WLG 035) 14 Corner profile: system profile glued behind ­facade boards 15 Joint with mineral wool (WLG 035), hydrophobic, highly compressible 16 12.5 mm gypsum plasterboard, butt joints filled 17 2≈ 12.5 mm plasterboard 240/240 mm reinforced concrete column 18 Electrical services shaft

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Residential Buildings in Wuppertal-Ostersiepen

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81

“Ecoleben” – Multistorey Residential Buildings in Penzberg

Architects: Lang Hugger Rampp ­Architekten, Munich and Krämmel Bauplan, ­Wolfratshausen Structural engineers: bauart Konstruktions GmbH, Munich Timber construction: Huber und Sohn, Bachmering Reinforced concrete: Krämmel Bauunternehmung, Wolfratshausen Completion: 2018

Five apartment blocks and terraced houses with a total of 57 housing units and a basement parking garage stand on a 7,650 m2 site. The basement connects all the buildings. Two of the apartment buildings are elongated and the others square in plan. The northern block (Building A) was completed as a pilot project for hybrid construction from the ground floor up to and including the second floor with a reinforced concrete frame and a timber panel construction element facade. The set-back top storey is built completely using timber panel construction. The middle standalone square block (Building D) was also built using hybrid construction, while all other buildings were reinforced concrete and masonry structures. The Technical University of Munich consulted on the design. A comparative life cycle analysis for the two square blocks with the same geometries showed, among other things, that the hybrid construction building with a timber external wall uses 13 % less non-renewable primary energy and emits 7 % less CO2-eq. in its production, eventual refurbishment and disposal. The advantages of hybrid construction are even more obvious in the usage phase of the building: the improved thermal insulation for the same wall thickness substantially reduces energy consumption and CO2 emissions resulting from building operation. Building acoustics measurements performed as part of the quality assurance of the construction showed that the hybrid building not only satisfied the minimum requirements in the standard but also largely complied with the requirements for enhanced sound insulation (see p. 42, Fig. 19). Only the impact sound insulation on the tested stairwell landings fulfilled just the minimum requirements. Detailed indoor climate monitoring will track the performance of the completed project. 82

E

D

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A

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“Ecoleben” in Penzberg

Layout plan  Scale 1:2,000 Floor plans • section Building D  Scale 1:250 1 2 3 4 5 6

Room Corridor Living /dining space Balcony Terrace Roof terrace

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Top floor

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Top floor section

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“Ecoleben” in Penzberg

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8 9 Floor plans • section Building A Scale 1:250 Vertical section Building A Scale 1:20

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Roof construction: Photovoltaic modules Subconstruction 0.8 mm aluminium profile sheet 24 mm timber boards 80 mm counter battens Roof liner bituminous membrane 25 mm chipboard 240 mm solid structural timber (KVH) rafters, with thermal insulation fill Vapour barrier 60 mm timber boarding with gaps / battens, with thermal insulation fill  12.5 mm gypsum plasterboard 140/280 mm purlin solid structural timber (KVH) Render Render carrier board Aluminium slatted outdoor blind Triple glazing in plastic frame Balustrade: 60/40/4 mm rail aluminium powdercoated, 60/20/4 mm aluminium bar 10 mm laminated safety glass matt Roof terrace construction: 50 mm concrete paving 50 mm gravel bed 20 mm building protection mat Sealing layer Insulation to falls 2 %, min. 170 mm Vapour barrier 200 mm reinforced concrete slab plastered, painted Fall protection: 60/20/4 mm frame aluminium powdercoated, 40/10/2 mm bars 8 mm thermal insulation composite system 80 mm soft wood fibreboard Timber panel construction element: 12.5 mm gypsum fibreboard 140/60 mm solid structural timber (KVH), with mineral wool thermal insulation fill Vapour barrier 12.5 mm gypsum fibreboard 2≈ 12.5 mm gypsum plasterboard Timber subconstruction, 50 mm thermal insulation fill Floor construction roof storey: 10 mm parquet 70 mm heating screed Separating layer PE sheeting 30 mm impact sound insulation 40 mm thermal insulation 180 mm thermal insulation 200 mm reinforced concrete slab plastered, painted Floor construction upper floor: 10 mm parquet 70 mm heating screed Separating layer PE sheeting 30 mm impact sound insulation 40 mm thermal insulation 200 mm reinforced concrete slab plastered, painted

