New Standards for Old Houses. Sustainable Renovation Concepts for Houses on Estates Built Between the Wars and Post-War
In the times of economic crisis between the wars and after the second world war many housing estates made up of detached houses were built in Austria as part of publicly funded housing programmes. The houses on an estate were all constructed according to a uniform plan, subject to the principles of economy and necessity. The smaller of these estates, which still partly retain their uniform appearance, have an average of 30 houses, but larger estates with up to 200 houses were also built.
This type of housing estate house was also often copied by individually constructed houses built between 1930 and 1965.
The house types hardly display regional characteristics and were built according to an almost identical plan throughout the country and also in other European countries such as Germany. Due to their compact and uniform method of construction, they are especially suited to the formulation of standardised renovation packages.
The low-cost method of construction means that the houses have an inferior building fabric, high energy figures, outdated installations with high energy loss and low-ceilinged cramped rooms with low incidence of light. A high and realistic potential for renovation can be expected as a result of the generation change. Partly we can start from the assumption that the subsequent generation already live in their own house and there will be unoccupied dwellings as a result.
Examples of this kind of house which have already been renovated show that with optimal renovation planning for this type of building savings of up to 77% are possible in heating energy consumption.4 Furthermore, a study of the Niederösterreichische Landesakademie comes to the conclusion that with 70%, by far the greatest part of energy-saving potential is to be found in the renovation of detached and semi-detached houses.
The primary aim of the project was for an interdisciplinary project team of planners, social scientists and technicians to draw up guidelines and basic principles for renovation containing everything from advice and suggestions (measures for alterations and extensions to improve housing quality, optimisation of energy use etc.) to concrete renovation packages. The aim is to reach the standard of a low-energy house or a passive house. Well thought out solutions whose costs and benefits have been calculated and checked and in which the potential for saving is widely known should motivate the implementation of sustainable renovation and eventually counterbalance the current information deficit.
On the basis of documented examples of housing estate houses in various regions of Austria and Germany and from the results of previous projects, the research team could start from the assumption that:
- during the period of construction studied the construction methods and building materials used varied very little,
- this type of housing estate house has hardly any regional characteristics and
- all measures worked out for this type of housing estate dwelling can be applied independently of region or federal province.
Due to the representative proportion of detached and semi-detached houses built in the period between 1930 and 1960 and available previous studies which could be drawn on for further examination, the whole federal province of Lower Austria was selected for the first survey of housing stock and three model municipalities in Lower Austria were chosen for the survey of residents and the structural survey.
On the basis of a wide-ranging review of the housing stock in the first phase of the project, fundamental characteristics of the housing estate dwelling from between the wars and post-war were combined to make a prototype which represents a high percentage of existing housing estate dwellings in size, ground plan and building structure. Location, orientation and degree of renovation as other variables enabled the creation of a universal model from which the renovation packages can be worked out. Parallel to this, a survey of residents provided information about satisfaction, wishes, ideas, problems, motives and incentives for or against renovation. Designs for alterations and extensions have also been drawn up which on the one hand integrate energy-saving measures and on the other bring appropriate improvements in line with the wishes of the residents.
The results have been worked into detailed guidelines with concrete planning and implementation information which are on the one hand intended to guide residents in the renovation and improvement of the heating quality of the housing estate house and on the other to provide the information wanted by the residents.
Results and conclusions
Basic evaluation and survey of housing stock on existing estates of detached and semi-detached housing estates (research area: Lower Austria):
The continuing trend in the construction of detached houses:
The high number of detached houses constructed each year confirms the continuing trend towards the owner-occupied house as the preferred form of housing. According to housing statistics in Lower Austria alone 4,500 new detached houses were built in 2002. In Austria 17,000 dwellings were completed in detached and semi-detached houses in the same year. In contrast to this there was a relatively low percentage of new apartments created in existing buildings and a relatively high stock of existing detached houses, which from the points of view of energy use and comfort no longer meet today's standards. In 2002 in Austria 7,693 apartments were completed in existing buildings through adaptation, extension and rebuilding, in Lower Austria only 1,420 apartments. Both figures include all apartments which were built in multi-storey apartment houses and lead to the conclusion that only a small percentage of apartments are created through rebuilding or extension of detached houses.
