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