COST C16 Improving the Quality of Existing Urban Building Envelopes IV: Facades and Roofs (Research in Architectural Engineering)

COST C16

Improving the Quality of Existing Urban Building Envelopes

FACADES AND ROOFS

Research in Architectural Engineering Series Volume 5 ISSN 1873-6033 Previously published in this series: Volume 4. R. di Giulio, Z. Bozinovski and L.G.W. Verhoef (Eds.) COST C16 Improving the Quality of Existing Urban Building Envelopes – Structures Volume 3. E. Melgaard, G. Hadjimichael, M. Almeida and L.G.W. Verhoef (Eds.) COST C16 Improving the Quality of Existing Urban Building Envelopes – Needs Volume 2. M.T. Andeweg, S. Brunoro and L.G.W. Verhoef (Eds.) COST C16 Improving the Quality of Existing Urban Building Envelopes – State of the Art Volume 1. M. Crisinel, M. Eekhout, M. Haldimann and R. Visser (Eds.) EU COST C13 Glass and Interactive Building Envelopes – Final Report

COST C16

Improving the Quality of Existing Urban Building Envelopes

FACADES AND ROOFS

edited by: Luís Bragança Christian Wetzel Vincent Buhagiar Leo G.W. Verhoef

IOS Press

© 2007 IOS Press and the Authors. All rights reserved ISBN 978-1-58603-737-6 Published by IOS Press under the imprint Delft University Press Publisher IOS Press BV Nieuwe Hemweg 6b 1013 BG Amsterdam The Netherlands tel: +31-20-688 3355 fax: +31-20-687 0019 e-mail: [email protected] www.iospress.nl www.dupress.nl LEGAL NOTICE The publisher is not responsible for the use which might be made of the following information PRINTED IN THE NETHERLANDS

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Table of Contents Preface L.G.W. Verhoef

vii

Introduction V. Buhagiar

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Summary V. Buhagiar

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Country Contribution Papers Technical Improvement of Housing Envelopes in Cyprus P. Lapithis, Ch. Efstathiades, G. Hadjimichael

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Technical Improvement of Housing Envelopes in Denmark T. Dahl, E. Melgaard, J. Engelmark

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Technical Improvement of Housing Envelopes in France D. Groleau, F. Allard, G. Guarracino, B. Peuportier,

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Technical Improvement of Housing Envelopes in Germany Ch. Wetzel, F.U. Vogdt

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Technical Improvement of Housing Envelopes in Hungary A. Zöld, T. Csoknyai

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Technical Improvement of Housing Envelopes in Italy S. Brunoro

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Technical Improvement of Housing Envelopes in the F.Y.R. of Macedonia S. Trpevski

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Technical Improvement of Housing Envelopes in Malta V. Buhagiar

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Technical Improvement of Housing Envelopes in Poland Z. Plewako, A. Kozáowski, A. Rybka

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Technical Improvement of Housing Envelopes in Portugal L. Bragança, M. Almeida, R. Mateus

115

Technical Improvement of Housing Envelopes in Slovenia M. Sijanec Zavrl, J. Selih, R. Zarnic

127

Technical Improvement of Housing Envelopes in The Netherlands Ch. M. Ravesloot

139

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Comparison of Design Criteria Comparison of Design Criteria Ch. Wetzel

153

Annex COST C16 Management Committee

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COST C16 Working Group Members

171

vii

Preface

In front of you lies one of the four books produced within the scope of Action C16 “Improving the quality of existing urban building envelopes” which started as a COST UCE programme. The acronym ‘COST’ stands for European COoperation in the field of Scientific and Technical research, and falls under the Urban Civil Engineering Technical Committee (UCE). The main characteristic of COST is a ‘bottom-up approach’. The idea and subject of a COST Action comes from the European scientists themselves. Participation is open to all COST countries but only those countries that wish to participate in an Action do so. As a precursor to advanced multidisciplinary research, COST has a very important role in building the European Research area (ERA), anticipating and complementing the activities of the Framework Programmes, acting as a bridge between the scientific communities of emerging countries, increasing the mobility of researchers across Europe and fostering the establishment of large Framework Programme projects in many key scientific domains. It covers both basic and applied or technological research and also addresses issues of a pre-normative nature or of societal importance. The organisation of COST reflects its inter-governmental nature. Key decisions are taken at Ministerial conferences and also delegated to the Committee of Senior Officials (CSO), which is charged with the oversight and strategic development of COST. The COST Action C16 “Improving the quality of existing urban building envelopes” is directed to multi-storey residential blocks from the period after World War II, especially those built during the period when the need for housing in Europe was at its greatest. That is why the COST Action C16 focussed on the period 1950 to 1980. We found it necessary to propose this Action after the completion of Action C5 “Urban heritage/building maintenance”. According to studies carried out by Action COST C-5, the estimated value of the European Urban Heritage amounts to about 40 trillion Euro (1998 prices) for the housing stock alone. The same research indicated the differences between the countries of the EU as well as what they have in common. The age profile of the building stock of a country like the Netherlands differs from that of the UK. Of interest too, are the costs of maintenance, renovation and refurbishment of the building stock. For the EU as a whole, this amount is about 1 trillion Euros per year (1998 prices). At the same time the three ‘Building Decay Surveys’ issued by the Federal Government of Germany that were based on systematic, scientific building research projects, indicated that 80% of all building decay is found in urban building envelopes (roof, walls, foundation). There are elements in the building stock that are common to the countries in Europe. These include:  Most of the buildings were completed after 1950. For a country like the Netherlands this means 75% of the existing buildings.  The maintenance costs are mainly incurred in urban building envelopes,  The renovation of buildings and reconstruction to provide an improved or different range of use will influence the building envelope,  The quality of the building envelope very often fails to meet current demands and will certainly not meet future demands.

viii An important conclusion deriving from the points mentioned above is that however important maintenance may be, it does not lead to the desired improvement in the quality of urban building envelopes. Improvement of the quality of urban building envelopes must be the real task. Such improvement requires the development of new and suitable strategies for local authorities, housing corporations and owners and also architects and civil engineers. Until now integrated engineering aspects have been disregarded in this process. In many European countries new technologies have been developed, but these have either not yet been translated into practice, or have been only locally used to achieve a higher quality in urban buildings. This results in a limited impact on urban environments. Therefore it is essential to bring all kinds of local solutions together, to learn from these and to find a more general approach that can be used for building systems. Often problems and their solutions are approached in isolation. The wish to improve the quality of an individual building envelope usually leads to a local, project-based solution. Solving the specific problems of this renovation-project becomes the sole target. To reach maximum value for money, it is essential to integrate all the factors influencing urban building envelopes and look at them in a broader scope. As a result of changes in the composition of the population, society continuously changes with respect to various factors including age-structure, family composition and the availability of energy. Changes lead to situations that are reflected in the commissioning of buildings, which is gradually shifting from new construction to the reuse and renovation of existing buildings that often requires the modification of their facades. Even when buildings may still be functionally satisfactory, there may be external factors, such as the dullness of the image that they summon up or their poor technical quality, that require that attention should be paid to the shell of the building. There are many reasons why buildings may no longer be adequate. Failure to satisfy current demands may be expressed in lack of occupancy and further deterioration of the neighbourhood. This establishes a vicious circle, which can and must be broken. All too quickly discussions turn to demolition and new development, without prior investigation of the reasons for the situation. From an economic point of view, renovation and the reuse of buildings, which takes into consideration the technical and spatial functions and also the urban and architectural aspects, often appears to provide a better solution. The aim of the COST Action C16 is to improve techniques and methods used to adapt the envelopes of buildings constructed during the second half of the 20th century in the COST countries. These ‘non-traditional buildings' were constructed from in situ poured concrete systems, large scale prefabricated systems and/or small concrete/mixed elements although in some countries brick or stone was still used. The demand for housing in the post-war period necessitated the rapid production of large numbers of dwellings. Qualitative aspects were less important. Furthermore dwellings of the types constructed at that time no longer fulfil contemporary or anticipated future demands for housing, with the possible exception only of those built during the last 5 years. At this stage, it must be noted that two other ongoing Actions in the field of Urban Civil Engineering, also address issues related to buildings: COST Action C12 on “Improving buildings’ structural quality by new technologies”; and COST Action C13 on “Glass and interactive building envelopes”. The Technical Committee on Urban Civil Engineering considers that in addition to the tasks directly connected to the main objective of their Action, participants in the COST Action on “Improving the quality of existing urban building envelopes” should establish and maintain close contacts with the two above mentioned Actions. This will foster co-operation with these Actions and avoid potential overlaps. About one year after the start of COST Action C16, it was put on a hold for more than 8 months, to permit the ‘renaissance’ of the COST programmes, while in the meantime COST C12 had almost ended and it was considered that the C13 Action had only a slight connection

ix with the targets of COST C16. The CSO therefore agreed with the request of the Management Committee that the end of this Action should also be postponed by 8 months so that it would still last for the planned duration of four years. SCIENTIFIC PROGRAMME To date problems relating “Urban Building Envelopes” and their solutions are approached in isolation. The original design planners, architects and engineers work together to realise a building according the current state of knowledge, but this co-operation longer exists during the lifecycle of the building. For far too long prolongation of the occupation by the use of maintenance was sole aim. If improvement did become an option only a few aspects were considered. At present the current state of knowledge is usually local, being concentrated in some of the housing co-operations, architectural and engineering companies. However much has been done to spread this information in order to initiate discussion about when and how existing buildings with their envelopes can be improved to fit them for the future. The COST mechanism will foster international concentration on the integrated problems related to non-traditional dwellings. It will create a direction for improvement of urban building envelopes and also illustrate the state of the art in the various countries concerned.. What has already been learned in one country can now easily be shared or can be translated to fit the needs of other countries. His will make the implementation of new practices much easier. The World Wide Web will be used to bring all the information on the major non-traditional housing systems in Europe together as well as the various techniques for the improvement of urban building envelopes. We are happy to announce that for the first time since the establishment COST, it has become possible not only to publish books but to place the information on the World Wide Web. See www.costc16.org. High schools and universities interested in the subject of the renovation of existing buildings can now have east access to this knowledge. This study was based on the following scientific programme:  Description and analysis of the types of system related to the factors influencing urban building envelopes;  Analysis and comparison of the legislation and technical regulations relating to renovation in European countries;  Analysis of how urban building envelopes have been changed to date in relation to relevant factors;  A survey of existing engineering techniques that can be used, modified or developed to reach this goal;  A synthesis of possible global approaches leading to guidelines on how to reach maximum value for money in relation to the desired quality and working conditions in the urban environment and also how this approach can be reached for other types of buildings. THE SCHEME OF THE APPROACH OF ACTION C16 The original idea given in the technical annex of the Action was to start with a preliminary approach lasting six months. After that, three working groups would be set up on the themes of: the current envelopes, the needs and the techniques. A period of three years was allocated for this. The last six months of this period would have been used to integrate the result of the working groups and to prepare the final international symposium. As stated above, one year after the start of the Action C16, together with other Actions, was placed on hold, because of the reorganisation of the COST organisation to create an umbrella organisation. At the beginning of 2004, on the basis of the contract between the European Science Foundation and the European Commission for the Support of COST, this reorganisation started with the establishment of the fully operative COST office in Brussels.

x This delay caused to loss of some momentum. A second problem that had to be solved was that the members of C16 came from a variety disciplines and included structural engineers, architects and physicians. Although an interdisciplinary approach is one of the targets of a COST Action, this did give rise to problems in the working group on techniques. For example bearing structures demand a different specialisation from that required for secondary elements, such as facades and roofs. The management committee was wise in its decision to split the Techniques Working Group into a working group on structures and a working group on facades and roofs. THE METHODOLOGY The methodology used for the work of the four working groups of the Action C16 “Improving the quality of existing urban building envelopes” differs. The first book entitled ‘The state of the art’ is divided into two parts. The first part comprises a survey on the housing stock for each country. It contains data related to the building period, main typology and technologies. In the second part the topics covered describe the quality of the housing stock. The ‘state of the art’ depends on the time at which a survey takes place. That is why we consider it an advantage to also publish the two keynote lectures in this first book. These describe approaches to the modification of the multi storey family stock that is currently under investigation. In the second book, ‘The needs’, the method used to obtain precise information was to develop a table that includes the needs, solutions and priorities for each country. It is evident that these needs and priorities will differ greatly from country to country, as illustrated for example by comparing Sweden to Malta. To determine these aspects, criteria such as land use, architectural aspects and building physics are used, as well as aspects relating to finance and management. In the third book, ‘Structures’, a framework for possible solutions has been set up. It contains 20 case studies in which changes in bearing structures to fit for future purposes was the goal. Examples include descriptions of how to build extra floors onto existing buildings for both financial reasons and also to make the installation of elevators more profitable.. Another example illustrates the need for greater flexibility, and shows how a part of the bearing structure can be changed to provide this. In the fourth book, ‘Facades and roofs’, which is based on the results of the working groups’ The state of the art’ and ‘Needs’, two documents have been developed, ‘Technical Improvement of housing Envelopes’ and ‘Country Criteria in the form of a matrix’. Relations between the most frequently used refurbishing solutions and their impact on sustainability have been worked out in depth. Sustainability is described in a set of performances such as, technical, economic, functional/social and environmental. Case studies illustrate these theories. Together these books provide much information and can help countries and people to learn from each other. It is my wish that that you will all profit from their content. Leo G.W. Verhoef (Chairman COST Action C16) April 2007

Introduction V. Buhagiar Faculty of Architecture and Civil Engineering, University of Malta, Malta.

The main goal of the Working Group 3B (WG3B) of the COST Action C16 was to study the different technical possibilities to retrofit the functional requirements of the multi-storey housing building envelopes of European buildings built after the II World War. This work is based on the State-of-the-Art documents and on the needs of such buildings that were identified by Working Group 2. For the output of the WG3B was possible to gather the contribution of 14 different European countries: Cyprus, Denmark, France, Germany, Greece, Hungary, Italy, Macedonia, Malta, The Netherlands, Poland, Portugal, Slovenia and Sweden. The output of the scientific work that was carried out by each participant country on the context of this working group is set through two types of documents, organized in two Chapters:  Technical Improvement of Housing Envelopes and Country;  Comparison of Design Criteria. In order to facilitate the comparison between countries and the interpretation of data, a format for each type of document was created to guide the authors. The contributions from all EU member states represented in this workgroup, numbering eleven countries, are now complied. Each paper describes the different aspects of an exterior refurbishment in the respective country, under a standard list of headings, namely the technical, functional, social performance, economical performance and the environmental performance of the building after a façade or roof retrofit. It is worth highlighting that this COST C16 action was not based on a research-funded initiative and hence no pure research was carried out. However members to all workgroups were experienced hands-on practitioners, bringing in their own ‘baggage’ of knowledge through private research and a wealth of experience in the respective fields of architecture, engineering or building physics, thus enriching the workgroups through dissemination of knowledge. It was for this reason that a screening process is typically carried out for the selection of national delegates, through the respective country’s COST Office and scientific officers. The papers are the fruit of all this. Although some papers may be describing practical standard methods for technical improvements in the building envelope, these are by no means to be considered as prescriptive for a quick-fix solution, as every case needs to be studied separately on its own merit. Further details on each paper may be obtained through direct contact with the author, whose details may be retrieved from the cost web site, under the respective workgroup or Institution. The aim of Chapter “Technical Improvement of Housing Envelopes” is to present the main problems in multi-storey building envelopes of each country and to present the main technical solutions that are being adopted to overcome those problems. The format consists in four parts:  In the first part the most relevant problems in the envelopes and the most used retrofitting solutions are identified;

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Introduction

 

The second part resumes the technical specifications of the most used refurbishing solution; In the third part the document presents the impact of the most used refurbishing solution on the sustainability topics. The sustainability topics are divided in technical performance, economic performance, functional/social performance and environmental performance; At the end, each document presents a case study about a real example related to the adoption of the refurbishing solution that was presented.