12

18 13

14 19

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85

35 New Subsidised Housing Units in Freising

Architects: A2freising architekten + ­stadtplaner, Kai Krömer and Stefan Lautner, Freising Structural engineers: Beratende Ingenieure GmbH and Eltschig Tragwerks planung, Freising Timber construction: Gumpp & Maier, Binswangen Reinforced concrete: Xaver Riebel Bauunternehmung, Mindelheim Completion: 2018

The L-shaped building contains 35 sub­ sidised housing units. They are completely wheelchair-accessible and entered from the road-side access balconies. The ­protruding kitchen blocks structure the generously dimensioned access balcony area and create an inviting ambience. On the side facing the street are the bathrooms, while the living rooms and bedrooms as well as the balconies look onto the peaceful green space of the inner courtyard. The southern transverse end block contains the larger family homes. The roof is used as a communal, wheelchair-accessible terrace with raised beds and socialising areas. The building is designed as a reinforced concrete crosswall structure with external walls comprising approximately 1,800 m2 of non-load-bearing timber panel construction elements. The rear-ventilated facades along the access balcony are clad with colour-coated cement-bonded particleboard panels, while rough-sawn timber boards line the facades facing the inner courtyard. The choice of hybrid construction was based on good experiences from earlier projects enabling a short construction time and a high energy standard without the use of thermal insulation composite systems (EIFS or ETICS). Prefabrication unaffected by weather conditions opens the way to achieving an airtight building envelope and a high-­quality facade. The access balconies ­presented a special challenge, both in terms of construction and building physics. Their assembly followed the “Tetris principle”: the timber panel construction elements were installed floor by floor, alternating with the reinforced concrete precast units. The access balcony slabs were attached to the reinforced concrete floor slabs by means of load-­bearing thermal insulation elements. In the area of the exit doors to the access balcony, the top rail was offset downwards to ensure an accessible opening above. 86

Housing Units in Freising

Layout plan Scale 1:2,000 Sections Floor plans Scale 1:400

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 1 Entrance   2 Bicycle storage   3 Access to basement parking garage  4 Store   5 2-room apartment   6 3-room apartment   7 Refuse room   8 Access balcony   9 Communal space 10 Communal kitchen space 11 4-room apartment Ground floor

87

Vertical and horizontal section of inner courtyard facade with horizontal boarding Horizontal section of access balcony facade with cement-bonded particleboard panels Scale 1:20 2

1

3

1

Roof construction: Extensive green roof 90 mm single layer lightweight substrate Drainage layer Building protection mat Plastic sealing layer single sheet, resistant to roots and rhizomes Insulation EPS (WLG 035) sloped 20 – 240 mm 160 mm thermal insulation EPS (WLG 035)

2

3

Bituminous vapour barrier 220 mm reinforced concrete slab Timber panel construction element: 22/130 board cladding spruce painted, tongue and groove horizontal 30/50 mm battens Facade sealing layer sd < 0.1, butt joints glued 15 mm gypsum plasterboard type DF 240/80 mm structural timber (KVH) studs, with cellulose thermal insulation fill 18 mm OSB board 2 mm plastic sealing layer glass non-woven reinforcement, resistant to roots and rhizomes, loosely placed

4

6 c

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Housing Units in Freising

4 5 6

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Triple glazing in wood frame Windowsill wood-based board with laminate 2≈ 12.5 mm gypsum fibreboard Metal studs with 50 mm thermal insulation (WLG 035) fill 20 mm tolerance piece Floor construction: 15 mm multilayer parquet 65 mm cement heating screed Separating layer PE sheeting 20/22 mm impact sound insulation polystyrene rigid foam 30 mm make-up insulation polystyrene rigid foam 220 mm reinforced concrete slab plastered

  8 Fire stop metal sheet galvanised   9 360/100/5 mm steel angle with hole for 14 mm anchor bolt 10 Timber panel construction element: 16 mm cement-bonded particleboard, sanded 30/50 mm battens 40/60 mm counterbattens Facade sealing layer sd < 0.1, 12.5 mm gypsum fibreboard 240/60 mm solid structural timber (KVH) studs, with cellulose thermal insulation fill 18 mm OSB board 11 200/200 mm reinforced concrete PC column