The potential for renovation:
- Building stock: in the construction period between 1919 and 1960 throughout Austria a total of 222,700 dwellings (approx. 18%) was built as detached houses. In Lower Austria, which in this study is also examined separately, almost 25% of all detached houses built, in figures 80,000 dwellings, were constructed between 1919 and 1960.
- Renovation rate of buildings: a first survey of housing stock on some of the larger estates showed that the windows had already been changed in the majority of buildings but that hardly any thermal renovation of the facades or renovation of the roofs had taken place. On many of the larger estates the appearance of the estates has remained very uniform. The building of extensions took place in very different ways in different regions.
- Quarter related renovation measures: in a survey of 121 Lower Austrian local authorities 88 of the councils questioned (73%) reported that they had an estate of detached houses built between the wars or in the post-war period. The regional distribution shows a very high percentage of estates in areas with earlier industrialisation (the southern Vienna Basin and southern Lower Austria and in the region around Sankt Pölten) and a very low percentage in more agricultural areas such as Waldviertel and Weinviertel. Renovation measures which could be applied to all estates and could contribute to additional cost savings were therefore particularly suited for this type of house. However, the survey of residents showed that the owners still had significant reservations and uncertainties about measures which would have to be carried out jointly.
Survey of structural conditions and potential for savings (research area: model municipalities Schwechat, Purgstall and Neunkirchen):
The energy-saving potential:
The survey of structural conditions based on selected housing estate houses showed that the energy index of this type of house is three to four times higher in comparison to today's standard for new houses (85 kWh/m²a). The relative proportions of possible energy savings are approximately as follows:
- Through insulation and complete conversion of the attic floor approx. a third of the heat requirement can be saved.
- With additional insulation of the exterior walls almost two thirds to three quarters of the heat requirement can be saved.
- The heat requirement can be reduced by another 10% by insulating the cellar ceiling.
- Fitting a ventilation system brings only a further saving of approx. 5%.
Our investigations show that with the appropriate renovation packages the energy requirement of existing unrenovated housing estate houses can be brought up to today's standard for newly-built houses (70-85 kWh/m²,a) or to that of a low-energy house (<40 kWh/m²,a).
Socio-scientific survey: Quantitative and qualitative survey of owners and key actors (research area: model municipalities Schwechat, Purgstall and Neunkirchen):
The need for renovation and the owners' wishes for renovation:
Generally speaking large-scale renovation work has already been carried out on all estates in recent decades. However, some of the renovation work was carried out so long ago that renovation once appears to be necessary. In comparison to the total stock only few houses have not been renovated at all. Based on the results of the surveys, the two focus groups made up of owners and experts and the interviews with experts, the following conclusions may be drawn:
- There are usually several motives behind a comprehensive renovation of an old building: increased ease and comfort, the necessity of carrying out repairs, the desire for better room division or additional rooms as well as an economical form of financing through public promotion of old buildings.
- The earliest renovation works took place 40 years ago. It must be reckoned that these houses will need to be renovated again relatively soon. Few of these houses are still in their original condition and are only renovated if there is a change of owner (through inheritance or sale).
- Comparing the average time-period since the renovations with the average period of use of the individual building components, it is the heating system which most requires renovation. The model calculations show that that there is considerable potential for saving costs and energy in these housing estate dwellings.
- Interest in alternative sources of energy is rather low. The attitude to the type of energy used - mainly gas - can be seen as rather pragmatic because gas has been widely advertised by EVN in recent years.
- There is strong interest in information about products and companies, especially about measures for saving energy and improving comfort (full thermal protection, windows, solar energy, ventilation system etc.). However, there is little willingness to pay for these benefits.
- There are large information deficits in relation to the improvement of individual building components such as with full thermal protection because renovation procedures are wrongly planned: first renewing the heating system, then the windows and only as a later step is thermal insulation carried out.