The impact of the most commonly used refurbishment actions was studied under the point of view of the several aspects of the envelope performance as follows:  Technical performance - stability, capacity, earthquake resistance, fire protection, noise insulation, weather protection, moisture protection, conductivity, heat flow, radiation, convection and durability (service life);  Functional and social performance - flexibility, comfort (thermal, acoustical, visual), health (air quality, VOCs, mould & fungus growth), safety, barrier free, etc.;  Economical performance - building costs and running costs (heat losses, cooling, cleaning, inspection, maintenance, etc.);  Environmental performance - use of resources (non renewable, renewable), energy consumption for heating/cooling (non renewable, renewable), environmental impacts (global warming potential, acidification potential, nitrification potential, eutrophication potential, ozone depleting potential, photochemical ozone creation) and waste. In spite of the differences found between countries, the analysis of the documents shows that one of the most used solutions to refurbish the multi-storey housing European buildings is to coat the existing façades with an external thermal insulation composite system (ETICS). Comparing the different documents it is possible to identify and compare the technical differences and the impact on the sustainable topics of the different solutions. The aim of Chapter “Comparison of Design Criteria” is to compare the design criteria used in each participating country. For that purpose a Country Criteria Matrix was established on the basis of a survey carried out in each country. The Country Criteria Matrix is a table that summarizes the actual thermal requirements and some proprieties of the current building envelopes (façades and roofs). The comparison of the design criteria is organized in four parts:  The first part starts with a survey on the climate and on the thermal requirements of each country’s legislation;  The second part reports about the current solutions found in the façades of the buildings and the most used solutions used to refurbish it;  The third part deals with the same issues as the second part but for roofs;  The comparison ends with a survey about the adoption of the new European Energy Performance of Buildings Directive in the participating countries. From the analysis of the results interesting salient features were highlighted and it is also possible to verify that not all aspects could be applied to every country and some aspects were interpreted differently. Another relevant aspect is that there are huge differences between the current technical solutions observed in the participant countries, mainly between those that were and were not involved on the II World War and between Mediterranean and Northern countries. Finally, and as concluding remarks, WG3B was an excellent forum of exchanges between experts in separate disciplines which complement each other in the integration of technologies for the improvement of envelopes in view of higher living quality in urban environment. The results achieved can have direct positive impact on the environment through the savings on material and energy consumption and the possibilities for dismantling and recycling. Expertise on each of WG3B topics exists in all European countries, but until now no integrated knowledge was available. In this context the COST scheme was the ideal platform to gather a multidisciplinary team to integrate new technologies in the field of the renovation of urban buildings envelopes and to disseminate understanding and knowledge.

Summary V. Buhagiar Faculty of Architecture and Civil Engineering, University of Malta, Malta.

In post-war Europe, the main thrust behind residential building projects was for every country to provide social low-rent housing in most job-depressed cities. This was every government’s moral obligation. This building activity brought with it the fast track, low-cost pre-fabricated concrete structures and loose masonry or composite steel construction, all oblivious to upcoming social needs, rapid advances in construction technology and the importance of energy efficiency in buildings. Since the 1950s and 1960s such problems had not yet emerged. However with the onset of the energy crisis in the 1970s a greater energy consciousness emerged, not for environmental motives but moreover for diminishing the added financial burden for social low to middle income earners. Between 1980 and 2000 a wave of refurbishment projects went through Europe, especially with the enlargement of the European Union, which saw an increase from 15 to 27 member states (2007), thus increasing the importance of energy conservation in a more sustainable unified approach, through quasi-streamlined solutions and legislation. This prompted the need for a concerted awareness of common problems, through a state of the art assessment, prompting needs and the ensuing structural and environmental solutions towards this goal. This C16 COST action purports to achieve just that. Through its four workgroups, these four books are the product of its work package output, over four years. Although not a research based action, COST C16 pulls together a whole baggage of experience and individual research initiatives of each member put together in these four volumes. The fourth workgroup, namely 3B, sums up the possible technical solutions for an energy conscious, cost-sensitive refurbishment of the urban building envelope. Today this encompasses both private and social housing, on both a minor and major scale. Solutions vary from innovative technological solutions, or the now established ETICS (exterior thermal insulation composite systems) to simple projections and attic insulation. Solutions vary from country to country across the enlarged European Union. It is perhaps in the spirit of this union that these solutions needed to be brought together in this book, one of four in the series, summing up the end product of four years’ hard work of the C16 COST action. This fourth and last book is perhaps the first ever collated set of technical solutions in one volume. An overview summary of each chapter, country by country is now given. COUNTRY CONTRIBUTION PAPERS Cyprus This contribution highlights the main problems associated with the building envelopes in Cyprus and current standards applicable for existing buildings. Since most buildings in Cyprus are constructed with little or no insulation, this results in a greater summer and winter discomfort, attracting the associated energy demands for cooling and heating respectively. A description of the most commonly used refurbishment options for standard envelopes are tabulated and discussed, followed by multi-faceted recommendations for the technical, functional, social, eco-

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nomical and environmental aspects of existing building stock. Finally application methods are described through two different case studies, one on an existing energy efficient refurbishment and another highlighting the potential for energy efficiency through passive solar architectural design. Denmark The increasing demand for energy conservation, decay of building materials, alternative methods of façade construction, leaking roofs and water penetrating vertical cladding have all prodded the need for major refurbishment jobs to post-war housing stock in Denmark, as highlighted in this contribution. The Danish way of renovating is however multifaceted. There is not a single or a general method or technology. The original external walls can be divided in three different types of construction: traditional masonry cavity walls, the industrialised concrete sandwich wall and the lightweight wooden façade system with plates or boards of wood, fibrecement or any other materials used as cladding. The general problems are most significant for the non-traditional built external walls, and they are most commonly renovated by adding an external secondary lightweight construction with extra insulation and new cladding, which might be with or without ventilation behind. The paper gives a general description of the performance of such systems illustrated through two case studies demonstrating renovation of sandwich and lightweight constructions respectively. France The country’s paper highlights the fact that the improvement of housing envelopes can play

an important role to change the image of such a building with its users and external environment. Internally, these same blocks are also changed with such a refurbishment exercise. With all this in perspective, since 1980 in France, rehabilitation of façades has been one of the predominant measures applied to externally modify the image of the building without disturbing tenants’ lifestyle. Aesthetics apart, from a technical aspect, the main technique used consists of applying an external modern skin to the existing façade, including thermal insulation. This naturally offers numerous technical and functional advantages over existing cladding or load bearing wall systems. Such changes however do not come without side-effects: an increase in indoor temperatures was noted, as well as a change in habitat and use of spaces by tenants. Although occupants are first sceptical about such retrofitting, the paper highlights the importance of involving all stakeholders from day one, namely building consultants, municipalities and residents, highlighting that the effects of such changes will only be felt over a period of time. The true success of a retrofitting operation is strongly dependant on the quality level of implementation and degree of acceptance of each project. Germany The paper outlines the motive behind energy efficient refurbishment of façades in Germany: this was sparked off by the first ever legislation for energy efficient construction in 1985. This specified stringent heating insulation requirements for new buildings (circa 88 % of today’s stock) while the remaining12% of existing stock were considered as having ‘sufficient’ insulation levels. However if a refurbishment job is undertaken, and if more than 25% of the existing cladding of the building façade has to be removed, then the whole new façade had to reach a U-value lower than 0.4 W/m²K. This brought about the need for ETICS (External Thermal Insulation Composite Systems), where out of this necessity a thick layer of around 12-15cm insulation was needed to reach this U-value. The paper deals with a novel way of recycling and re-use of such insulation materials for a different type of ETICS.

Summary

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Hungary Considering that heating energy consumption stands at 150-220 kWh/m2year, the thermal performance of post-war social housing stock is unacceptable by today’s standards. This is attributed to the post-war need for rapid speed of construction, use of prefabrication elements and poor detailing culminating in today’s energy wastage. Moreover in early post-war days (194050s) energy costs were only 1% of today’s figures. The principal problems found in early social housing in Hungary are associated with poor thermal performance: thermal bridges, bad whether proofing and lack of air-tightness combined with related fabric damages. This resulted in high operational costs and a low standard of living. Uncontrollable heating systems increased energy wastage. Although several implemented initiatives were not so successful in the last decade due to false pretexts on payback periods, today successful demonstration projects prove the energy saving potential from such retrofits. This is demonstrated through a quality case study. Italy The main problems associated with Italian building envelopes are the lack of thermal and acoustic insulation and the poor quality of the windows (single-glazed windows and window frames with low air-tightness). The lack of performance and the consequent inability to make use of the climatic resources cause a high level of heat loss in winter and overheating in summer. The use of a ventilated façade in the refurbishment and upgrading of existing buildings is recommended in a wide variety of scenarios. The procedure must be carefully designed and planned in order to evaluate which will be the most appropriate and successful solution. Examples of ETICS and novel construction materials – through detailed case studies – demonstrate that a specific design, relating in particular to the individual situation can be beneficial to both the technical and architectural quality of the building with reasonable costs and positive environmental effects. F.Y.R. of Macedonia Buildings consume a large slice of the energy consumption of Macedonia, as elsewhere. The paper highlights the potential for energy savings in the residential and tertiary sectors. Given the low turn-over rate of buildings (lifetime of 50 to more than 100 years) it is clear that the largest impact for improving energy performance in the short and medium term is in the existing building stock. Major renovations of existing buildings (above a certain size) are regarded as an opportunity to take cost effective measures to enhance energy performance by meeting minimum energy performance standards tailored to the local climate. Over the past 20-25 years, in many cases standards have been reinforced two to four times, including some very recent revisions. Towards this aim, for façade refurbishment, the most appropriate technical solution is selected called “Externally Insulated Façade System”- EIFS (similar to ETICS). An important case study in Skopje manifests its application. Malta The principal problem of residential building envelopes in post-war Malta is that there was never a deliberate effort to use insulation in cavity walls, be it for thermal or acoustic performance. However there was always a concern for moisture isolation by the use of cavity walls against rain penetrating the external porous limestone skin and using a damproof course to isolate the lower damp foundations from the rest of the building. In all fairness there is no real extensively designed façade refurbishment in Malta, which is purposely designed for energy efficiency, particularly in the housing sector. As from 2007, with the introduction of the new building regulations (part F), the enforceable legislation has made it mandatory for walls and flat roofs to reach a certain U-value, albeit even if still considered lenient. In government housing projects there have never been any new energy conscious design or refurbishments to social housing blocks, except for one new project in Birkirkara, a first of its kind for Malta, executed in 2005 by the author.

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Summary

Poland The idea of External Thermal Insulating Dry System (ETIDS) consists of adding insulation sheets to an existing façade, covered by an external cladding panel, supported with a structural frame, and fixing it to original wall structure. Although the system was developed as an original idea, it was based on commonly available materials. It was especially dedicated to improve the thermal insulation of pre-cast external walls in large panel building technologies – the most popular technology of multi dwelling building in Poland. This paper presents one of the first popular technologies widely used in Poland for upgrading the thermal resistance of façades in multi-family housing buildings, made with the use of a non-traditional technology. As a reaction to more strict control over energy consumption, it became popular in the 1980s due to its material and technological simplicity resulting in relatively low construction costs. Description of this system contains basic data of system elements, installing technology, details and performance with pointed out impact of the refurbishment action with ETIDS system on sustainability topics. Specification of ETIDS is complemented with examples of typical applications. Portugal The paper highlights the main problems in multi-storey post-war building envelopes, namely the low thermal insulation and low airborne sound insulation. Today the most used refurbishing solutions for vertical envelopes are: the External Thermal Insulation Composite Systems (ETICS), the Ventilated Façades and the replacement of existing windows by double glazed and low air permeability ones. In this paper, the potential of the ventilated façade as a refurbishing solution, mainly for buildings built after the 70’s, is assessed. Façades built in this period do not fulfil actual users’ comfort standards and construction codes. It was therefore necessary to find the most appropriate technical solutions to refurbish such façades. This paper evaluates the impacts of this technical solution in standard envelopes, analysing the data available, and compares it with data from other technical solutions, weighting the different dimensions according to local constrains and the objectives of the project. The paper also highlights the possibility to evaluate the sustainability of the ventilated façade as a solution to improve conventional façades. Slovenia: The social housing stock built between 1946-1970 had no thermal insulation, possibly with double glazed box windows, but since the 1970s early thermal insulation materials were introduced. Nowadays, these buildings offer significant energy saving potential and often need repair because of inadequate maintenance. Since Slovenia is an earthquake prone zone interventions in envelopes in many cases comprise also additional strengthening of the structure. Recently (2002), national legislation imposed some obligatory measures on envelope refurbishment, which are however supported by subsidies for energy efficiency. Although there are different technical solutions for envelope insulation improvement, the most frequently applied is the external thermal insulation system where a thin layer of plaster is used, accompanied with multi-chamber PVC windows with low-e double glazing. The durability of a thin layer plaster ETICS may not be as high as in case of ventilated insulation system, but this limitation can be compensated with far lower investment costs. To overcome the general financial barriers for renovation of building envelopes for major renovation, State subsidies are made available, if specific energy efficiency targets are met. A well-detailed recent case study reflects today’s correct contemporary approach toward such a refurbishment. The Netherlands This final contribution identifies typical problems in post-war building stock as being the lack of thermal comfort, loss of functionality of the floor plan and social deterioration of the neighbourhood. Changes of the dwellings in such housing complexes include energy saving measures, alteration of the floor plan functionality in more differentiated housing types and upgrade of socio-economic services in the immediate neighbourhood of high rise housing complexes. Technical improvements are not that difficult to make, considering that the standard in comfort, energy saving and functionality of the floor plan for newly built houses has been proven as being technically and economically feasible. The paper highlights the social dimension, namely the problem of shifting occupants, with their low-income budget and many differ-

Summary

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entiated expectations. In this paper the existing standard in functionality of dwellings in relation to comfort and energy saving was addressed. In contrast with established post-war low-rise housing stock, high-rise residential towers are also assessed for their socio-economic problems concerning the organisation of large scale renovation. Two exemplary case studies in the Amsterdam South-East Quarter and in the Delft Quarter of the Poptahof were elaborated to illustrate the practical meaning of improvement of comfort and energy saving in high rise building stock in The Netherlands. DESIGN CRITERIA & COUNTRY CRITERIA MATRIX Following the country contribution papers, design criteria are highlighted as one way how to read a set of parameters summarised in tabulated form, better known as the country parameters matrix. The salient features are pointed out in a brief summary at the end of the matrix, summing up chapter 3. Concluding remarks follow suite. CONCLUSION As typical in most of post-war depressed Europe, fast-track provision of social (low-cost) housing was the key to attracting settlement of families in job-depressed areas, superseding all other priorities. Each country had its own particular social needs, based on traditional state of the art building technology of the day. Today such needs prompted the challenge to take stock of what is recyclable en-mass and refurbish it in the light of its structural integrity and energy efficiency by today’s standards, to the tune of sustainability, for an improved quality of life for future generations.

