Ebook: COST C16 Improving the Quality of Existing Urban Building Envelopes

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.

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 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 life-cycle 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.

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

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.

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 light-weight 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.

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.

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.

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.

Buildings make a large contribution to the energy consumption of a country therefore a very large potential for energy savings exists 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 stock of buildings. Major renovations of existing buildings above a certain size should be 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. The effort is not yet finished. Reducing the energy consumption in buildings built in 50's and 60's is, at first, a complex issue in reduction of energy consumption in a technical sense, as well functional, social, economical and environmental aspects. Therefore for refurbishment of the facades as the most appropriate technical solution is selected “Externally Insulated Façade System”- EIFS. In this paper the impact of this technical solution regarding refurbishment of the facades and improving the energy efficiency of the buildings will be discussed.

The principal problem of residential building envelopes in Malta is that there was never a deliberate effort to use insulation in cavity walls, be it for thermal or acoustic isolation. 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. This paper looks at the various technical improvements that could be implemented to the building envelope that could achieve improved energy efficiency as well as a notable upgraded comfort level for a better quality of life.

Paper presents one of the first popular technologies widely used in Poland for upgrading thermal resistance of facades in multi family housing buildings made with the use of non traditional technology. As a reaction to more restrict requirements of energy consumption, it became popular in 1980s years of the last century due to its material and technological simplicity resulting in relatively low construction costs.

The idea of External Thermal Insulating Dry System (ETIDS) consist in adding to existing facade insulating sheets covered by external layer panels with structural frame, and fixing it to original wall structure. Although 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 the large panel building technologies – the most popular technology of multi dwelling building in Poland.

Description of the 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.

The main problems in multi-storey building envelopes in Portugal are the low thermal insulation and low airborne sound insulation. These problems are more relevant in buildings built before the publication of the first thermal code. The envelopes, mainly the façades of buildings built in that period, do not fulfill the actual users comfort requirements and construction codes. This way, it is necessary to find the most appropriate technical solutions to refurbish those façades. One of most used technical solutions is the ventilated façade. In this paper the impacts of this technical solution in standard envelopes are going to be discussed. The impacts will be assessed looking at technical, functional, social, economical and environmental proprieties.

In Slovenia typical residential buildings from 1946 to 1980 have either masonry or reinforcement concrete structure. The envelopes built before 70-ties are without thermal insulation with double glazed box windows; but in 70-ties 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. Recently, national regulation (2002) imposed some obligatory measures at envelope refurbishment, which are supported by subsidies for energy efficiency. Different technical solutions for envelope insulation improvement are common in Slovenia, but most frequently the external thermal insulation system with thin layer plaster is used, accompanied with multi-chamber PVC windows with low-e double glazing. In this paper the impacts of technical solutions in standard envelopes are discussed from technical, functional, social, economical and environmental aspects. The refurbishment case study reflects the contemporary approach to refurbishment.

Renovation of high rise apartment buildings in The Netherlands has just been executed, is at hand now or is planned for the nearby future. Typical problems are lack of thermal comfort, loss of functionality of the floor plan and social deterioration of the neighborhood. Changes of the dwellings in the housing complexes should include energy saving, alteration of the floor plan functionality in more differentiated housing types and upgrade of socio-economic services in the immediate neighborhood of the high rise housing complexes. The technical improvements are not that difficult to make, considering that the standard in comfort, energy saving and functionality of the floor plan for newly build houses has been proved being technical and economical feasible. The problem is the organizing of the existing inhabitants, with their small budgets and many differentiated expectations. Financing the insecurities of this kind of logistical processes is forming the bottle-neck.

In this paper the existing standard in functionality of dwellings in relation to comfort and energy saving will be addressed. In comparison with this standard the technical problems of high rise building stock will be addressed. Next the paper will shortly address the socio-economical problems concerning the organization of large scale renovation of high rise complexes in The Netherlands. Two exemplary case studies in the Amsterdam South-East Quarter and in the Delft Quarter of the Poptahof will be elaborated to illustrate the practical meaning of improvement of comfort and energy saving in high rise building stock in The Netherlands.