6

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89

Connection details Vertical section access balcony Scale 1:5   1 Housing unit door: 69 mm door leaf timber veneer, coated, insulated core Timber door frame   2 2 mm stainless steel sheet   3 2,135/4,860 mm reinforced concrete PC slab for access balcony, surface slope 2 %, grit-blasted   4 30/10 mm steel grating   5 Element butt joint   6 Timber panel construction element: 16 mm cement-bonded wood particleboard, ­unsanded, painted 40/60 mm battens vertical 30/50 mm battens horizontal, chamfered Facade sealing layer 15 mm gypsum plasterboard type DF 240/60 mm solid structural timber (KVH) studs, with cellulose thermal insulation fill 18 mm OSB board   7 40/30 mm angle expanded aluminium sheet   8 16 mm cement-bonded wood particleboard   9 Access balcony connection with sealing profile 10 2≈ 12.5 mm gypsum fibreboard Metal studs with mineral wool, with thermal insulation fill 20 mm tolerance piece 11 3-zone multifunctional tape 12 Sealing profile as depth stop 13 Acrylic fire protection seal 14 3 ≈ 8 ≈ 240 mm screw, self-tapping 15 Interlocking connection done on site 16 360/100/5 mm steel angle galvanised 17 M 12 anchor bolt

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Appendix

Editors and Authors

Oliver Fischer Prof. Dr.-Ing. Dipl. Wirt.-Ing.

Born 1963 1982–1988 Studied civil engineering at Technical University of Munich (TUM) 1989 –1995 Research associate in the departments of Mechanics & Structural Analysis as well as Structural Engineering (Timber Construction, from 1994) at Bundeswehr University of Munich (UniBwM) 1994 Doctorate (Dr.-Ing.), dissertation in the field of vibration and stability behaviour of slender load-bearing structures (Research Prize 1996 of the Bavarian State Ministry of the Interior, 1996) 1996 – 2009 Bilfinger Berger AG: various engineering and management positions in Germany and abroad, head of design / engineering department from 2003, general power of attorney for civil engineering (worldwide) 1999 – 2009 Lectureship “Design and construction of concrete bridges” at Technical University of Darmstadt 2001– 2009 Lecturer in “Structural ­dynamics and earthquake engineering”, Bundeswehr University of Munich (UniBwM) 2007 Dipl.-Wirt. Ing. (Economics) at ­University of Hagen, Germany since 2009 Full professor of concrete and masonry structures at Technical University of Munich (TUM); Director of the associated Materials Testing Institute (MPA BAU) and the TUM Research ­Laboratory for Engineering Structures since 2011 Publicly appointed independent checking engineer and expert for the whole range of civil structures including buildings, bridges, tunnels, heavy civil as well as road, railway and waterway infrastructure since 2011 Chairman and co-owner of Büchting + Streit AG, Munich Editorial board member of peer-reviewed national / international journals such as 92

“Beton- und Stahlbetonbau” (Ernst & Sohn) and “Civil Engineering Design” (Wiley) Board member of the German Committee for Reinforced Concrete (DAfStB), ­member in a series of national and international standards committees and ­expert panels, e.g. DIN, EC, DIBt, fib Werner Lang Prof. Dr.-Ing. M. Arch. II (UCLA)

Born 1961 1982–1988 Studied architecture at ­Technical University of Munich (TUM) 1985/86 Studied abroad at the Architectural Association, London 1988 Diplom (Hans Döllgast Prize) at TUM 1988 –1990 Fulbright scholarship at ­University of California, Los Angeles (UCLA) 1990 M. Arch. II (UCLA), Award for Best Thesis at UCLA School of Architecture and Urban Planning 1990 –1994 Worked at Kurt Ackermann + Partner architectural consultancy, Munich since 1993 Member of the Bavarian Chamber of Architects 1994 – 2001 Research associate at the Chair of Building Technology Prof. Dr. Thomas Herzog, Faculty for Architecture, TUM 2000 Doctorate (Dr.-Ing.) at TUM, ­Doctoral Prize from the “Bund der ­Freunde der TUM” (Friends of TUM) 2001– 2006 Werner Lang architectural consultancy, Munich 2001– 2007 Lecturer for “Special aspects of facade construction” and “Building materials science” at the Department of Architecture, TUM 2006 Founder Lang Hugger Rampp GmbH Architekten, architectural con­ sultancy, Munich 2008 – 2010 Associate professor for Su­stainable Design and Construction at the University of Texas at Austin School