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Technical Improvement of Housing Envelopes in Cyprus P. Lapithis Design Department, Intercollege, Nicosia, Cyprus

Ch. Efstathiades Lemesos, Cyprus

G. Hadjimichael Town Planning Department, Nicosia, Cyprus

ABSTRACT: The main problems in the building envelopes in Cyprus and the actual standards for existing buildings are being identified. The legislative, natural (climatic boundary conditions) and other influencing factors that lead to the standard solution are being described. Also descriptions of the most commonly used refurbishment actions standard envelopes are being discussed with recommendations on how to solve these problems. The impact of the most commonly used refurbishment actions are being described loooking at the technical, functional, social, economical and environmental on the existing buildings. Finally application methods are being described through two different case studies

1 INTRODUCTION 1.1 Standard envelopes in Cyprus Cyprus gained its independence in 1960 and was proclaimed a Republic. At the period 1960-73 Cyprus went through a fast and almost uninterrupted growth. Despite the breakdown, in the years 1974-75, due to the Turkish invasion and the occupation of 38% of its territory by military forces, the economy recovered soon after and a substantial growth has been achieved. In the years 1975-1993 Cyprus once again witnessed additional economic growth, accompanied by an expansion of social services. Today the people of Cyprus, who live in the Government controlled part of the country, enjoy a high level of education, low unemployment and a good standard of health care. 69% of the population is living in urban areas, which cover 9.6% of the island. The population in 2001, in the area controlled by the Cyprus Government, was 689.565. The total number of units was 286.000 in 2000. Almost 85.000 of these units were built in the period from 1960-1980. Out of the total number of units, nearly 60.000 are apartment blocks and 125, 000 are detached or semidetached houses. The average dwelling area is 189 m2 and the average construction cost is 568 Euros per m2 for the year 2000. The average number of persons per dwelling was 3.23 for 1992 and 3.06 for 2001. In addition to that the number of square meters per person was 49.5 for 1992 and 61 for 2001. Within the context of the housing policy for the refugees, the government of Cyprus has introduced various schemes and programs like the “Low Cost Government Housing Scheme” that provides houses free of charge to low-income families (5.6% of the total number of households were benefited from this scheme). In addition to that the government provides the “Self-help Housing Program on Government Land” (4.1% of the total number of households), the “Selfhelp Housing Program on Private Land” and the “Purchase of a House/Apartment Scheme”. COST C16 Improving the Quality of Existing Urban Building Envelopes – Facades and Roofs. L. Bragança, C. Wetzel, V. Buhagiar, L.G.W. Verhoef (eds) IOS Press, 2007 ©2007 IOS Press and the Authors. All rights reserved.

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Technical Improvement of Housing Envelopes in Cyprus

In the private sector, development and construction companies offer in the free market various types of housing units, mainly apartment or terrace houses. This type of development satisfies nearly 30% of the total demand. A substantial number of families however, choose to build their own detached or semi-detached house, on an individual plot of land, which has an average surface of 520 m2 (68.2% of the total number of households have their own private housing units). Three categories of construction financing have been developed. In the first, a contractor undertakes the construction of the building. In the second, the owner of the property decides to play the role of the contractor-entrepreneur and undertakes the responsibility of constructing and financing the project. He/she usually sells or rents most of the apartments keeping one or two for him/her. In the third (the gradual method of construction), the owner of the property builds one housing unit for the present needs of his/her family, allowing for the possibility of constructing additional apartments in the future to cover the needs of the growing family or merely for investment reasons. The results of this practice are the following:  Lack of planned connection between housing areas and other areas of the city (educational, commercial, etc).  Mixed housing areas with industrial or other areas, dangerous for public health.  Very limited green and open spaces within the housing areas.  Bad relation between street width and building height.  Different housing types even in the same street (large apartment blocks adjacent to low houses).  Unplanned and often unhealthy interaction between the built and natural environment. Contemporary life and the building industry in Cyprus are greatly affected by the proliferation of apartment blocks in the large urban centres. The apartment house became the symbol of the final stage of urbanisation. And since urbanisation is for certain reason a preferable way of living for the contemporary Cypriot; the apartment model is extensively adopted even in medium size settlements in the countryside. 1.2 Requirements in Cyprus, that enforce a reaction to refurbish envelopes The Law (The Minister of the Interior is the Planning Authority), considering the kind of development, specifies the appropriate drawings and any other documents, certificates etc., which they have to be submitted with the application form to the Director of Town Planning and Housing Department and later on to the Municipal Council. Three main issues can be mentioned here. There is not any legal obligation to submit designs or calculations for thermal, acoustic, light and fire performance of a conventional building within the application form. Although civil engineering calculations have to be submitted at the building permit application process, these drawings are roughly checked and the responsibility for any structural failure remains on the civil engineer’s side. According to a recent regulation of 2000 all new constructions, renovations and generally any structure, have to be inspected by authorized engineers. Therefore inspections are compulsory for freelance practitioners, though are not compulsory for Responsible Authorities. For this very reason the enforcement of the Planning and Building laws, is not so effective. All building modifications require a “building permit” and moreover, the modifications that are regarded as “substantial” require an additional “planning permit” in advance. The specific provision is very vague and therefore depends on the discretion of the respective Town Planning Authorities, to judge whether a modification is substantial or not. The painting of a building for example does not require any permit, simply because is not regarded as a substantial modification. There are no specific data concerning maintenance, renovations, and modifications etc. of building envelopes. Indicative data however suggest that the average Cyprus family does not pay a lot of attention on these matters, that people extent as long as possible the various works needed and that they proceed to the necessary works, only when the performance of their building is intolerable, or dangerous looking always for the absolute minimum expense.

Technical Improvement of Housing Envelopes in Cyprus

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No specific legislation was ever passed before 80’s concerning incentives for organized housing complexes. The only regulatory tools were the commonly used town planning restriction which concern plot ratio, plot coverage, maximum height, and maximum number of stories, a general aesthetic framework and some indirect density standards, concerning the minimum surface in relation to the size of housing units. This is actually the very reason that multi-story family buildings were very few till 80’s. Some sort of incentives for organized housing complexes up to three stories, were introduced in the revised statutory local plans in 2003. There are no specific regulations concerning architectural and functional aspects. The authority that is responsible for issuing the Planning Permit, decides whether a certain development rests within the environment of the surrounding area. There are however indirect density standards, concerning the minimum size of housing units. Practice however is much different especially as far as the aesthetic control is concerned. Problems also arise when dealing with the incorporation of small but vital structures, like solar panels, antennas etc. There are specific rules and regulations for new buildings and public uses according to which accessibility to people with special needs, including access ramps and larger toilets in the ground floors, must be provided. 2 SPECIFICATION OF THE TECHNICAL SOLUTION In general the typical housing construction system in Cyprus is based on the conventional construction system, quite common in this part of the Mediterranean Sea. The system comprises the use of reinforced concrete for the load bearing part of the building, which is completed by masonry walls. Prefabrication systems have rarely been used in the past, mainly by the Government in the construction of some low cost refugee estates in the late 70´s. So reinforced concrete, from foundations to the roof applies for the vast majority of the housing constructions. Preliminary regulations concerning the calculation of seismic loads were issued in the late 80´s and that detailed construction regulations were adopted in the beginning of the 90´s. Thus all the buildings built before, may sometime in the future, face possible seismic failure. There is a variety of foundations types according to the type and size of the structure. The most popular are the separate footings with connecting beams and the slab-foundation. The outer skin of a structure, is usually created by the reinforced concrete parts (for the load bearing structure) and a single layer of bricks, (200mm), both coated with three layers of plaster (20-25 mm) and a finishing layer of paint or sprits. The roofs are usually flat concrete slabs, which are covered with light concrete or screed of 50-100 mm for rain-drainage and on top with an asphalt layer of 2-5 mm for humidity insulation. The final touch is given by the use of reflective paints. The last 10-15 years some buildings appeared to form a different top finish with a complete or partial pitched roof. This is used not so much for insulation reasons, but rather for sales promotion reasons since it gives a touch of more domestic or more humane housing buildings. As far as windows are concerned, the vast majority of them are single glazed (4-5 mm) with aluminium frames whereas a small proportion of multi-story family houses, especially after 1980, used double glassed windows. 3 THE IMPACT OF THE MOST COMMONLY USED REFURBISHMENT ACTION ON SUSTAINABILITY TOPICS 3.1 Technical performance 3.1.1 Structural integrity Cyprus has already adopted five compulsory standards concerning the quality of cement, sand, gravel, concrete and brick. The enforcement of these standards lies on three Government bodies, which are, the Mines and Quarries Department, the Public Works Department and the Competition and Consumers Protection Service. It is worth mentioning that by the 1st of May 2004, Cy-

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prus became a full member-state in European Union, and therefore all the relative European standards (Euro-codes, etc.) have to be established in the respective case-law. 3.1.2 Fire protection The bearing structure and any stair of a prefabricated building should provide at least 1/2 an hour fire resistance. The “Cyprus Organization for the Promotion of Quality” chaired by the Ministry of Commerce Industry and Tourism plans to establish quality standards and enforce them as compulsory. 3.1.3 Noise Insulation The “Cyprus Organization for the Promotion of Quality” has already specified some recommended Noise insulation (for 500Hz in dB) Walls (45), Roof (45), slab between floors (50). 3.1.4 Weather and moisture protection The most habitual problem that Cyprus faces is the total absence of damp proofing and thermal insulation of the majority of the housing units. This has direct and severe implications on the energy consumption and the discomfort many people experience. In this case certain parts of the building envelopes, like the roofs and external openings, have to attract more of our attention than others. Besides that one could mention of course some other smaller problems like the moisture problems (due to substandard plumbing installations and poor ventilation) and the poor acoustic insulation (due to light building envelopes). Damp regularly appears in several elements of the buildings, causing surface stains, appearance of humidified and watered surface, color weathering and peeling, detachments, material decay, ruptures and cracks, oxidation of unveiled steel bars and mold formation. 3.1.5 Conductivity (U-value), Heat flow (g-value), radiation, convection The “Cyprus Organization for the Promotion of Quality” has already specified some recommended thermal insulation values for conventional buildings, which however are not compulsory. Thermal Insulation (U value in W/m2°K): Walls (1.7), Roof (2.0), Slab between floors (2.0). 3.1.6

Durability (service life)

No information available. 3.2 Functional / social performance 3.2.1 Flexibility In an attempt to evaluate some of the current housing habits in Cyprus, two questionnaires were compiled (Lapithis, 2002). From the outcome of both questionnaires, it transpired that most dwellings in Cyprus are constructed with little or no insulation and this is the most likely cause for the high percentage of summer and winter discomfort as well as noise complaints. Most other complaints stated (e.g. poor natural lighting) are the result of unsuccessful bioclimatically orientated design. All this suggests the need for better, more bioclimatically appropriate constructions, with adequate insulation and proper orientation with respect to the sun.  A high percentage (69%) of the survey participants experience bothersome noises from the outside, probably as a result of poorly insulated wall surfaces and single glazing which not only allow heat enter and exit freely, but also allow noise to penetrate with little difficulty.  A high percentage of the participants frequently felt cold in the winter (80%) and an even greater number feel warm in the summer (87%).  There were complains about bothersome cold surfaces (70%).  Another problem area, which can be minimized by proper passive design, is the need for artificial lighting (64%).

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 Participants experience drafts from windows and doors (86%). An element of ventilation that can be exploited in a passive system, if it is designed properly.  There is a need for a more widespread use of double-glazing windows in order to minimize moisture condensation on windows (65%), and for a better thermal and noise control.  An interesting fact deduced from the survey is that the overwhelming majority of Cypriots feel safe in and around their house (91%), which makes it easier for a passive solar designer to arrange for ventilation systems requiring frequent openings especially for night time ventilation.  Another advantage the passive solar designer will have in Cyprus is the fact that the Cypriots seem to appreciate the use of shutters (87%), which have been used in traditional architecture.  Of the 13% of participants who did not find shutters an acceptable means of controlling indoor temperatures, most attributed it to the fact the shutters do not work properly. This implies the need for shutters to be placed in front of windows more appropriately planned.  The majority of dwellings have no insulation (66%).  Of the houses that do have some insulation (34%), it mostly is in the form of double-glazed windows and reflective silver coatings (a waterproofing material, which is misunderstood to act as a thermal insulator) rather than in structural constructions, which implies that most insulation in the surveyed houses was more or less treated as an afterthought. 3.2.2 Comfort (thermal, acoustical, visual) The existing legal framework does not incorporate any objective criteria and indices concerning the technical characteristics (like the thermal conductivity (K), the thermal transmittance coefficient (U), the sound reduction index (SRI) etc), the performance of the building materials and the whole structure of conventional buildings. Therefore in most of the cases the free market, especially the local one, does not provide the necessary technical specifications of the relevant advertised products. So only practice can show the real fire resistance, thermal, acoustic and light performance of any housing unit. The aspects relating to external mass are of particular significance for Cyprus due to the large diurnal fluctuations (15 to 25 ºC), and the potential possessed by mass for large solar contribution in winter and cooling in summer. This implies that heat admitted during the day in winter could be stored for use during the evening hours and in the summer could be decapitated in the cool night. Thermal performance of traditional, contemporary and solar houses have been researched in relation to climate and in terms of the various aspects necessary for understanding such performances (Lapithis, 2004). These aspects include architectural design, constructional materials and methods, occupancy patterns and planning. Different architectural and constructional elements and techniques that were used in traditional houses have been studied in relation to their use in passive design today and serve as fine examples of energy-saving architecture. Cypriot traditional houses have proved to be superiorly energy-efficient (243 kWh/m²) when compared to contemporary houses (368 kWh/m²) resulting to the most energy efficient being a passive solar house (121 kWh/m²) due to the thermal performance of all cases based on their architectural design. Cyprus is within the temperate Mediterranean zone. The thermal comfort zone limits (Lapithis, 2002) are 19.5°C – 29°C as the proposed temperature and 20-75% as the proposed relative humidity. The best thermal comfort is achieved in the months of April, May, October and November. These months need no extra heating or cooling. To achieve thermal comfort conditions, ventilation is required in the summer months (June, July, August and September). In the months of December, January, February and March passive solar gains are used to achieve thermal comfort. It must be noted that steps should be taken to avoid over heating in the summer.

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Technical Improvement of Housing Envelopes in Cyprus

Despite the fact that there are some fine examples of contemporary buildings based on correct design principles and a better understanding of the local climatic conditions, the great majority of contemporary buildings are erected without consideration of the climatic conditions and their influence on comfort and the well being of the occupants. This is mainly because due to lack of knowledge about the thermal performance of contemporary constructional materials and methods and to the shortage of building regulations which govern this aspect of the art of building. In most cases, good thermal conditions are achieved by using (energy consuming external and mechanical methods) air-conditioning systems or split units. 3.2.3

Health (air quality, TVOC etc., mould & fungus growth)

No information available. (See also 3.2.1) 3.2.4

Safety, security

No information available. (See also 3.2.1) 3.2.5

Barrier free, accessibility in use

No information available. (See also 3.2.1) 3.2.6 Aesthetical perception Social and aesthetical aspects are usually forgotten because they are not directly related to primary human needs but rather to comfort and quality needs of the people. Designers and contractors prefer the straight-forward solutions, that satisfy the main humans needs. On the other hand, most of the buyers and tenants prefer simpler and cheaper housing units, than buildings or complexes that accommodate “social spaces”. This is because social places will have an increase on the cost of the buildings or the rents. 3.3 Economical performance 3.3.1 Building costs Unfortunately traditional construction methods, techniques , materials etc have been ignored for the sake of fast development and fast profits ( by the building industry) due to the absence of the necessary statutory framework that would guarantee the building quality, but also due to poor awareness of consumers' rights. Due to the age of the buildings many problems are observed. The main problem is their maintenance. The maintenance and the administrative matters of the apartment buildings is entrusted by the residents. In cases where maintenance costs are higher, the agreement of all the residents is required in practice, which often encounters difficulties even in simple administrative matters and often proves to be ineffective in the case of serious repairs or maintenance work on the building. Therefore a lot can be done in this area. The first refers to the statutory establishment of the necessary standards, (concerning not only thermal standards but also acoustic standards as well as standards concerning the dangerous building materials). Today only prefabricated buildings have to meet certain thermal, fire and stability requirements. The second issue concerns the need for licensing the necessary construction details of the buildings. Finally, a last but not least issue, concerns the enforcement of the various permits provisions by the competent authorities. 3.3.2

Running costs (heat losses, cooling, cleaning, inspection, maintenance, etc.)

No information available.