- Decisions are made rather in accordance with aesthetic aspects than with structural and technical necessities (full thermal protection creates deeper window recesses, which are described as "not looking good").
- The interest of younger people, especially young families, in sustainable raw materials is rather high. However, in the end the price is the decisive factor in the decision for or against ecological materials.
- With regard to changes in room division there are wishes for more open ground plans, direct access from the living space to the garden as well as larger storage spaces (garden equipment, workshop, bicycles etc.)
- The financing of partial renovation will also in future rather be assured by private sources. Owners often work on their own houses. Loans are mainly taken up for comprehensive renovation (at a generation change or sale) and for larger renovation works such as on the facade and roof.
- Owners who are interested in renovation look for comprehensive and comprehensible information about the various opportunities for grants. Hardly anyone is in favour of a joint renovation of whole housing estates because of the fear that it will be impossible to reach decisions about a common product and period of renovation.
Renovation guidelines, renovation packages:
Investigation of the energy index in a prototype estate house worked out from the stock survey showed that the energy index can be reduced by up to 8% of the original level with ambitious thermal renovation. Along with this it would be possible to cut CO2 from an original 11,000 kg to approx. 1,800 kg. These figures impressively show the great potential for the renovation of detached houses from the construction period 1930 to 1965.
Because on the one hand it will only be possible to motivate residents and owners towards ambitious thermal renovation through the interplay of the widest range of measures and, as shown in the survey, renovation is most frequently carried out at individual initiative and in the form of the renovation of individual building components, well-presented specialist information material which is up-to-date and available will be especially important.
An important result of this research project is that detailed renovation guidelines have been worked out on the basis of the structural housing stock survey and the survey of residents. The guidelines contain concrete planning and implementation details for renovation and improvement of the thermal quality of the house and take account of the improvements desired by residents and the information they require. The renovation guidelines are in the appendix to this final report and are available in electronic form as an individual file.
In most federal provinces provisions for energy and climate protection measures have also been integrated into renovation grants. Supplements of higher percentage grants are provided as motivation to improve the energy-saving capacity of the exterior of the building. The difference in grant is based upon stipulations of the maximum permissible energy indexes, minimum U-levels to be achieved or a higher grant requires the attainment of certain heat transmission coefficients of individual building components (U-levels). In some federal provinces the creation of new housing space through the rebuilding, adaptation or extension of existing buildings is promoted through new housing construction grants.
The renovation guidelines give comprehensive details of federal province grants as well as grants for alternative energy systems and energy-saving systems. The final section of the guidelines deals with the subject of "Financing" and gives detailed information about various financing possibilities.
The results of the investigations and surveys obtained during this research are the most important basis for the following recommendations. The recommendations aim to promote sustainable and ecologically orientated renovation in the detached house sector in a targeted way by identifying approaches to remedy the problems.
- Renovation advice!
Where it is possible to exert an influence, such as when allocating grants, obligatory expert renovation advice could work against mistaken trends. The aims and results of renovation advice should be clearly formulated and besides advice about the technical implementation of the individual renovation measures, also in cases of single measures, it should include the drawing up of a sustainable total renovation plan. Increased promotion of targeted training and further training for renovation advisors who are independent of companies would therefore also be worth considering.
- Improve the level of information!
In order to make up for the current information deficit, the interaction of very different factors must be taken into consideration. In addition to the above-mentioned advice, a positive effect could be produced by the increased presence of the theme of sustainable renovation in a wide range of media. However, information activities should not be confined to users but planners and builders should also be targeted.
- Information about costs and cost comparisons!
The widely-held opinion that the actual costs of renovating an old house are difficult to calculate in advance and that all renovation work therefore brings the risk of uncertain costs is a considerable impediment to the decision to renovate an old house rather than to build a new one.
In addition to information about sustainable renovation plans and the use of alternative materials for renovation, where costs can be calculated and forecast simple access to independent information about costs, support in making a realistic estimate for various renovation measures and help in making cost comparisons between different renovation plans which also take the savings potential into account could contribute to the acceptance of sustainable renovation plans.
- Qualification measures!