of Architecture (UTSoA) 2009 – 2010 Director of the Center for Sustainable Development at UTSoA since 2010 Holder of the Chair at the Institute of Energy Efficient and Sustainable Design and Building (ENPB) and Speaker of the Centre for Sustainable Building (ZNB), Department of Civil, Geo and Environmental Engineering TUM and Director of the Oskar von Miller Forum, Munich Stefan Winter Prof. Dr.-Ing.

Born 1959 1980 –1982 Carpenter training 1982 –1987 Studied civil engineering at Technical University of Munich (TUM) and Technical University of Darmstadt (TU Darmstadt) 1987–1990 Research associate at the Institute for Steel Construction and Mechanics of Materials and at the ­Institute for Concrete Construction at TU Darmstadt 1990 –1993 Director of the Institute of Carpenters, Darmstadt 1993 Founded engineering company bauart Konstruktions GmbH & Co. KG, with headquarters in Lauterbach and branches in Munich, Darmstadt and Berlin 1993 – 2003 Specialist consultant for the information service Informationsdienst Holz in Hesse 1998 Doctorate at TU Darmstadt, dissertation topic “Structural behaviour of steel concrete composite columns out of high tensile steel StE 460 under normal temperature and fire c ­ onditions” since 2000 publicly appointed sworn expert for timber construction at the Gießen-Friedberg Chamber of Industry and Commerce (IHK) 2000 – 2003 Chair of Steel and Timber Construction, University of Leipzig 2001– 2010 Partner at the materials

Appendix

research and testing body MFPA ­Leipzig GmbH since 2003 Full professor of Timber ­Structures and Building Construction at TUM since 2006 Certification engineer for structural engineering in the timber ­construction field in Bavaria 2009 – 2012 Finland Distinguished Professor (FiDiPro) at Aalto University, Helsinki since 2012 Chairman of the construction standards committee Department 04 “Timber Construction”, member of the DIN Standards Committee Building since 2014 Chairman of the European Standards Committee CEN TC 250 / ­SC 5 Eurocode 5 – Timber construction – Design and Execution Christina Meier-Dotzler Dipl.-Ing. (FH) M. Eng.

Born 1987 Dipl.-Ing. (FH) M. Eng. 2006 – 2010 Studied civil engineering, specialising in structural engineering, at OTH Regensburg (thesis on timber construction) 2010 – 2012 Master’s degree in civil ­engineering, specialising in building in existing contexts, at OTH Regensburg 2012 – 2013 Structural design engineer, BBI Ingenieure GmbH, Regensburg since 2014 Research associate for the Chair of Energy Efficient & Sustainable Design & Building, Technical University of Munich Joachim Hessinger Dipl.-Phys., Dr. rer. nat.

Born 1964 1983 –1992 Studied physics at Johannes Gutenberg University Mainz, graduated as Diplom-Physiker / Dr. rer. nat. 1993 –1995 Postdoctoral studies at ­Cornell University in Ithaca, New York since 1996 Working in the area of building acoustics at the Labor für Schall­

messtechnik (sound measurement laboratory), since 2003 LSW GmbH (sound and thermal measurement laboratory) / ­ift Schall­schutz­zentrum (ift Centre for Acoustics) / ift Labor Bauakustik (ift Building Acoustics Laboratory) in Stephans­kirchen / Rosenheim since 2005 Head of ift Testing Department Building Acoustics since 2005 Member of the DIBt expert committee SVA B2 “Sound insulation and sound insulation materials” since 2008 Member of DIN Standards Committee NA-005-55-74, AA DIN 4109 Christoph Kurzer M. Eng.

Born 1989 2011– 2016 Studied civil engineering at Beuth University of Applied Sciences, Berlin 2016 – 2018 Structural engineering project manager at consulting engineers EiSat GmbH, Berlin since 2018 Research associate for the Chair of Timber Structures and Building Construction at Technical University of Munich

since 2021 Associate Professor for Life Cycle Assessment and Material Use at NTNU in Trondheim Publications on the topics of life cycle analysis and sustainability in the design process Christof Volz Dr.-Ing.