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3.3.3 Increased rent potential vs.vacancies through building action There are many questions on the social aspects that the economical performance of the buildings is affected. Few of these questions need to be answered wit a thorough research:  Owned property vs. rented.  Cost of building construction vs. renting (years of payoff of rent or build or buy).  Developers vs. clients vs. renting.  Prices depending from the location (town or suburbs).  Cost of maintenance- façade, services.  Every how many years is maintenance needed. Lack of investment in building maintenance/conservation vs. high degradation level of facades.  Different owners of a building resulting with serious problems in putting money together.  Old building rental policy plays a role in insufficient execution of maintenance work by the owner. 3.4 Environmental performance 3.4.1 Use of resources (non renewable, renewable) With the exception of solar energy, Cyprus has no other energy resources of its own and has to rely heavily on fossil fuel imports. Energy consumption (non renewable, renewable) - production / assembly - heating / cooling The energy consumption is predominantly oil based. The contribution of solar energy to meet the primary energy needs of the country is estimated to be 5.9%. (Synergy Program, 1995) Thus, more than 94% of the total primary energy is supplied by imports. The cost of imported energy represents 63% of the domestic exports. Due to the developmental nature of the economy of Cyprus energy consumption is increasing at an average annual rate, for the last ten years, at about 6.9%. The total annual energy consumption (electricity included by the domestic sector) in Cyprus comprises of 15.1% with electricity at 34%. Based on consumption by households, a rate of growth of 4.6% is indicated yearly. Breakdown of residential energy consumption in terms of final energy used shows its large share of electricity consumption. In terms of end-use of energy in households, water heating holds the highest place being half of the total consumption, and more than half of the electricity. The present construction trends indicating distinct preference to private, detached houses over apartment flats (60% prefer private detached houses), coupled with higher standard of living (70% of houses are built with central heating) imply a larger energy saving potential in this particular type of dwelling (Ministry of Commerce and Industry, 1994).

3.4.2

3.4.3

Environmental impacts, (GWP global warming potential, AP acidification potential, NP nitrification potential, EP eutrophication potential, ODP ozone depleting potential, POCP photochemical ozone creation)

No information available. 3.4.4 Waste and recycling and re-use potential Not applicable in Cyprus.

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Technical Improvement of Housing Envelopes in Cyprus

4 CASE STUDY 4.1 Case study 1: Low Energy Building The construction was decided to be a concrete frame and floors and roof (constructed as the typical Cypriot contemporary buildings) (Lapithis, 2002). Typical concrete foundations are used for the anti earthquake calculations. The design demonstrates that with an understanding of the principles of environmental physics, appropriate use of available technology and judicious use of materials and resources, it is possible to achieve comfortable living conditions and low energy use. Hourly temperature and relative humidity readings were taken all year round. The indoor temperature remained steady at around 22oC. Overall, the 24-hour indoor measurements indicate a variation of 0-2ºC temperature swing. Taking into account that the external temperature swing is 10-15ºC, this shows that a constant temperature is preserved throughout the day. The building rewarded the inhabitants with a low winter and summer utility bill, considering that no air conditioning system is required. There is an energy saving of 85% comparing the contemporary building with the low energy building. In the construction of the low energy building 13 methods of wall construction and 3 methods of roof construction were taken under consideration. Upon further examination of all viable options for an efficient passive solar building, the chosen type of wall construction is type 6 and for the roof construction is type 1 (Figure 1 and Figure 2). For a passive solar building the walls need thermal mass in order to retain heat. With that in mind, type 11 and 13 listed below are immediately rejected in the case of the low energy building. Types 11 and 13 can be used for passive buildings as long as the walls will not be used as thermal mass. Since the U-value of the wall is an important factor, types 1, 3, 5, 7 and 9 are rejected since they have an unacceptable U-value. Type 10 and 12 have an acceptable U-value, but the high manufacturing cost does not make them cost efficient. The types 2, 4, 6, 7 and 8 are viable options. Type 6, 7 and 8 seems to be the best of at of the 25cm thickness of the concrete frame of the building (beams and columns). A better architectural design is achieved by avoiding the 5cm gap between the external walls and the columns and beams. With these comparisons in mind, the chosen type of wall construction for the low energy building is type 6, since it effectively insulates the whole structure and avoids thermal bridges where the columns and beams occur. Taking into account the advantages and disadvantages of the passive solar system it is concluded that the best systems which can be used for the low energy buildings are Direct Gain, Thermal Insulation and Thermal Storage (Interior Mass). The simplest heat storage approach is to construct the building of massive structural materials insulated on the exterior, to couple the mass of the indoor space. Double-glazed with low emmisivity film and argon-filledare the best windows to use. Shading can be easily controlled for the non-heating season taking into account solar control by use of orientation and shading devices. Natural Ventilation is applied by the use of cross ventilation, stack effect, night ventilation and ceiling fans.

Technical Improvement of Housing Envelopes in Cyprus

Figure 1. Wall construction consideration methods

Figure 2. Wall and Roof construction consideration methods

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Technical Improvement of Housing Envelopes in Cyprus

4.2 Case study 2: Government refugee estate ´´Archbishop Makarios III´ The Government refugee estate ´´Archbishop Makarios III´ is situated in Limassol town, just 3.5 Km from the central area. It comprises two phases (Figure 3 and 4). The first one was build in 1979-80 and the second in 1984-86. It has a total number of 378 housing units, out of which 138 are apartments in three-floor family houses built during the first phase. Buildings followed a simple “cubic form” for functional, economical and practical reasons. No efforts for differentiations were made during the primary construction phase, although some effort were being made during the on going renovation phase. All the multi-story buildings of the estate followed the typical flat slabs concrete structure, filled with plastered bricks as described above. The reconstruction of the buildings was based on typical and conventional techniques and materials. The construction safety was the main issue of this case study. The vast majority of the renovations are related to the construction safety and the stability against earthquake actions. A lot of unnecessary loads, like surrounding walls on top of the buildings or balconies, were removed. The walls were plastered and painted while the roof was damp proofed. No thermal insulation was used either on the walls or on the roof. No specific studies were carried out concerning the building physics. There is no doubt that the general living conditions have been improved a lot. However newly installed air–conditioning units can be seen on some renovated buildings. This indicates that expensive renovations cannot do miracles in a problematic old housing estate and that air split units were reinstalled, after the completion of the renovation works. The average construction cost of the estate (according to 1979 values) was 130 Euro/m2 and the renovation cost (according to 2003 values) is estimated to reach 170 Euro/m2. There is no doubt that direct comparisons may be misleading and that feasibility studies carried out so far, had already taken into account the inflation rate, the cost of living and the final product.

Figure 3. A typical three storey building in refugee estate and typical interventions by the residents to gain some space.

Figure 4. A typical three storey building in refugee estate and typical interventions by the residents to gain some space.

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5 CONCLUSIONS Most building in Cyprus are constructed with little or no insulation, thus causing a high percentage of summer and winter discomfort. The low energy building is designed in accordance to comfort zone calculations so as to ensure the maximum comfort of its occupants. The wall and roof construction plays a significant role in the insulation of the building. The application of the science and art of passive solar architecture to reduce the demand for thermal energy in a building represents a growing area. Retrofitting existing buildings and novel designs of new buildings to this end are a major technical challenge to the near future for Cyprus. At this time, it can be argued that passive design is experiencing a maturity of design applications in which solar energy is utilised in heating, cooling and daylighting buildings. The message here to advance this important beginning, it is that passive design is a sophisticated process to reach simple solutions. Therefore the innovations to look for in the years ahead will be first the development of design methods to enable building professionals to identify balanced and practical solar designs, and second the development of variations of passive solar techniques suited to local climate and resource conditions. This could result to a clearer vision by everyone involved of how passive design is the most cost-effective strategy available in creating an environmentally sound habitat in the climate of Cyprus or any climate of the world. Because of Lefkosia climate, passive solar architecture works to its full capacity, meaning that a passive solar building has 100% energy saving potential. 6 REFERENCES Government of Cyprus. 1972. Town and Country Planning Law (Law 90/72). Lefkosia: Government of Cyprus Government of Cyprus. 1996. Streets and Building Law (Cap. 96). Lefkosia: Government of Cyprus Government of Cyprus. Immovable Property Law (Tenure, Registration and Evaluation – Chapter 224). Government of Cyprus. 1985. Municipalities Law (Law 111/85). Lefkosia: Government of Cyprus. Government of Cyprus. 1984. Ministry of Commerce and Industry and the Department of Statistics and Research. Lefkosia: Government of Cyprus. Lapithis, P. 2003. Solar Architecture in Cyprus. ISES 2003 Conference Proceedings. Gothenburg: ISES Lapithis, P. 2004. “Importance of Passive solar Design in Cyprus”. Proceedings ISES Conference, Orlando, USA. 6-10 August 2005. Lapithis, P. 2004. “Traditional vs. Contemporary vs. Solar Buildings”. Proceedings ISES Conference, Freiburg, Germany. 19-22 July 2004. Lapithis, P. 2002. “Solar Architecture in Cyprus”, PhD Thesis, University of Wales, UK, 2002 Ministry of Commerce. 1998. CYS 98, Cyprus Organization for Standards and Control of Quality. Lefkosia Statistical Service. 2001. Population Census. Lefkosia: Government of Cyprus Synergy Program. 1995. “Preparation of an Action Plan for Improving the Efficiency of the Energy Sector in Cyprus”, Energia, 1995, pp 5-11

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Technical Improvement of Housing Envelopes in Denmark T. Dahl The Royal Danish Academy of Fine Arts, School of Architecture

E. Melgaard The Royal Danish Academy of Fine Arts, School of Architecture

J. Engelmark BYG.DTU, Dept. of Civil Engineering, DTU, Technical University of Denmark

ABSTRACT: The most important reason for renovating Danish housing estates from the post war period has been adaptation to increasing demands on energy conservation, but decay of materials and constructions in the façade, leaking roofs and penetrating water have also necessitated reconstruction and modernisation of façades in the housing stock from that period. The Danish way of renovating is however multifaceted. There is not a single or a general method or technology. The original external walls can be divided in three different constructions: traditional masonry cavity walls, the industrialised concrete sandwich wall and finally the lightweight wooden façade system with plates or boards of wood, fibercement or other materials as cladding. The general problems are most significant for the non traditional built external walls, and they are most commonly renovated by adding an external secondary lightweight construction with extra insulation and new cladding, which might be with or without ventilation behind. The article gives a general description of the performance of the construction and 2 cases representing renovation of sandwich and lightweight constructions respectively. 1 DESCRIPTION OF STANDARD ENVELOPES FOR HOUSING IN DENMARK The typical lay out of apartment blocks in Danish multi-storey buildings has not changed radically over the last hundred years: The basic unit being preferably 2 apartments pr. storey – till the 1930’s served by 2 staircases made of wood, and after by only one made of concrete. The decade 1965-75 gave the biggest rise in new build dwellings ever seen in Denmark. The annual output were in average 45.000 new build dwellings with a peak production of 55.000 (1973) and the lowest 40.000 (1966). This was a result partly of the growth in material welfare and partly because the war situation gave a significant rise in population, which at this time had the resulting effect in needs of dwellings. 1.1 Description of the main technologies Building in Denmark for housing, is in general described as being “traditional” up to the middle of the 20th century, and hereby meaning: the predominant use of the two structural elements/materials: wood- and brickwork, and also including that the majority of the work was concentrated to the actual building site.

The big change came in the 1960’s. Almost all multi storey buildings were then made from concrete, factory made load bearing and bracing elements, vertical as well as horizontal, just as-sembled by crane at the site and usually on foundations/basement cast in situ. Two ways of construction were dominant. One was a system with load bearing transverse walls and non-bearing light weight facade elements. The other was a system COST C16 Improving the Quality of Existing Urban Building Envelopes – Facades and Roofs. L. Bragança, C. Wetzel, V. Buhagiar, L.G.W. Verhoef (eds) IOS Press, 2007 ©2007 IOS Press and the Authors. All rights reserved.

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Technical Improvement of Housing Envelopes in Denmark

with load-bearing facades of sandwich type and spine wall. The first system is far the most common. Other systems based on the use of columns, beams, frames etc. are very unusual.

Figure 1. (left). Facade and lay-out of apartment in buildings with load bearing facades and spine wall, as a minor part of the building stock from the 1970’s and on were build (right) Typical facade and layout of apartments in buildings with transverse load bearing walls, as they were build from the start of the 1960’s and to present days. The system can have a light weight wooden facade construction, but the facade might as well be concrete sandwich elements.

Figure 2. Development of the traditional Danish external brick wall during the 20th century from the massive load bearing masonry wall through the cavity wall to the clay tile-covered sandwich concrete wall.

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Figure 3. Left: Vertical section, Load-bearing concrete sandwich element and slab, (gable). Right: vertical section, lightweight non load-bearing façade element - edge of floor-unit. Both elements have insulations with a thickness of 50 to 70 mm, which is approximately one third of the demand in 2006.

1.2 Requirements in Denmark that enforce a reaction to refurbish envelopes Due to the overheated building situation in the 60'ies many untested building techniques were used and new building materials were applied, first and foremost concrete, steel and lightweight claddings like fibre reinforced cement plates (Eternit). The majority of the technical problems are related to the envelope of the buildings. These problems were mainly caused by lack of durability and insufficient performance against moisture, rain, low temperatures and wind. Concrete surfaces were to a great extend replacing bricks and were considered as durable as the masonry. This would appear not to be true. So the motivation for refurbishment was partly the bad physical condition. But also the changing building legislation played a role. Building in Denmark was from the beginning of the 1960's regulated by a common building code. This building code was different from the former ones by expressing demands in terms of performance of building parts and materials instead of descriptions of the constructions. Anyhow the new demands were based on the minimum performances of the earlier prescribed constructions, so to a start the new building code did not give reasons to a complete delete of the traditional way of building, but made it easier to introduce new materials, constructions and methods. The code was revised in 1966, 1972, 1977, 1982 and in 1995. A new revision has been released in 2006. The most significant change through the years has been regulations for the energy consumption of new buildings. The demands in the code have – until 1995 – concentrated on specifying U-values in every part of the envelope. But from 1995 it has been possible to calculate and estimate energy consumption within certain limits for heat loss and later on limits for the total energy consumption. Until the latest building code there has been a distinction between heavy and lightweight external walls and between high rise (more than 2 storeys) and small buildings (up to 2 storeys) From 2006 there is only a distinction between housing and commercial buildings. Commercial buildings have larger limits, but must at the same time include the consumption from electric powered light and computers etc.

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Figure 4. U-values in external walls, roofs and windows/doors in Danish Building codes from 1966 to 2006

2 SPECIFICATION OF THE TECHNICAL SOLUTION The most often used refurbishment action in Denmark is adding extra insulation to the outside of the external wall, mostly combined with new claddings in steel, wood, ceramic tiles or bricks.

Figure 5: Typical technical solutions for adding extra insulation on lightweight and concrete sandwich external walls.

3 THE IMPACT OF THE MOST COMMONLY USED REFURBISHMENT ACTION ON SUSTAINABILITY TOPICS PERFORMANCE 3.1 Technical performance 3.1.1 Stability, capacity, (earthquake) No serious problems and no greater changes in building codes and regulations have normally caused upgrading and need of improvements in the structural systems. 3.1.2 Fire protection External walls in buildings in more than 1 storey should, according to the building code, be covered with claddings in the so called Class 1 claddings, which means inorganic materials like stone, bricks plaster of lime, gypsum boards or fire-protected plywood and boards.