As previous studies have show and has again been confirmed by the results of this project, the level of knowledge about the use of sustainable raw materials and energy-efficient renovation measures is not only rather low among consumers but also in construction companies carrying out the work. Targeted qualification measures for workers and companies could promote more knowledge about the use and application of alternative building materials.
- Company networks!
The setting up of company and sector-spanning networks which together offer optimum coordinated sustainable renovation and guarantee the professional quality of their work should be greatly encouraged. The use of contracting models should also be considered within the framework of new networks.
- Identifying the benefits of renovation plans!
In order to overcome the cost factor involved in sustainable renovation and create acceptance for renovation measures which go further than simple repairs, it makes sense to identify and highlight the benefits. As well as the potential for cutting energy costs, the improvement in housing comfort is an important argument for acceptance of renovation measures.
- Inhibiting factors in the legal framework and current building regulations!
Some of the documented architectonic solutions show that in the rebuilding and renovation of housing estate houses very unconventional plans are also made and large extensions to the living area wanted. These sometimes come up against restrictive local authority building regulations which either do not grant permission for extending the floor space or allow too little scope for the designs of a younger innovative generation.
Local authorities should be recommended to check current housing development plans and local building regulations for such inhibiting factors and remove them.
Financial incentives in the form of grants are basically a central steering instrument for comprehensive renovation. Resource-conserving renovation of the existing housing stock should also be the primary strategy followed by the instrument of grants as opposed to opening up new building land. We see two strategies to follow in order to benefit from the steering effect:
- Grants for energy optimisation of existing buildings and parts of buildings more than 20-25 years old.
- Grants to young families for the maintenance and renovation of an old house rather than building a new one.
- Research: new innovative building solutions!
Aesthetics, improvement in housing comfort and the price, as opposed to considerations about ecological sustainability, are still the decisive factors for the choice of renovation components and measures carried out.
Solutions which are technically simple to implement and materials which combine aesthetic demands, efficiency, workability and a tolerable price level will also be in demand in the future. Because of the high proportion of renovation work carried out by owners themselves, we suppose that prefabricated systems and modules of guaranteed quality which, like dry mortarless construction in interior construction, are easy to handle without professional help have the greatest market potential.
- Demonstration projects!
As already known from experience in the field of new construction, demonstration projects can achieve a certain exemplary effect. Due to its high proportion of housing estate houses in need of renovation, a demonstration project in Lower Austria, especially in southern Lower Austria, could be an important stimulus.
- Info point: Detached House Renovation
In addition to a wide-ranging network of projects and initiatives concerned with implementing sustainable renovation plans, a central info contact point on the theme of the renovation of old detached houses could fulfil an important function in encouraging knowledge-transfer between science and business and the transfer of the available knowledge into construction practice.
Projektgemeinschaft "Neue Standards für alte Häuser"
DI Edeltraud Haselsteiner
Project or cooperation partner
Havel & Havel Beratungs GesmbH
A-3031 Rekawinkel, Hauptstrasse 18
Mag. Margarete Havel
AEE - Arbeitsgemeinschaft ERNEUERBARE ENERGIE NÖ-Wien
Schönbrunner Straße 253/10, A-1120 Wien
Tel.: +43 (1) 7107523
Fax: +43 (1) 7107523 - 18
IBO - Österreichisches Institut für Baubiologie und -ökologie Gmbh
1090 Wien, Alserbachstrasse 5/8
Dipl. Ing. Thomas Zelger
A-3100 St.Pölten, Wiener-Str.54, Stg.A
Bramac Dachsysteme International GmbH
A-3380 Pöchlarn, Bramacstraße 9
Mag. Dieter Usleber
Bausparkasse der Oesterreichischen Sparkassen AG
A-1030 Wien, Beatrixgasse 27
Dipl. Dr. Charlotte Harrer
Landesverband der NÖ - Sparkassen
A-1030 Wien, Grimmelshausengasse 1
Extension and modification concept
Arch. DI Kurt Karhan
Arch. DI Wolfgang Junger
Tel./Fax: +43 1 9834038
Mobil: +43 699-12698082