Born 1982

2004 – 2009 Studied civil engineering at Technical University Munich (TUM) 2009 – 2016 Project engineer at engineering consultants ISP Scholz Beratende Ingenieure AG, Munich since 2016 Head of the bridges department at engineering consultants ­Haumann und Fuchs Ingenieure AG, Traunstein 2011– 2019 Visiting scholar at the Chair of Concrete Construction, TUM 2019 Doctorate at TUM: “The torsional stiffness of reinforced and prestressed concrete beams”

Patricia Schneider-Marin Dipl.-Ing. Architect

Born 1973 1993 – 2000 Studied architecture at ­Technical University Munich (TUM), EPF Lausanne and the University of Stuttgart 2000 – 2009 Worked at architectural consultants House and Robertson Architects, Coop Himmelb(l)au and Gehry Partners, Los Angeles 2009 Formed own architectural con­ sultancy in Munich 2010 – 2021 Research associate for the Chair of Energy Efficient & Sustainable Design & Building, TUM 2011 Co-founded ±e office for energy ­efficient building 93

Appendix

Image Credits

The authors and the publisher sincerely thank everyone who has contributed to the publication of this book through the provision of illustrations and artwork, granting permission to reproduce their documents or providing other information. All the drawings were specially produced for this publication, those in the project examples section on the basis of the architects’ drawings. Non-documented photos were taken from the architects’ archives or the archive of the journal Detail. Despite intensive endeavours, we have been unable to establish copyright ownership for some photos and illustrations. However, their claim to the copyright remains unaffected. In these cases, we ask to be notified. Title

Experimental residential buildings in Wuppertal-Ostersiepen (DE) 2012, ACMS Architekten Photo: Sigurd Steinprinz Photos introducing topics

Page 6: Neue Burse student hall of residence in Wuppertal (DE) 2013, ACMS Architekten Photo: Tomas Riehle Page 18: Building cooperative in Schwabing Nord. Residential building in Munich (DE) 2016, H2R Architekten Photo: Frank Kaltenbach Page 32: Cross section of timber panel element. “Ecoleben” – Multistorey residential building in Penzberg (DE) 2016, Lang Hugger Rampp Architekten and Krämmel Bauplan Photo: Christina Meier-Dotzler Page 48: Prefabricated wall element. “Am Mühlgrund” multigenerational housing in Vienna (AT) Hermann Czech, Adolf Krischanitz, Werner Neuwirth Photo: Rubner Holzbau GmbH Page 68: Experimental residential buildings in Wuppertal-Ostersiepen (DE) 2012, ACMS Architekten Photo: Sigurd Steinprinz Foreword

Huber & Sohn GmbH & Co. KG, ­Bachmehring Principles

1 – 5 Own illustration 6 a Sigurd Steinprinz 94

6 b Tomas Riehle 6 c Tomas Riehle 7 – 9 Own illustration 10 Sources: KfW standards: KfW, 2018; Passivhaus: Passive House Institute 2018; NZEB: EU, 2010; aktivplusHaus: aktiv-plus, 2018 12 In accordance with DIN EN 15 978:2012-10 13 Huber & Sohn GmbH & Co. KG 14 Own illustration using DIN 15 978:2012-10, DIN 15 804:2014-07 and Ökobaudat 15 Own illustration as per Brand, Stewart: How Buildings Learn. New York 1994 16 Own illustration as per Holzbau Deutschland – Bund Deutscher Zimmermeister im Zentralverband des Deutschen Baugewerbes e. V. (pub.): Lagebericht 2018. Berlin July 2018, Fig. 2.2 17 Own illustration as per Directive 2008/98/EC of the European Parliament and Council dated 19 November 2008 18 Own illustration as per manufacturer’s information Load-bearing structure and facade