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3.1.3 Noise insulation. Demands on the acoustic performance of the façade is normally formulated as demands on an acceptable indoor level of noise, which means that the construction must provide an indoor level not exceeding 30 dB. According to the building code of 1961 horizontal airborne-sound insulation in between apartments should be at least 50 dB and vertical at least 52 dB, also including impact-sound insulation. These values would be obtained with e.g. a massive brick-build wall with a thickness of 23 cm – a normal thickness of a wall also fulfilling demands to fire safety. Respectively a floor construction of concrete with a mass of 2400 kg/m3 – either as 12 cm massive concrete cast in situ or as 18 cm of hollow prefabricated concrete slabs, in both cases topped with a raised wooden floor on battens supported on soft material. The building code of 1977 sharpened the demands to 52 dB horizontal and 53 dB vertical. In this code the demands to impact-sound insulation were redefined as demands to the impactsound level in the apartments. The demand was set as a maximum of 63 dB – in practice to be obtained with the same kind of constructions as the ones giving an airborne-sound insulation vertical of the required 53 dB. Now days the demands to airborne-sound insulation are still the same, but the demand to impact-sound level insulation is a maximum of 58 dB. The main acoustic problem in multi-storey-housing estates, which is the transfer of noise from one apartment to another, is seldom taken care of in connection with general refurbishment actions. 3.1.4 weather protection. The Danish climate can be characterized as wet, cold and windy. Mean relative humidity is between 70 and 90 depending on distance to the sea. At this level of humidity most materials are substance to decay, especially those materials preferred as external construction or cladding material in the sixties and seventies. High humidity in combination with frequent change between frost and thaw is harmful to most concrete and cement based surfaces 3.1.5 moisture protection With a climate like the Danish and with a temperature in winter popping up and down around zero degree, the construction of envelopes has always had to be in accordance with this situation. So problems with moisture mostly occur as a result of either bad work in the actual case or by using new and not yet proved constructions – of cause also the combination of the two. An example of this was a wide spread use of flat roofs in the 1960’s and –70’s; now a days in general solved by replacing the old with new ones. The buildings from the period where brick-build external walls were used, have not offered bigger problems than known for centuries and coped with accordingly. The 1950’s with all the experiments in alternative constructions and methods of building gave lessons in how to cope with other kinds of envelopes, but no definite solutions. From the 1960’s and forwards there has been a focus on the construction of envelopes securing that internal produced moisture should not give reasons for accumulation in the construction, and that external water was appropriate rejected. 3.1.6 conductivity, heat flow, radiation, convection st Thermal insulation: As late as 1 of April 2006 the chapter in the code of 1995 on thermal insulation was renamed “energy consumption”, and by this a new attitude was fulfilled. Hereafter the demands are based only on a calculation on the total energy use for heating, cooling, ventilation and hot domestic water in a building and based on the supply for this from none renewal resources; but taking in account alternative supply of energy e.g. from the sun directly. As an alternative to the traditional way of handling thermal insulation, this had all ready been introduced as a possibility in the code of 1995 as originally issued. This so-called energy-frame for domestic buildings is in the revised chapter in the 1995 code defined as: (70 + 2.200/A) kWh per m2 a year, where A is the heated area of the building. Accompanying this overall demand the dimensioning transmission loss for buildings must not exceed 6 W respectively 8 W per m2 of the envelope exclusive windows and doors for buildings up to 3 storeys high respectively higher. Also demands to a minimum U-value of the different building parts are still in force, as described below. But as the overall demands are supposed to

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effectively reduce energy consumption in buildings, the demands to the single building part is rather relaxed compared to the earlier. According to the building code of 1961 external walls should satisfy U-values ranging from a minimum of 0,6 to 1.3 W/m2C determined by the choice of construction. The lowest value being the demand to a light-weight construction (defined as types with a weight less than 100 kg/m2). The highest value was the demand to a heavy one (e.g. a massive brick-built wall with a thickness of 48 cm). Other values in between these were fixed to likewise heavy constructions of different materials/thickness. According to the building code of 1995, as it was issued originally, the same demands were 0,2 respectively 0,3 W/m2C. The lowest value as defined above and the highest to walls with a weight of 100 kg /m2 or more. The latest revision describes a minimum U-value of 0,4 W/m2C. Windows and glazed walls should according to the code of 1961 be “2 panes of glass with a minimum distance of 12 mm” – equivalent to a U-value of 2,9 W/m2C. The original issued code of 1995 prescribed 1,8 W/m2C. The latest revision describes 2,3 W/m2C, which after 1st of January 2008 should be 2,0 W/m2C. The building code of 1961 demanded a minimum U-value of 0.5 W/m2C for floors over basements, solid ground floors and roofs. The same demands in the code of 1995, as it was issued originally, were 0,2 W/m2C. The latest revision describes 0,3 W/m2C for floors over basements and solid ground floors, and for roofs 0,25 W/m2C. The housing stock build before the appearance of the common code of 1961 has originally less U-values than stated here. Far the majority of the buildings were built with massive facades of brickwork or alike heavy materials. Windows were at the most of the type with 2 panes in coupled frames, but often just single paned. Floors and roofs were merely insulated at all. Anyhow all of these buildings have undergone some kind of updating in thermal insulation over the years, partly in combination with (regular) maintenance and/or partly as a result of the oil crisis. This is also in general the situation for the oldest part of the buildings being build according to the code of 1961. 3.1.7 durability (service life) When the new outer lightweight cladding consists of wood, metal-sheets or fiber-cement plates, the durability is somewhat reduced compared to the original concrete surface. At the same time it often demands a regular maintenance process. 3.1.8 functional / social performance  - flexibility, - no comments  - comfort (thermal, acoustical, visual) – no comments  - health (air quality, TVOC etc., mould & fungus growth) – no comments  - safety, - no comments  - barrier free, - no comments 3.1.9 Economical performance  - Building costs. The average cost for repairing damages and upgrading the façade for multi storey housing built in the 60'ies and the early 70'ies is 25 – 30.000 Euros pr flat, but there are quite a few cases showing costs 3-5 times that amount.  - Running costs. A typical rent paid for a 100 m2 flat in social housing around Copenhagen amounts to 1.000 Euros including heat consumption, cooling, cleaning, inspection, maintenance, etc. 3.1.10 Environmental performance  - use of resources (non renewable, renewable) – no comments  - energy consumption (non renewable, renewable) - production / assembly - heating / cooling – no comments  - environmental impacts, (GWP global warming potential, AP acidification potential, NP nitrification potential, EP eutrophication potential, ODP ozone depleting potential, POCP photochemical ozone creation) – no comments  - waste – no comments

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4 CASE STUDIES The following two case studies are typical examples from the period, where the Danish housing stock increased significantly and where the industrial prefab production was the predominantly used building technology. CASE STUDY 1 – COURT-YARD HOUSES, ALBERTSLUND 'Albertslund Syd' was built in 1963-67 by the non-profit housing associations Vridsløselille Andelsboligforening and Herstedernes Kommunes Boligselskab. The structural principle was point foundations, which support pre-cast reinforced concrete foundation beams. The roof is covered with wooden stress-skin elements, supported by the façades and the partition walls. The outside walls of the court-yard-houses are 19 cm thick precast concrete sandwich walls, and the walls towards the garden are storey-high lightweight wooden elements.

Figure 6: Perspective drawing illustrating the assembly of the court-yard house (3 stages – 3 houses)

The courtyard house is brought into this article because of the amount of houses built by this building-system. During the period from 1963 to 1973 there were erected 11 housing estates with a total of 3211 houses, which in a Danish context is approximately 10 % of one years total amount of new houses in that period. The estates are spread around Copenhagen within a radius of 30 miles from the city centre. Before the first estate was 20 years old, it suffered from a number of construction failures and insufficient performances like leaking roofs, dry-rot in the lightweight façade elements, in doors and windows and in the roofs, mould on concrete walls, and week and wavy floors. At the same time the building code prescribed the insulation to be about twice as thick as the original one in both concrete and lightweight walls. It was decided to carry through a comprehensive renovation to restore and update the construction to contemporary building standard.

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Figure 7. Court-yard houses before and after renovation. The original concrete wall was cast in white concrete with a roughly brushed surface.

Figure 8. Section in concrete sandwich wall before and after renovation. After renovation the wall was supplemented with 10 cm extra insulation in a double – horizontal and vertical - wooden structure bolted to the concrete surface and with a cladding of fibre reinforced cement plates between horizontal wooden boards. The extra insulation lowered the U-value from approximately 0,50 to 0,24. The roof was raised and supplied with an extra 10 cm of insulation. The former ventilation space in the old roof was closed.

CASE STUDY 2 – HEDEPARKEN, BALLERUP This second case study is a high rise 3-4 storeys in blocks containing 40 – 60 flats. The development plan was built from 1966 by the non-profit housing association Arbejdernes Andels Boligforening

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Figure 9. Aerial photo of the estate Hedeparken, Ballerup. Only the 7 buildings in the front are refurbished in the way described.

The structural principle is load-bearing cross walls of pre-cast elements, with floor elements of pre-cast hollow-core reinforced concrete elements. The exterior walls are made by wooden elements covered on the outside with grey asbestos cement sheets.

Figure 10. External walls before and after refurbishment. The concrete parapets and the horizontal lines are replaced by vertical parts with balconies and parts with lightweight parapets with tile-cladding

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Figure 11. Vertical section showing insulation, new window and new ceramic tile cladding.

Figure 12. Fotos Ceramic tiles fastened on vertical metal rails

5 REFERENCES Bertelsen, S. 1997 Bellahøj, Ballerup, Brøndby Strand - 25 år der industrialiserede byggeriet. Hørsholm: Statens Byggeforskningsinstitut (SBI) Danish Ministry of Housing, 1997. 22 Overfrakker (22 Overcoats) New Claddings - a collection of examples Engelmark, J. and Melgaard, E. 2004. COST-16, Improving the quality of existing urban building envelopes. State of the art - Denmark Fællestegnestuen for Albertslund Syd, 1964. Albertslund Syd, Teknisk projekt til gårdhuse og rækkehuse. Copenhagen: Byggeindustrien Landsbyggefonden, 2001. Fysisk opretning og forbedring af almene boligafdelinger. Copenhagen: Landsbyggefonden Nissen, H. 1972. Industrialized Building and Modular Design. London: Cement and Concrete Association SBI-rapport 75, 1971. TÆT LAV - en boligform, Eksempelsamling, Hørsholm: Statens Byggeforskningsinstitut (SBI)

Technical Improvement of Housing Envelopes in France Dominique Groleau CERMA, UMR CNRS 1563, Ecole Nationale Supérieure d'Architecture de Nantes, France

Francis Allard LEPTAB, Université de La Rochelle, France

Gérard Guarracino DGCB, Ecole Nationale des Travaux Publics de l’Etat, Vaulx en Velin, France

Bruno Peuportier, CEP, Ecole des Mines de Paris, France

ABSTRACT: The improvement of housing envelopes can play an important role to change the image of the building, to modify the use inside the dwelling, to transform the immediate surroundings of the buildings, to improve the technical and functional performance of the building and to enhance the life environment of inhabitants. In this perspective, and since 1980 in France, rehabilitation of façades has been one of the predominant measures applied to modify, from outside, the image of the building without perturbing the life of inhabitants. From a technical point of view, the main technique used that consists in applying to the existing façade an external skin including thermal insulation offers numerous technical and functional advantages. 1 INTRODUCTION 1.1 Standard envelopes in France In France, in 2002, the number of dwellings/apartments was about 25.000.000 in main homes, whose 77% were built before 1981 and 65% before 1974. The stock of buildings of more than 25 years old shows the importance of the rehabilitation and the neccesity to mantain in a continuous way buildings and the urban environment. But, until today and since the end of the sixties, rehabilitation has been a permanent architectural preocupation, in opposition with the previous massive destructions of whole districts after 1950 carried out against unhealthiness of cities. From 1970, rehabilitation has concerned mainly the "grands ensembles", detached multi-storey buildings designed as the urban expression of the modernity, with their lot of social problems. Over time, the notion of urban heritage has been modified and the fields of intervention have changed to concern not only the 60's urbanisation, but downton and suburbs, private and public housing. Today, with the rapid transformation of society, technology but also way of life, rehabilitation interests every type of building trying to improve housing, regarding as much its technical and functional components as its social and economical dimensions, interesting the architectural level as much as the urban dimension. It is not a question of isolated actions over time but of a continuous preocupation that has to manage the architectural heritage of the near or far past, and at the same time the living environment of inhabitants. Thus, it can be observed that, in France, between 50 and 55% of the construction activity results of maintenance, improvement and rehabilitation. However, out of the private sector, the part of the building heritage that concerns the social housing built from 1955 to 1980 is always one of the main domain of rehabilitation actions, due to the social, economical and urban problems occuring in these areas but also as regard to the importance of the stock they represent and its relative homogeneity (in constructive terms with their reinforced concrete frame, multi-storey buildings, and with the same social characteristics). Some of them have already been renovated in the 1980's and 1990's (1.3 Millions since 1975). Social housing organisms manage more than 3.6 Millions of apartments and rehabilitate more COST C16 Improving the Quality of Existing Urban Building Envelopes – Facades and Roofs. L. Bragança, C. Wetzel, V. Buhagiar, L.G.W. Verhoef (eds) IOS Press, 2007 ©2007 IOS Press and the Authors. All rights reserved.

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than 120000 dwellings per year, and it is estmated that 100000 dwellings have to be rehabilitated per year during the next 10 years. But, since 1980, results of rehabilitation in this sector are considered as limited. In spite of the relative public investments (PALULOS for the public housing, ANAH for the private), the inadequacy of means mainly used up by technical needs (thermal isolation, security...), the lack of concertation with inhabitants and implications of elected representative, and the absence of qualitative improvment in term of attractivity, explain this situation. From now, the rehabilitation solutions propose simultaneously the renovation of the building stock (quality of the dwelling, technical standards), the urban re-development and the social measures that reinforce the insertion of these districts into the city. 1.2 Requirements in France, that enforce a reaction to refurbish envelopes Actual standards and recent regulations (thermal, acoustical, health...) imply new ways to design buildings, but there is no obligatory retroactive effect on the stock of ancient buildings. However, several objectives and actions edicted at the national level encourage and make necessary the improvement of buildings. They are also supported by public and private organisms and associations, that intervene at industrial or informational levels to propose help, prescriptions or solutions for sustainable and environmental devolpments. Particularly, the French objective proposed in the Climate Plan to reduce the energetic consumption in order to divide by 4 the CO2 emissions in France from now to 2050, but also the RT2005 thermal and NRA2000 acoustic regulations lead to action plans, national programs and projects. They impose reinforced standards for the design of new buildings, but higlight also the necessity to find solutions for a massive and energetically performant rehabilitation of existing buildings. In its context, intervention on the envelop of buildings is an interesting mean to answer to theses objectives. The social and urban problems encountered in numerous underprivileged suburban zones, constitute another preocupation field that favours urban rehabilitation operations. But, rehabilitation carried out at an urban level implies to reconsider the way to operate on the buildings. So, normalization of buildings (settings of standards) is a decision that has to be weighted by its impact on the global expected improvement of the dwelling and the district. Thus, the intervention choices on a building requires at first to make a precise diagnosis of the building (state, use, maintenance, environment), then to measure the architectural, technical, human, social and economical impact of the proposed solutions. 2 SPECIFICATION OF THE TECHNICAL SOLUTION Interventions on the 1950-1975 social housing have met three successive periods (Joffroy,1999): the first focusing on technical problems (disorders repairing, thermal insulation...), the second on functional questions (entrance halls, interior of the dwelling…), and then the third with interventions associating the question of the dwelling, the district and the city (social exclusion, private/public spaces, conviviality and proximity...). The interventions on envelopes must take place in this global context that aim to change and improve all aspects of environment and life. Thus, the improvement of façade can play an important role in its expected transformation being a mean to change the image of the building, to modify the use inside the dwelling, to transform the immediate surroundings of the buildings, to improve the technical and functional performance of the building and to enhance the life environment of inhabitants. In this perspective, and since 1980, rehabilitation of façades has been the predominant measure used to modify, from outside, the image of the building without perturbing the life of inhabitants. From a technical point of view, external thermal insulation offers numerous technical advantages with a better energetic performance, the removal of thermal bridges and a possibility of architectural and aesthetic effects. It implies to pay attention to the implementation of that system in order to reduce damages such as the lack of ventilation or the weakness of the structure. Not very used in new building, it is at the present time less commonly used in rehabilitation, mainly due to the impact on the global budget of rehabilitation and the real efficiency of the system. However, many progresses on products, system and implementation were carried

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out and a large set of solutions are proposed for designing performant exernal skins on existing façades. In rehabilitation, external skins are able to integrate the overal constraints, including easy maintenance, protection against pollutions, savety... They become a feasible technical solution, that enables at the same time to change windows and to modify the architectural aspect of the façade (balconies, wall/window ratio, material, color). Six types of external skins applied to the vertical walls constituting the building envelope, are able to include external insulation to reduce efficiently energy consumption; they are (reVetir, 2004, Buttenwieser,1997):  thin or thick cement rendering upon insulation; this technology is largely dedicated to the rehabilitation in France,  light coat made of insulating granular elements, that gives a suplementary insulation,  weather boarding applied to the existing wall with thermal insulation,  insulated wall panels; they associate a covering and an insulating material (often polystyrene); they represents 10% of insulation technics and are used essentially in the social housing.  the "vêtage" is a traditional principle that consists to fix up manufactured elements directly on the wall support, without framing, with thermal insulation,  attached covering of thin stones with thermal insulation.

Figure 1. Several types of external skin: cement rendering, weather boarding, insulated wall panel, "vetage" according to Buttenwieser, I.,CSTB 1997

Each of these system can be applied on every type of buildings whose external vertical walls are made with concrete blocks, walled concrete or prefabricated concrete. A classification based on performance criteria is proposed that takes into account: repairs facility, maintainability, wind pressure resistance, tightness, impact resistance, fire-resistance rating, thermal resistance. Based on site characteristics, environmental situation or climatic conditions and costs, performances can be explicitly identified and a system selected that will be more in adequacy with the imposed constrainsts. 3 THE IMPACT OF THE MOST COMMONLY USED REFURBISHMENT ACTION ON SUSTAINABILITY TOPICS The most commonly used refurbishment applied to buildings in social housing is the application of an external skin on the existing façades. It corresponds to the apparition of the external insulation in France from 1974, in order to reduce the energy consumption and to insulate non insulated buildings; so its real use is focused in the refurbishment market and mainly in the frame of rehabilitation of block of flats. Several technologies can be applied depending on the state of the façade, its structure or its architectural shape and the possible investment. But each of them shares common characteristics and properties that gives a real efficiency to this type of solution. So, detailed and specific properties of each possible technology, presented in the previous paragraph, will not be described in detail in terms of performance, but mentioned only when a very different behavior can be observed for a particular solution.

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3.1 Technical performance 3.1.1 Stability, capacity, resistance Generally, the external skin is tied to the structure, either directly, without frame, upon the existing wall of the façade, either indirectly through an intermediate frame or light structure fixed up to the wall. So, the stability is primarily maintained by the wall and the structure of the building. Generally, the type of structure used commonly during the sixties and seventies with the formed concrete or tunnel formworks techniques offers a very stable structure. Only the way to fix the second skin and elements that forms the external skin has to be adjusted to maintain the stability of the second skin itself. However, the most outer layer of the skin has to be impact resistant. Five classes of impact are considered in technical guides concerning the level of impact exposure (expressed according to French norms in Kg/J) , depending of the position of the skin in the façade, at the floor level or in a non accessible or protected location. Generally the cement rendering has a better resistance to impacts than insulated wall panels. 3.1.2 Fire protection Various experiments carried out on whole system including skin and insulation have enabled to impose levels and minimal requirements to be applied. These requirements help then to choose an appropriate technique among the available technical solutions. Generally applied to non attached buildings, accessibility to fight fire is then well insured. 3.1.3 Noise insulation Generally the social housing built during the period 1959-1970 are now included in the dense urbanization, often submitted to the nearby important traffic noise. Then, the tight external skin enables to reduce considerably the air tightness, thus air and sound infiltration. The effect of the added external thermal insulation plays also an important role in the acoustic absorption property of the whole façade. The sound attenuation obtained by the use of a mineral wool can reach 5 dB(A); equivalent performance can be obtained with elastified polystyrene, but not extruded or expanded polystyrene. In any case however, the solution cannot be wholly performing without improving, at the same time, the acoustical level of windows. 3.1.4 Weather protection The external skin is quite a natural way to protect inner rooms against the weather attacks. It acts as a second skin that plays a global role of protection against water, against non controlled air ventilation, against pollution lead by wind and rain, again heat penetration and so on. However, moreover of the simple wind resistance of this second skin that has to be controlled, two elements have to be considered: the air and the water tightness. 3.1.5 Moisture protection Four water tightness classes are proposed to distinguish external insulation systems: the first does not inhibit the water to reach the wall support; the second inhibits the penetration up to the support; the third has some disposal to catch the water behind the external skin; the last comprises a water tightness skin with a possible way to retrieve water. A weighted factor is applied according to the exposure level to the wind and enables to define the obtained type of wall. However, an important attention has to be paid about the ventilation system in order to not create internal disorders in the building due to a too important air tightness. 3.1.6 Conductivity, heat flow, radiation, convection The main effect of the insulated second skin is to reduce considerably the thermal losses and energy consumption. The use of low conductivity mineral wool and polystyrene in a layer to 6 to 8 cm gives a global thermal resistance of the wall about 1.5 to 2.5 m2.K/W that corresponds to the required performance of the thermal regulation. It is also an efficient way to suppress the existing thermal bridges between floor slab and walls. Another improvement related to the weather protection effect is to mitigate the uncontrolled air penetration, so lowering the thermal losses due to convective exchange. The solar effect is also reduced and does not reach the wall of the structure. So thermal shocks that can affect the façade are avoided and the inertia of the wall can play its positive role during summertime.

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3.1.7 Durability Being a protection system against outdoor aggressions, the external skin play an important role in the durability of the building (structure, concrete, iron corrosion). But the second skin has to be maintained itself over time. Being generally a light structure, very accessible by outer, the maintenance can be easy. However, the cement rendering upon insulation is a technical solution that can demand more maintenance due to fissuration and cleaning than others solutions built upon a light structure. Many weather boarding elements are self-cleaning, therefore resistant to pollution and mosses. Inversely, boarding elements can be less resistant to impacts and when, broken or pulled out, have to be replaced very quickly to maintain safe the global protection of the external skin. 3.2 Functional / social performance 3.2.1 Flexibility The external insulation skin enables easily to change the façade, mainly to modify the windows distribution or to reduce the glasses ratio of façades. It is also a performing way to correct defaults or light disorders of façades and to change the architectural aspect of the building. 3.2.2 Thermal, acoustical, visual comfort The second skin can improve considerably the comfort inside the buildings. In summer, the internal inertia of the protected concrete wall mitigates the elevation of indoor air temperature; and, the protection of the walls against sun exposure inhibits the elevation of wall surface temperature. In winter, with the external insulation layer, the walls are maintained to a sufficient temperature and are not perceived as cold surfaces by inhabitants. The acoustical performance of this technical solution contributes to lower the level of outdoor noise but can inversely, due to the decrease of the ambient noise level, bring to light internal noise from neighbouring apartments. The visual effect of the external skin is mainly perceived from outside by people walking in the site; the second skin, by modifying architectural aspect of the building, can therefore participate to create a new image of the building and of its environment. One of the main benefit of this technical solution is that it improves the global indoor conditions by clothing the existing façade, therefore masking imperfections, defaults and defacements of the existing façade and creating a new attractive one. 3.2.3 Health The external insulated skin maintains a good protection against outdoor constraints (heat and cold, noise, rain, wind and air infiltration) and therefore participates greatly to the global comfort and health of inhabitants. Another social benefit (but also economic) comes from the fact that this kind of technical solution enables to keep people staying in their apartment without creating an unbearable situation during construction. Generally, this technical solution implies, by performance coherence, that windows are also changed to answer to the actual technical standards. The new windows can be then in some cases located in the outer wall surface, so adding an available space in the width of the window frame to manage new fittings and modifying the visual relationship between indoor and outdoor. 3.3 Economical performance 3.3.1 Building costs, As mentioned just previously, keeping people in their dwellings during work does not involve a cost overrun due to the non occupancy of apartments. The costs of the external insulation skin are dependent of the type of the used technique. In 1999, costs could vary from 40 Euros by m2 for the cement rendering up to 80 and 90 Euros for the system including a weather boarding. They depend also of the type of building and the desired level of rehabilitation.

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3.3.2 Running costs Important gains can be obtained from this type of technical solution. The reinforcement of the width of the thermal insulation and the control of air infiltration contribute for a large amount to reduce, in dwellings, the energy cost during the heating period. It is generally admitted that the percentage of thermal gains can reach up to 30% but the real economy will result of the specific characteristics of the used solution ( insulation thickness) and of the previous situation. In term of cleaning, many coatings are nowadays self-cleaning, reducing therefore the necessary periodic cleaning of the external skin. However, maintenance can be increased in case of board constituted of small elements (as slates, ceramic tiles) more exposed to wind and less shockresistant that have to be replaced from time to time. 3.4 Environnemental performance 3.4.1 Energy consumption With this kind of technical solution, the energy consumption is considerably reduced with the insulation layer. The maximum insulation thickness seems to be 8 to 10cm. In summer, the protected internal inertia prevents again excessive indoor heat, so reducing the need for fresh air conditioner. 3.4.2 Use of resources and environmental impacts They depend greatly of the type of material used and of the thickness of the insulation layer. Moreover, the field of technical solutions to achieve the external skin is very open; a large choice of systems and material enables to choose performing solutions that have a reduced impact on environment. However, the selected solution has to be assessed in terms of sustainability. 4 CASE STUDY Façade renovation of a dwelling block, La Noue, Montreuil, France Situation: Montreuil, Seine Saint Denis (93) FRANCE Participants: Contracting Authority : OPHLM Montreuil Architect : Ligne 7 Architecture (Paris) Energetician : Armines (Paris), MVE (Montreuil) Local authority : Mission environment, town of Montreuil Type of rehabilitation : façade of a four storey building built in 1969 Renovation date : 2001-2002 4.1 Context of the renovation operation The municipality of Montreuil, near Paris, has launched a green neighbourhood pilot project to renovate, with the municipal social housing office, 500 apartments. In one building, a more efficient energy renovation program was performed in the frame of the European REGEN LINK demonstration project. This program integrates the successive steps of the renovation process, design, construction, commissioning, monitoring, reporting and dissemination; so it enables to have a complete report of this operation including simulation, measurements and a tenants survey (Peuportier,2002,2004). 4.2 Objectives The general objective is to demonstrate that, in existing building and in the social housing sector, it is possible to achieve high environmental and energy performance. More specifically, for the renovated apartments block, the aim is to reduce the heating load by 60% and, by a large amount, the CO2 emissions.

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4.3 Description before renovation The four storey building of 52 social dwellings represents a floor area de 4500 m2. It is heated by a district heating using mainly coal fuel. Built in 1969, the building has no thermal insulation and uses a large area percentage of single glazed windows in façades. The load bearing structure is composed with reinforced concrete shells and concrete floor. The heating load before renovation was estimated to 170 kWh/m2/year. 4.4 Main design and technical measures proposed for rehabilitation The proposed rehabilitation measures are largely based on bioclimatic potentialities of the building that faces to the south and therefore can benefit solar gains, but also on internal layout with living rooms located in the south façade and bedrooms to the north. The main measures and techniques involved in this project were:  To install external insulation with reinforcement of the insulation thickness,  To use advanced glazing (with low emissivity and argon layer) instead of standard double glazing,  To adjust glazing properties (in surface, in solar transmission) according to the south or north orientation,  To design some glazed balconies, as solar collectors, in order to preheat ventilation air and reduce thermal bridges,  To enable crossing ventilation in summer thanks to the double orientation and to benefit of the strong inertia of walls and floors.  To propose additional measures in order to save domestic water or to reduce ventilation heat losses using a moisture control system. 4.5 Technical performances 4.5.1 Thermal performance The insulation standard corresponds to an external insulation layer of 6cm width. In the project, a 10cm thickness was adopted to contribute to reduce more drastically the heat losses. The external insulation inhibits the thermal bridges (specially at the slab level) except to the balconies. It is why it was proposed to glaze several balconies and to use them as solar collectors (preheating of the fresh air). The type of glazing is low emissivity, with a U value of 1.7 (1.1 in some apartments where argon has been used). Hard coating low emissivity has been used in glazed balconies, with a solar factor of 0.72 enabling a higher solar transmission : the U-value is a little higher, i.e. 1.9 W/(m2.K) but the global energy balance is improved compared to soft coating. The glazing area has been reduced by 50% in the north façade in order to reduce heat losses, and by 20% in the south facade (increasing the heating load by 2% but improving the economic balance of the project). 4.5.2 Ventilation, humidity A moisture control system was installed in order to control the air flow according to indoor humidity, leading to a reduction of the flow rate when the apartments are not occupied. The external insulation is protected by a weather boarding that insures water tightness of the façade. 4.5.3 Noise protection The external insulation and the advanced glazing with its two layers contributes largely to the protection of apartments from the outside sound. 4.5.4 Recycling, Durability The weather boarding, made with recycled material (cellulose), is a high pressure laminate with an exceptional resistance to impact and moisture.

38

Technical Improvement of Housing Envelopes in France

4.6 Functional and social performances 4.6.1 Thermal comfort The improved insulation of the building and the night thermal mass help to protect apartment from overheating in summer period. In winter, the reduced heat losses helps to maintain easily a comfortable indoor ambiance, but generally with higher indoor air temperatures after renovation. The glazed balcony is technically interesting but is difficult to manage when tenants are absents; the absence of ventilation and high temperature can damage plants. 4.6.2 Humidity Measures shows that internal humidity stays between 30 and 50% when heating is on. Before renovation, similar values were measured. 4.6.3 Daylighting and visual comfort Illuminance measurements during diffuse sky days shows that the obtained levels are satisfactory, with 200 lux in living rooms. The daylight factor has not significantly changed by the reduction of glazed area, but some people complain that they cannot so easily look outside. 4.6.4 Acoustical comfort The external insulation and particularly the advanced glazing have considerably contributed to increase the acoustical insulation of the dwellings from outdoor airborne-sound. However, tenants inform that noise is transmitted from others dwellings; maybe the reduction of the external noise level (background noise) is responsible of the emergence of internal noises. 4.6.5 Air quality Air flow and air quality are more controlled after renovation. Air flows are adjusted to hygienic and sanitary constraints but some people feel like not having enough fresh air. 4.6.6 Inhabitant behaviour As it can be see in the tenants survey, the building before renovation was not a performing building but it was not systematically perceived by inhabitants as being uncomfortable. Building transformations affects directly tenants that often compare the new situation with previous one. Generally satisfied with the renovation, tenants however formulate some comments and critics. For example, some people feel cold due to a lower temperature of radiators whereas the indoor air temperature is 23°C, or perceive negatively the reduction of glazed area that limits their outside view, or still complaint the lack of fresh air. Technical performances are thus sometimes not totally efficient due to the behaviour of tenants that open windows to get new air or leave open doors between living room and glazed balconies. Discrepancy between calculations and measurements is partly explain by the various types of occupancy and it needs time and cooperation in order that people adjust their behaviour with the new situation. 4.7 Economical performances The building renovation cost was 3500 Euros per dwelling corresponding to about 41 Euros/m2 of floor. The supplementary investment cost compared to a standard renovation was 185000 Euros. The annual energy saving is about 12000 Euros, so the pay back time is about 16 years. More precisely, the pay back time is estimated to 2 years for low emissivity windows, but up to 20 years for increasing the insulation thickness. Some measures are not particularly economical like glazed loggia but their impact must not be limited to the only thermal dimension; the loggia contributes also largely to the attractiveness of the living room. Apartments owned by OPHLM of Montreuil will be rented during the next 30 years, so life span of external insulation, windows, glazed balconies and district heating loop is expected to be also 30 years. At the same time due to renovation, rents for the tenants have been increased.