1 Christina Meier-Dotzler 2 Own illustration as per Studiengemeinschaft Holzleimbau e. V. 3 – 5 Own illustration 6 Gumpp & Maier GmbH, Binswangen 7 Erne AG Holzbau, Photo: Gataric Fotografie 8 Own illustration as per StVO § 22 and Mette, Elmar: Transportieren und Montieren. Holzbau – quadriga 03/2014, p. 23 –27 9 Own illustration as per StVZO § 32 10 Hämmerle Spezialtransporte GmbH 11 Own illustration as per StVZO § 32 12 –14 Own illustration 15 As per DIN EN 13 670:2011-03 16 As per DIN 18 202-3:2008-08, Tab. 2 17 After DAfStb-Heft, issue 631: Hilfs­ mittel zur Schnittgrößenermittlung und zu besonderen Detailnachweisen bei Stahlbetontragwerken; Chapter 4. Based on DIN EN 1992 18 As per DIN EN 1992-1-1 19 –23 Own illustration 24 Hilti Deutschland AG, except fig. centre: Unternehmensgruppe ­fischer

Building physics

1 Own illustration as per EnEV 2 – 6 Own illustration 7 Christina Meier-Dotzler 8 Own illustration 9 Christina Meier-Dotzler 10 –12 Own illustration as per MBO 13 bauart Konstruktions GmbH & Co. KG 14 Huber & Sohn GmbH & Co. KG, Bachmehring 15 Own illustration 16 In accordance with Merk, Michael; Werther, Norman; Gräfe, Martin: Erarbeitung weiterführender Konstruktionsdetails für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4, Abschlussbericht des Lehrstuhls für Holzbau und Baukonstruktion at Tech­nical University Munich, Forschungsinitiative Zukunft Bau, Volume F 2923. Stuttgart 2014 17 –18 Own illustration 19 Own illustration taking into account DIN 4109 and VDI 4100 20 –25 Own illustration 26 Christina Meier-Dotzler External wall joints

1– 2 Own illustration 3 Own illustration according to information from Gumpp & Maier GmbH, Binswangen 4 Own illustration 5 Own illustration as per MBO Example projects

Page 70 – 73: Constantin Meyer ­Photographie Page 75: HHS Planer + Architekten Page 76 – 79: Sigurd Steinprinz Page 80: ACMS Architekten Page 81: Sigurd Steinprinz Page 82 – 83: Krämmel Unternehmensgruppe, Wolfratshausen. Photo: Alexander Bernhard Page 84: Christina Meier-Dotzler Page 86 – 89: Florian Holzherr Page 90 – 91: Gumpp & Maier GmbH, Binswangen

Appendix

Standards

Acknowledgments

DIN 18 202 Tolerances in building construction – Buildings DIN 18 203 Tolerances in building construction – Part 3: Building components of wood and derived timber products DIN 4102 Fire behaviour of building ­materials and building components DIN 4108 Thermal protection and energy economy in building DIN 4109 Sound insulation in buildings DIN 18 540 Sealing of exterior wall joints in building using joint sealants – com­ parable with DIN EN 15 651-1 Sealants for non-structural use in joints in buildings and pedestrian walkways – Part 1: Sealants for facade elements, but additional requirements are placed on joint sealants in this standard that are not included in DIN EN 15 651-1 DIN 18 533 Waterproofing of elements in contact with soil DIN 18 531 Waterproofing of roofs, bal­ conies and walkways DIN 68 800 Wood preservation DIN EN 13 162 Thermal insulation products for buildings – Factory made mineral wool (MW) products – Specification DIN EN 15 651-1 Sealants for non-­ structural use in joints in buildings and pedestrian walkways – Part 1: Sealants for facade elements

This publication is based on the results of the research project “Fassadenelemente für Hybridbauweisen” (Facade elements for hybrid construction), Technical University Munich, 2014 –2016 (hybridbauweisen.de) The project and publication were funded by the Bavarian construction industry.

Particular thanks go to: employees Miriam Kleinhenz and René Stein, • student assistants Pierre Keller-Psathopoulos, Jochen Mecus and Christoph Werner, and • construction practice partners at the companies ift Rosenheim GmbH, Gumpp & Maier GmbH, Huber & Sohn GmbH & Co. KG, bauart Konstruktions GmbH & Co. KG, ZÜBLIN Timber ­Aichach GmbH, Krämmel Unternehmensgruppe and ACMS Architekten • former

95

Appendix

Subject Index

A Access balcony  49f., 56f., 86f. Accessibility  49, 57 Acidification potential  15 Airborne sound  42ff., 46 Airtightness  8, 36f., 51 Aktivhaus  12, 70ff. Anchor bolts  30, 49ff. Annual heating energy demand  12 Assembly sequence  49ff. B Base  35, 49, 58f., 60f. Beams49 BNB (Assessment System   or Sustainable Building)  12ff. Building class  7, 38ff., 51ff. Building cost indices  16f. Building stiffness  7f., 20ff. Butt joint  22, 38, 43, 52ff., 64