Technical Improvement of Housing Envelopes in France

39

4.8 Environmental performances 4.8.1 Energy consumption Energy consumption measurements carried out in the building after renovation shows that energy heating consumption reduction was reduced by 32%; it was expected by calculation a reduction of 60%. Two main causes explain this difference. The first one is due to the increase of indoor air temperature greater than 3°C after renovation that creates a 22% supplementary thermal load. The second one results from improvement of certain parts of the building; thus, the heating of ground floor produces an additional energy consumption, estimated to 25%. Consequently, after correction, the reduction of heating energy consumption can be estimated to 50% that corresponds to an energy consumption of 70 kWh/m2/year. 4.8.2 Water consumption In order to reduce the water consumption, a low flow-rate sanitary equipment was installed. In the shower system, a Venturi effect increases the speed of water flow producing an equivalent comfort level but with a smaller water flow. This efficient water system has enabled to reduce water consumption up to 30%. 4.9 Environmental impact A life cycle assessment was performed. It shows that an important gain was obtained to reduce up to 50% the CO2 emission. In the first year, renovation has enabled to avoid the emission of 76 tons of CO2 and further corrections proposed can still improve the situation. Several others indicators were assessed, like acidification, eutrophication, human toxicity or waste; comparatively to the previous situation, the renovation performs better scores for all the targets. 4.10 Field of application This renovated building is very representative of a large amount of buildings built in the sixties before the introduction of a thermal regulation in France. Thus, the type of techniques and measures proposed in this renovation can be easily apply, specially external insulation and performing glazed windows. Data collected in the survey can also serve to better manage the rehabilitation procedure by favouring people participation to the global renovation process. 5 CONCLUSIONS This kind of renovation operation shows the necessity to follow with the help of experiments and surveys the behaviour of the building after renovation in order to measure the real impact and performances of design and technical solutions proposed in the renovation. Side effects, maybe more important in renovated existing buildings than in new buildings, can then be observed as the increase of indoor air temperature or a modified use of spaces by inhabitants. In the previously analysed operation, some adjustments were proposed, for example, to lower the heating loop temperature and to better observe the performance of glazed balconies. It is important also to convince building advisor, municipalities and inhabitants that solutions are efficient over time and without risk for people. It can be seen for example that technical performance improvement in existing buildings can modify considerably the way of life of inhabitants, at least the way to perceive the new things relatively to the previous situation. More generally, results shows that rehabilitation concerns all actors (community, owners, architects, contractors, technical experts, manufacturer and inhabitants…) and that the true success of a renovation operation is strongly dependant of the level of implication and acceptance of each one in the project.

40

Technical Improvement of Housing Envelopes in France

Figure 1. The building before renovation

Figure 2. The building after renovation

Figure 3. Layout of the district

Figure 4. The glazed balconies

6 REFERENCES Buttenwieser, I. Panorama des techniques du bâtiment 1947-1997.Plan construction et architecture. CSTB. 1997 Classement reVETIR des systèmes d'isolation thermique des façades par l'extérieur. Selection 2004 des produits pour l'habitat et les équipements collectifs. Groupe Moniteur. 2004, pp. 32-33. issued from Cahier du CSTB 2929, livraison 375, décembre 1996 EDIF, Energies durables en Ile de France, brochure Agence Nationale de l'Environnement et des Nouvelles Energies Ile de France, janvier 2004 Enveloppe du bâti: l'innovation n'est plus prioritaire. Dossier spécial HLM, n°245 septembre 2004, les Cahiers Techniques du Bâtiment, pp75-78 Joffroy, P., La réhabilitation des bâtiments, conserver, améliorer, restructurer les logements et les équipements. 1999. Collection Techniques de conception, Le Moniteur, Paris, France. Logement social, les nouveaux axes de réhabilitation. Dossier, n° 227 septembre 2002, les Cahiers Techniques du Bâtiment. Peuportier, B.,Deliverable D5 : final technical report including monitoring results and analysis. REGEN LINK, site 4 La Noue, OPHLM de Montreuil et ARMINES, 2004 Peuportier, B., Assessment and design of a renovation project using life cycle analysis and GB tool. Sustainable building conference, Oslo, 2002. Réhabilitation des grands ensembles. Architecture d'Aujourd'hui. N°194, 1977

Technical Improvement of Housing Envelopes in Germany Christian Wetzel CalCon Holding GmbH, Munich, Germany

Frank-Ulrich Vogdt Institut für Erhaltung und Modernisierung von Bauwerken e.V. (IEMB), Berlin, Germany

ABSTRACT: The improvement of housing envelopes can play an important role to change the image of the building, to modify the use inside the dwelling, to transform the immediate surroundings of the buildings, to improve the technical and functional performance of the building and to enhance the life environment of inhabitants. In this perspective, and since 1980, rehabilitation of façades has been one of the predominant measures applied to modify, from outside, the image of the building without perturbing the life of inhabitants. From a technical point of view, the main technique used that consists in applying to the existing façade an external skin including thermal insulation offers numerous technical and functional advantages. 1 INTRODUCTION 1.1 Standard envelopes in Germany The German climatic boundary conditions do not vary a lot. Regarding heat degree days (based on 12°C) the values vary between 4623 [Kd] in Hof in the Eastern Bavarian hillside region close to the Czech border and Freiburg in the upper Rhine-valley with 3178 [Kd]. The solar radiation varies from 53 [kWh/m²] (December value for Harzgerode in northern Germany to 608 [kWh/m²] (July value for Garmisch in southern Bavaria). According to these climatic boundary conditions heating and warm water production are contribution to the energy consumption of the building stock. Cooling energy is only necessary in modern office buildings with large window areas. The heating period in Germany usually starts October 1st and ends April 30. In 1985 the first regulation for energy saving in construction passed the German parliament. From that time on every new building had to fulfill certain heat insulation requirements. This means for buildings younger than 1985, that acceptable heat insulation is already existing. Nevertheless these buildings contain only around 12,5% of the whole dwellings in Germany, meaning that around 87,5% of the German building stock were built without legal obstruction to fulfill a certain heating energy demand. The energy directives issued since 1985 also contain requirements for existing buildings, e.g. for facades: if more than 25% of the existing cladding of one side of the building façade have to be removed caused by a refurbishment action, the whole side of the façade had to reach an U-value lower than 0,4 [W(/m²K]. In most cases this reduced U-value only can be reached by implementing an additional insulation layer on the façade. But, as the energy directive for existing buildings was not coupled with a fine or penalty most building owners in Germany did not obey to the directive. Beside the legal obligation the development of new building materials as well as the customers/users requirements for proper indoor environment quality with according reduced "cold" radiation from inside of exterior walls caused also in the years before 1985 improvements of the thermal insulation of the building envelopes.

COST C16 Improving the Quality of Existing Urban Building Envelopes – Facades and Roofs. L. Bragança, C. Wetzel, V. Buhagiar, L.G.W. Verhoef (eds) IOS Press, 2007 ©2007 IOS Press and the Authors. All rights reserved.

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Technical Improvement of Housing Envelopes in Germany

1.2 Requirements in Germany, that enforce a reaction to refurbish envelopes The below listed values are an excerpt and not complete list from the current energy directive in Germany. If more than 20% of one façade orientation of a building are being "changed", the following U-values have to be fulfilled: First implementation of a wall, complete replacement of a wall, implementation of an additional interior layer on the exterior wall or new fillings for timber constructions:

U < 0,45 (W/m²K)

Implementation of an additional layer on the exterior side of the wall, implementation of insulation layers and, if the cladding of an existing wall with more than U > 0,9 [W/m²K] is being replaced

U < 0,35 (W/m²K)

Windows on façade and roof (with exception +0,1 for special glazing, e.g. additional sound insulation etc)

U < 1,70 (W/m²K)

Non openable fixed glas-elements (also with exception +0,1 for special glazing)

U < 1,50 (W/m²K)

Flat roof (heated area to outside air)

U < 0,25 (W/m²K)

Sloped roof (heated area to outside air)

U < 0,30 (W/m²K)

Ceilings and walls to unheated areas

U < 0,40 (W/m²K)

Walls to ground

U < 0,50 (W/m²K)

2 SPECIFICATION OF THE TECHNICAL SOLUTION Extenal thermal insulation composite systems (ETICS) are used in the first place to improve the thermal protection of external wall constructions and are becoming increasingly more important.

50 45 sales [mio. m²]

40 35 30 25 20 15 10 5 97

95

93

91

89

87

85

83

81

79

77

to 76

0

Fig. 1: Number of thermal insulation composite system areas [m²] laid annually in Germany.

The first ETICS were developed in the 1950s. In these polystyrene rigid foam plastics battens were bonded onto the supporting base using plastic dispersion adhesive and then covered with the reinforced rendering (Fig. 2). From the mid 70s ETICS mineral fibre boards were used that are bonded to a supporting base and dowelled (Fig. 2). In the 80s systems mineral fibre lamellas were also used. In the 90s varied systems were developed using other types of insulating mate-

Technical Improvement of Housing Envelopes in Germany

43

rial made from wood fibres or mineral foam plates (foam concrete), however no adequate long term experience is available for these yet. a) Oberputz bewehrter Unterputz Polystyrol

Verankerung Schiene (siehe Detail) Oberputz

Kleber teilflächig

bewehrter Unterputz

KS-Mauerwerk

Wärmedämmung Klebepunkt Dübel

b)

KS-Mauerwerk Oberputz bewehrter Leichtputz

Detail

Bohrung Ø 8.2 / 10.2

Fig. 2: (a) Bonded polystyrene system (PS-ETICS), (b) Bonded and dowelled mineral fibre system (MFETICS), (c) System with rail mounting (from [1])

Along with the purely bonded or bonded and dowelled systems, systems with rail mounting (Fig. 2) were offered for modernisation, these could be used where the base surface is unfavourable. The development of possible cladding variants has become very diverse in the last few years. Along with the rendering systems – such as pure synthetic resin plaster or modified plastic mineral plaster – brick strip or natural stone claddings are offered. 3 THE IMPACT OF THE MOST COMMONLY USED REFURBISHMENT ACTION ON SUSTAINABILITY TOPICS 3.1 Technical performances 3.1.1 Struktural integrity Proof of stability of ETICS is shown within the framework of the technical approval procedure. When the requirements for the building inspection approval are adhered to in respect of - proportion of adhesive surface, - number of dowels dependent on the base surface and wind load zones, as well as - the material properties of the individual components (e.g. transverse tensile strength). then the stability of the thermal insulation composite system is guaranteed. In the case of systems that are bonded only, then the unevenness of the base surface must be a maximum of 1cm/m. In the case of bonded and dowelled systems it is 2 cm/m and in the case of systems with rail fastening 3 cm/m. The maximum thermal insulation material thicknesses are limited dependent on the respective system (e.g. PS-ETICS d 400 mm) In the case of normal base surfaces, such as brick, concrete or lightweight concrete walls, proof of stability for the wall itself is not necessary, as the additional loads from the ETICS are limited as a rule to 35 kg/m². In the case of light constructions such as e.g. walls of wooden post-and-beam construction, proof of stability may be necessary.

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Technical Improvement of Housing Envelopes in Germany

Special dowels for anchoring in thin layers of concrete are offered for dowelled systems for three layer elements with thin facing shells (dd 6 cm). ETICS do not increase the stability of the existing supporting structure. 3.1.2 Fire protection ETICS may only be used in Germany in building heights up to tower block height (Hd 21 m) as flameproof systems (that also means using PS-ETICS). In the building expansion joint area use of a strip made from non-flammable insulation material (e.g. mineral fibre boards sheets or mineral fibre lamellas) may be necessary in accordance with building regulations. Where the heat insulation thickness of the polystyrene rigid foam plastic is over 10 cm, use of non-flammable heat insulation is required in the lintel area of wall openings. Where buildings exceed tower block height (>21 m), the use of non-flammable systems is necessary. 3.1.3 Noise Isolation ETICS can cause the existing sound insulation against external noise to improve as well as deteriorate. An example of this is shown in Table 1 for an existing single shell construction using an existing sound insulation of Rw, = 54 dB. Table 1: Improvement and deterioration of the sound insulation of an existing external wall by fitting ETICS (+ = improvement - = deterioration).

bonded PS-ETICS bonded PS-ETICS with more elastic PS

rendering g d 10 kg/m² - 2 dB 0 dB

rendering g > 10 kg/m² -1 dB +1 dB

bonded and dowelled PS-ETICS

-1 dB

-2 dB

bonded MF-lamella-ETICS bonded and d = 50 mm dowelled MFd = 100 mm ETICS PS-ETICS with rail mounting

-5 dB

-5 dB

-4 dB -2 dB

+4 dB +2 dB

+2 dB

+2 dB

3.1.4 Weather Protection and moisture protection The weather protection of an existing external wall construction can be improved considerably by fitting ETICS. The weather protection of the ETICS itself is in particular determined by the rendering system. ETICS with water-repellent renderings can also be used in areas with the highest degree of stress from driving rain. Renderings are water-repellent when the capillary water absorption w and the diffusion of vapour equivalent air space thickness sd is limited. As can be seen from Fig. 4, most rendering systems show water-repellent properties. In the case of existing monolithic external walls made of brick or concrete the diffusion of vapour requirements for moisture are guaranteed. In the case of light constructions such as e.g. external walls of wooden post-and-beam construction, proof of vapour diffusion may be necessary.

Technical Improvement of Housing Envelopes in Germany

45

Fig. 4: Evaluation of 170 different ETICS in respect of the water-repellent properties of the rendering systems.

The material combinations of insulating material and rendering system must be adhered to in technical approvals. This means for example that the use of a relatively vapour diffusion tight artificial resin rendering system on mineral fibre insulation that is open to diffusion is not permitted. Some people are afraid, that the fitting of ETICS reduces the possibility for the wall to "breathe" and therefore the interior moisture problems are increased. This argument has been tested several times and was proven wrong. Only a fraction of the moisture occurring due to the use of the rooms is transported outside by way of vapour diffusion and that is independent from whether there is a ETICS or not. The more effective way to the power of ten is the removal of moisture by means of ventilation. 3.1.5 Conductivity (U-value), Heat flow (g-value), radiation, convection Improvement of the thermal protection is dependent on - the heat transfer coefficient U of the existing construction and - in particular the thermal insulation thickness d and the thermal conductivity O of the insulating material. Fig. 3 shows an example of the improvement of the U-value of an existing construction (Uexisting = 1.5 W/(K.m²)) dependent on the thickness of the thermal insulation material and the thermal conductivity of the material.

Fig. 3: U-value of a wall after fitting a ETICS.

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Technical Improvement of Housing Envelopes in Germany

3.1.6 Durability (service life) ETICS have proven themselves in the long term. Cautious estimate on the life expectancy of thermal insulation composite systems is given in [2] as 25 to 45 years, on average 30 years. ETICS have considerable influence on the increase of the remaining durability of the existing construction. After fitting ETICS the existing construction behind it dries out in the long term (Fig. 5).

Fig. 5: Long term drying out of the concrete facing layer of a three layer external wall element after fitting a polystyrene-ETICS (from [3]).

The equilibrium moisture content in the concrete then falls under a critical value of 80%. Below this moisture content corrosion of the reinforcement can be excluded. Fitting a ETICS therefore stops the corrosion process. 3.2 Functional/social performance 3.2.1 Flexibility ETICS can not contribute to an increase in flexibility in the inside of the building or in the external area. 3.2.2 Comfort (thermal, acoustical, visual) ETICS improve the thermal comfort. Fitting additional thermal insulation measures increases the temperature of the inside surface of the external wall (Fig. 6).