 Thermal insulation composite system (ETICS)  8f., 15ff., 34ff., 37ff., 45f., 64   ventilated  8f., 51ff. Fire protection  37ff., 49ff.   requirements  37   concept  37f., 64f. Fire-resistance rating  51ff., 37ff., 65 Fire stops  40 Firewall / firewall replacement wall 38, 64ff. Flanking sound transmission 51ff., 42ff., 64 Floor slab  7ff., 28ff., 35, 37, 41, 49ff. Formwork  21 G Glued laminated timber  Greenhouse gas potential  H Horizontal tensile forces 

20, 50 11ff.

50

C Centre-to-centre distances  28 Condensation  36 Connections  9f., 19f., 28ff., 49ff. Core element  8f., 15f. 20, 36ff. 49ff. Costs 9, 16f., 23ff. Crosswall construction  7f. Curtain wall  8, 17, 49ff., 65

I Impact sound  41f., 51ff. Installation costs  16f. Installation joints 43f., 46f. Installation phase  9ff., 22ff., 43f., 49ff. Insulation standard (thermal)  8, 11ff.,  33f., 49 Interface  26f.

D Dead load  7ff., 28 Deformation  19, 21, 26ff., 49ff. Design for disassembly  11, 14 DGNB (German Sustainable Building  Council) 12ff. Diffusion tightness  36 Dimensional tolerance  26ff. Dismantling  12f.

J Joist  Joint

E Economic efficiency  16ff., 19 Economy  16ff. Effizienzhaus12 End-of-life scenarios  15f. Energy efficiency  11ff., 33 Energy Saving Ordinance   (EnEV)  11f., 33f. European Technical Assessment – ETA  8, 30, 50 Eutrophication potential  15

M Manufacturing tolerances  22, 26ff., 49 MBO (Model Building Code)  37ff., 65 Mineral wool  17, 39ff. Moisture protection  36ff., 49ff.

F Facade   rear-ventilated 

96

8f., 15, 35ff., 46, 51ff.

49f. 9, 11, 22, 48ff., 64ff.

L Life cycle  Life cycle analysis  Life cycle assessment (LCA)  Laminated veneer lumber 

N Nearly zero energy building   (NZEB) 

11ff. 12ff. 13 50

P Parametric study  Passivhaus  Photochemical ozone creation   potential  Point supports  Primary energy 

O Ökobaudat  13f. OSB (Oriented strand board)  15, 22, 37,  40, 49ff. Ozone depletion potential  15

15 7 11ff., 33

R Recycling  12, 14ff.   concepts  14  potential 13 Reference building  12, 33 Render carrier board  49ff. Resource depletion potential  15 Reuse  11ff., 16 Road Traffic Regulations (StVO)  23 S Services cavity  8f., 17, 46, 49, 52ff. Skeleton frame  7f. Solid structural timber (KVH) 20, 49ff. Sound insulation  8f., 41ff., 49, 51ff., 65 Splash water zone  49, 58, 60 Stiffness  7f., 27f. Structural design  19ff. Sustainability  11ff. System boundary  13f. T Thermal bridge  9, 12f., 33ff., 49, 51ff. Thermal insulation  8f., 11f., 33ff., 49, 51ff. Thermal transmittance  33f. Timber panel construction element  7ff.,  11f., 20ff., 28, 33ff., 39f, 49ff.   inserted 9f., 25, 28, 35, 37, 43ff., 49, 54   self-supporting  8f., 20f., 25, 35ff., 44ff.   suspended  9f., 28, 35, 44f. Tolerances  9ff., 22, 26ff., 37, 49 Transmission heat loss  12, 33f. Transport  13, 22ff. U U-value  V Vertical loads 

12

27ff. 12

11ff., 17, 35, 49, 51, 65

20, 27, 29, 49f.

W Wall elements 45 Wind loads  7ff., 20, 28, 49, 64 Windtightness  8, 37ff., 64 Wood fibreboard  45 Wood preservation  51 Wood-based material  8, 20, 36, 39f.