Fig. 6: March of temperature through the external wall without and with ETICS

This reduces the heat loss due to radiation from the human body to the colder external wall. The “operative” – that is the sensed – temperature increases at the same room air temperature. People find this more comfortable. The acoustic comfort can be influenced in a negative manner by ETICS. When the sound insulation dimension is improved against external noise (Section 2.1.4) it is possible that noise

Technical Improvement of Housing Envelopes in Germany

47

from the neighbouring apartment is perceived as disturbing, as the basic noise level falls due to the external noise. The possibility of improving the visual comfort by fitting ETICS is limited to the external area. Only by selecting the cladding, rendering, clinker strips or natural stone can the aesthetic appearance be altered. There is however no considerable change to the aesthetics or the design of the whole building. 3.2.3 Health (air quality, TVOC etc.,mould & fungus growth) As described in the section above, fitting ETICS increases the internal surface temperature of the external wall. At the same time the danger of mould fungus formation drops. 3.2.4 Other functional or social properties Other properties, such as social benefit, security, breaking down of barriers etc. cannot be quoted in connection with the fitting of ETICS. 3.3 Economic Performances 3.3.1 Building Costs The set up costs for ETICS are on the one hand dependent on the type of the system (Table 2) and on the other hand on the arrangement of the façade. Table 2: Set up costs for thermal insulation composite systems in Germany costs [€/m²] from

to

avarage

PS-ETICS (d = 10 cm) with synthetic resin-based rendering

63

75

70

PS-ETICS (d = 10 cm) with mineral rendering

68

80

75

MF ETICS (d = 10 cm) with mineral rendering

78

98

90

3.3.2 Running Costs (heat losses, cooling, cleaning, inspection, maintenance, etc.) Fitting additional thermal insulation measures reduces the transmission heat losses through the external wall. The reduction in operating costs connected with this must be compared with the investment costs. An example of this: In the case of brick-external wall construction the rendering needs to be renewed. A feasibility study should be carried out to see if additional thermal insulation measures are useful. The costs for renewing the rendering and fitting a thermal insulation system as per table 3 are put in comparison here. The amount of difference results in the “energy related” extra costs of 22 € per m² component area.

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Technical Improvement of Housing Envelopes in Germany

Table 3: Building Costs ETICS [€/m²]

renewed rendering [€/m²]

Gantry, cleaning Renewed rendering / coating ETICS (d = 12 cm) Edge protection profile, movement joint profile Starter profile, window sill, rainwater downpipe, roof parapet

10 44 2

10 34 3

10

-

Others, fee of architect

13

10

total 79 “energy reduction related” extra costs: 79 – 57 = 22 €/m²

57

Based on an interest rate of 5.75%, a price increase of 5.4% and taking the service life of the thermal insulation composite system as 30 years, as well as the assumption of natural gas heating at 0.02 € per kWh, the amortisation time is as shown in Fig. 7.

Fig. 7: Amortisation time as intersection for the investment costs and the energy cost saving.

As the amortisation time lies clearly under the service life of a ETICS, the measure is economical. The annuity profit is determined in order to determine the economic optimum thickness of the thermal insulation. In so doing the extra or reduced costs of 1.25 € per cm thickness of thermal insulation material and per m² are applied (Fig. 8).

Technical Improvement of Housing Envelopes in Germany

49

Fig. 8: Annuity profit

The annuity profit is at its highest in the range between 8 to 14 cm. This corresponds to the economic optimum thermal insulation thickness. It is recommend that the upper range, that is 14 cm thickness of thermal insulation material is fitted in view of further increases in power prices and the external costs for environmental pollution etc. that are not considered. 3.4 Enviromental Performances 3.4.1 Use of Resources (non renewable, renewable) The proportion of renewable resources is very low in the case of the usual market system. This proportion only increases in the case of insulating materials made from sustainable raw materials – such as wood fibre boards. There is however insufficient experience to date in respect of the long-term resistance of these systems.

PEI [kWh], GWP [kg-CO2 ], AP [g-SO2 ] per m² and year service life

3.4.2 Energy Consumption (non renewable, renewable) – production / assembly – heating / cooling The proportion of renewable energies in the production of ETICS is low. Fig. 9 shows the overall energy content from primary energy content for the production and primary energy requirement due to the transmission heat losses dependent on the insulation thickness for a PS-ETICS

50 PEI

40

AP 30

GWP

20 10 0 0

50

100

150

200

thickness of thermal insulation [cm]

Fig.9:

Overall energy content, global warming potential and acidification potential over the life cycle of a PS-ETICS dependent on the insulation material thickness.

50

Technical Improvement of Housing Envelopes in Germany

It shows that when the insulation material thickness continues to increase to approx. 50 cm, the overall primary energy content reduces further. Therefore the energetic optimum is not yet achieved by the present insulating material thicknesses. 3.4.3 Environmental impacts, (GWP global warming potential, AP acidification potential, NP nitrification potential, EP eutrophication potential, ODP ozone depleting potential, POCP photochemical ozone creation) Fig. 9 shows the global warming potential as well as the acidification potential over the whole life cycle of the ETICS dependent on the insulation material thickness for the above mentioned example. In this example the optimum thermal insulation thickness in respect of the global warming potential at approx. 75 cm in respect of the acidification potential would be approx. 25 cm. 3.4.4 Waste and recycling and re-use potential There is little information on the contribution to waste made by the manufacturing phase. Pure uncontaminated polystyrene rigid foam plastics offcuts could be passed on for material recycling. In the case of external wall constructions using ETICS, which no longer meet the requirements for thermal protection, the existing systems do not necessarily have to be removed and replaced with new ones. Rather more procedures are offered which enable “over insulation” that is fitting an additional ETICS on to the existing ETICS. Apart from the thermal recycling of PS-ETICS, no other possibilities of recycling are known. 4 CASE STUDY 4.1 Residential Building in Frankfurt, Gallusviertel As an example for the refurbishment including the energetic improvement of the façade the area "Gallusviertel" in Frankfurt can be highlighted. Altogether houses with around 2500 apartments were refurbished with an insulation of 12 centimetres of ETICS (some even in the passivebuilding standard with 26cm). Besides new windows (double, coated and gas filled), insulation of roof floor 10 centimetres and cellar ceiling 8 centimetres were applied. In addition on some houses balconies with thermal separation to the façade system were fitted on the façade.

Fig.10: Houses before and after the refurbishment action.

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51

5 REFERENCES Cziesielski, E.; Vogdt, F.U.: Damage to thermal insulation composite systems, Stuttgart, Fraunhofer-IRB Verlag, 1999. Handbook Sustainable Construction from the Federal Ministry for Transport, Construction and Housing (publisher) Berlin, 2001. Vogdt, F.U.: Stress on thermal insulation composite systems as a consequence of hygric and thermal deformations on facing layers in large panel construction, Dissertation, TU Berlin, 1995.

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Technical Improvement of Housing Envelopes in Hungary A. Zöld Budapest University of Technology and Economics

T. Csoknyai Budapest University of Technology and Economics

ABSTRACT: The main problems of the post-war block of flats in Hungary are the poor thermal performance: thermal bridges, bad whether proofness and air-tightness and the related fabric damages, resulting in high operational cost and low quality of living standard. Uncontrollable heating systems increase the waste of energy. Although several good initiative can be referred to in the past as well as recently, some refurbishment attempt which neglected the complexity of the system further increased the problem, sometimes making disputable the rationality of the applied measures. False, simplified calculation concepts of pay-back time slowed down the decision making and the allocation of funds for added thermal insulation. On the other hand successful demo projects proved the great energy saving potential and positive side effect of thermal rehabilitation.

1 INTRODUCTION As it is described in the “State of the Art in Hungary” chapter the typical blocks of flats built in the post-war period are made with prefabricated sandwich panels. With regard to the huge number of flats in these blocks on one hand and the refurbishment programmes of the state, offering financial contribution exclusively for this building stock, on the other hand, the recent analysis encompass this type of buildings. The thermal performance of these buildings is not acceptable any more. The heating energy consumption is very high (150-220 kWh/m2year), accompanied with fabric damages. In the period of their erection the minimising the in situ work, high level of prefabrication meant the priority and the energy price was 1% of that of the recent figure. 1.1 Main characteristics of exposed walls Based on an overview of the available constructional plans five characteristic periods can be distinguished from the point of view of thermal performance and fabric protection. The periods are presented in Table 1. Although these were typical values, they were not uniform. Certainly in all periods there were differences, because the building elements were produced in sixteen prefabrication factories and plants. The dates were also not so definitive. Thus, the figures presented in this paper are useful for good estimations. COST C16 Improving the Quality of Existing Urban Building Envelopes – Facades and Roofs. L. Bragança, C. Wetzel, V. Buhagiar, L.G.W. Verhoef (eds) IOS Press, 2007 ©2007 IOS Press and the Authors. All rights reserved.

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Technical Improvement of Housing Envelopes in Hungary

Regarding the theoretical U-values one could think that these structures are rather acceptable and almost fulfil even the present requirements. Certainly, if these were real U-values the measured heating energy consumption of the buildings were much less. As a consequence it is obvious that either the U values are much higher or there are other components of heat loss not taken into consideration. Indeed, both are true and the unconsidered components are the thermal bridge losses.

Table 1: Characteristic periods of the industrialized constructions Period Period 1

-1965

Period 2

1960-67

Period 3

1967-74

Period 4

1974-82

Period 5

1982-92

Characteristics Medium blocks, generally slug concrete, no thermal insulaton Sandwich panels, 8 cm mineral wool insulation, no insulation at joints Sandwich panels, 8 cm mineral wool insulation, 2-3 cm insulation at joints Sandwich panels, 7 cm PS insulation, 2 cm insulation at joints Sandwich panels, 8 cm PS insulation, 8 cm insulation at joints

Theoretic air-to-air conductance U = 1,3..1,7 W/m2K U = 0,45..0,66 W/m2K U = 0,45..0,66 W/m2K U = 0,45..0,55 W/m2K U = 0,38..0,48 W/m2K

1.2 The real air-to-air conductance of sandwich panels One reason is the mistakes made during the prefabrication process when sandwich panel was treated with heat, water, vibration and the polystyrene layer was not protected from the negative influences of the regular technology. In addition the weight of the reinforced concrete layer represented significant pressure on the PS layer. As a consequence the PS plates have often broken and their insulating performance has significantly decreased. An example for this problem is shown by the infrared photograph in Figure 1. Measurements in the Laboratory of Building Physics at BUTE have proved that this prefabrication technology causes 50 % of deterioration in the insulating properties. In period 2 and 3 mainly mineral wool was used as insulation material. The last decades have proven that this material can easily move due to its fibrous and loose structure. Therefore in many cases the mineral wool has fallen down in the panel. Today in many of these panels the mineral wool layer is missing causing very high U-values and fabric degradation. In addition the insulating properties of mineral wool significantly decrease at high moisture content. It causes problem if the driving rain can enter along the edges of the panel to the insulating layer. Naturally this problem is not typical for period two when the panel edges were not insulated. Here the concrete rim has a protecting effect. On the other hand the thermal bridge losses here are the highest.

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Figure 1. Thermal bridges caused by panel junctions and broken PS insulation (infrared photo)

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Figure 2. Thermal bridges caused at junctions, window and parapet installations (infrared photo)

The infrared photos give evidences on the constructional mistakes. On Figure 1 the insulation is broken in one of the panels. The thermal bridges at panel junctions and around window frames can clearly be seen in Figures 1 and 2. In addition to the poor performance of the applied insulation the thermal resistance is decreased also by the steel reinforcement crossing the insulation layer that fixes the external weather protection concrete layer to the load bearing concrete layer. 1.3 Point-like thermal bridges in the sandwich panels The problem is typical after the 2nd period, when the concrete connection at the edges of the to reinforced concrete layers was eliminated and substituted by steel reinforcement. The number and diameter of crossing-through steel elements depends on the licence of the technology. In a most frequent panel of Soviet type 2x7 = 14 crossing steel elements with a diameter of 8 mm were applied. Although the total cross section of the steel elements are almost neglectable compared to the insulated area, the heat loss is significant, because the heat conductance of steel is steel / insulation = 80 / 0,05 = 1600 times higher than that of the insulation. Furthermore the extra heat loss caused by the crossing steel elements cannot be calculated only from the ratio of the surfaces and conductances of steel and insulation, because the steel elements do not finish at the meeting plain of the concrete and insulation layers. They enter into the concrete layer and turn in order to ensure the necessary holding stability. Therefore exact calculation can only be made using finite elements’ method. To simplify the calculation procedure the Passive House Institute has developed a diagram that can be seen in Figure 3.

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Heat loss of point-like thermal bridge

Steel Wood Screw GFK steel Diameter

Figure 3: Determination of extra heat loss caused by poctual thermal bridges (eg. steel elements crossing through the insulation) (Source: Passive House Institute)

It can be read from the diagram that the most frequently applied crossing steel elements with 8 mm diameter has a heat loss of 0,03 W/K, that means 14 x 0,03 = 0,42 W/K heat loss per panel. Let’s consider a panel of 2,65x3 = 7,95 m2 with 7 cm insulation including a window of 2,1x1,5 = 3,15 m2. The laboratory U-value of the panel is Ulab = 0,5 W/m2K, thus the laboratory specific heat loss (not including he linear and ponctual thermal bridges) of the panel is (7,953,15)x0,5 = 2,4 W/K. Adding the 0,42 W/K extra heat loss caused by the steel elements the result is 2,88 W/K and the increase is 17,5%. In general the extra heat loss is 10-20 % depending on the panel type and the additionnal elements (windows, balconies, loggias, etc.). Now it is clear that determining the exact U-value of a panel installed decades ago is impossible with calculations, because it depends on several stochastic parameters: the quality of fabrication and the climatic influences during its lifetime. The realistic value can be estimated from measured heat consumptions or laboratory measurements of panels. According to laboratory measurements at BUTE Laboratory of Building Physics the U-values of the uninstalled panels are between 0,8-1,1 W/m2K depending on the age, the applied system and the stochastic effects.

Figure 4. Example of a junction typical for buildings made with medium-sized blocks

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2 HEAT LOSS OF PANEL JUNCTIONS Parallel to the layers the junctions have also being developed with the time. In the followings the junction types are presented in the order of construction time. The thermal bridge losses were determined by a computer aided model based on the finite elements’ method. 2.1 Period 1: Single layer, uninsulated structures In the first period ended around 1965 slug concrete structures had a dominating role. Slug concrete is a relative light porous material with a lower U-value than that of the concrete (Oslug concrete = 0,5..0,7 W/m2K, Oreinforced concrete = 1,55 W/m2K). These structures were built without any insulation and the U-values of the facades are high: U = 1,3-1,7 W/m2K. Two technologies were applied: cast structure made at the construction site and siteassembly using prefabricated blocks. Due to the homogenous structure the significance of the thermal bridges is lower than that of the following periods, the typical W @

U Q TB >%@ 1dim TB  Q1dim ª W º «¬ m 2 K »¼

209 112 112 112 98 Q1dim >W @

75 317 156 193 106 Q TB >W @

36% 2,03 284% 3,07 140% 1,92 173% 2,18 109% 1,46  U 1dim TB QTB > %@ Q1dim ª W º «¬ m 2 K »¼

325 173 173 173 152

90 397 198 235 132

28% 229% 114% 135% 87%

1,91 2,63 1,71 1,88 1,31

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3 EFFECT OF ADDITIONNAL THERMAL INSULATION ON TRANSMISSION LOSSES 3.1 Added external thermal insulation The typical and only rational solution to improve the thermal characteristics of the exposed wall is to add external insulation, covered with thin plaster (the DRY-WIT or Thermohaut /=thermal skin/ system). The insulation itself is PS or mineral wool, the thickness was 6 – 8 cm before, nowadays 10 – 12 cm becomes typical, due to the new national regulation. The effect of thermal insulation on the laboratory U-value is shown by the diagrams of Figures 8 and 9 for a typical panel. The first centimetres of the insulation cause a dramatic improvement and then it becomes more and more modest. If the insulation is put on the external side of the wall not only the one-dimensional U value decreases but also the thermal bridge losses, because the insulation covers the free way of the „escaping” heat. Using the thermal bridge model the