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Green Building Technology in Austria: State of the Art and Prospects

bridges vol. 11, September 2006 / Green Buildings Focus
by Martin Treberspurg & Roman Smutny

The path to a sustainable future
The goal of Sustainable Development is to meet the needs of the present generation without compromising the ability of future generations to meet their own needs. This means that we have to provide enough energy and material resources for the next generations, an objective that can by achieved by two parallel measures: increasing our resource efficiency and transitioning to renewable resources.


The figure shows the total primary energy demand of the EU. The "Negajoules" band on top indicates the energy being saved by efficiency measures, based on 1971 energy usage. The basic message is: The energy demand is rising, and without efficiency measures the increase would be even higher. In spite of remarkable energy savings by efficiency measures, the total demand has not been reduced. Due to the pressure of an increasing energy demand a significant transition to renewable resources has not yet occurred and is likely to be marginal further on. If we wish to provide energy resources for future generations, the measures have to be deeply intensified. This is also of particular importance for the protection of the climate.


{access view=guest}Access to the full article is free, but requires you to register. Registration is simple and quick - all we need is your name and a valid e-mail address. We appreciate your interest in bridges.{/access} {access view=!guest} How do building activities influence Sustainable Development?

Buildings are of crucial importance for social and environment related politics. On the one hand, we spend about 93 percent of our time in buildings. On the other hand, the life cycle of building construction has an important impact on the environmental performance of a region. Buildings in Central Europe cause: -

  • nearly the half of the primary energy demand
  • nearly the half of the greenhouse gas emissions
  • approx. 25 percent of the mineral material demand
  • approx. 60 percent of the annual waste production.

Due to their long lifespan, most buildings have long-term impacts on the environment and on future generations. Responsible architecture seeks to significantly reduce the total energy demand of buildings, which is feasible with innovative building technology. A passive house requires only 10 percent of the heating energy of an average Austrian house. Meanwhile, more than 1000 new buildings in Austria meet the Passive House Standard and existing buildings can be refurbished to reach the Passive House Standard, as demonstrated by pilot projects.

Passive house standards
A passive house is a super-insulated green building with a comfortable and healthy interior climate that can be maintained without active heating and cooling systems. Thermal comfort can be achieved exclusively by post-heating or post-cooling of the fresh air mass required for adequate indoor air quality. Hence, an efficient ventilation system, already needed in energy efficient and airtight buildings, is sufficient to heat and cool the building.

Ventilation systems of passive houses are very different from air-based heating and cooling systems used in America. Air conditioning systems mainly recirculate indoor air at a very high rate (> 10 air changes per hour (ach)). In passive houses, the air is not recirculated but is replaced by external air to maintain good air quality (0.3 to 0.6 ach).

A common misunderstanding is the fear that the windows in passive houses cannot be opened. Of course they can, but they don't need to open, because fresh air is continuously supplied via the ventilating system. Unlike window ventilation, fine filters in the ventilating system keep out dust and pollen. Hence, a passive house enables greater comfort, especially for people sensitive to dust, allergens, or traffic noise.

The passive house concept was developed in the late '80s by Prof. Bo Adamson from Lund University in Sweden and by the German physicist Wolfgang Feist, founder of the Passive House Institute in Darmstadt. The concept could be implemented at this time because of the new development of energy efficient windows. The first passive house was built in 1991 in Darmstadt, Germany.

The passive house concept is not a construction method or a building style. It is a building standard, that is defined by a heating load of less than 10 W/m² or 3.17 Btu/(hr.ft²) per net residential area. This limiting value is derived from the maximal temperature of preheated fresh air of 122°F (to avoid smoldering of dust). The annual heating demand in a passive house depends on the climate. In Austria typically 15 kWh/(m².a) or 4755 Btu/(ft².yr) are needed per net residential area. In Stockholm this value could be as much as 20 kWh/(m².a) or 3170 Btu/(ft².yr), and in Rome perhaps 10 kWh/(m².a) or 6340 Btu/(ft².yr).

To achieve the passive house criteria, three major aspects must be considered: super-insulated building envelope, airtight building, and solar inputs. Thus, a precondition for energy efficient buildings is a sophisticated building envelope.



A further requirement for passive houses is an airtight envelope to avoid thermal losses. The air change rate through unsealed joints must be less than 0.6 times the house volume per hour at a pressure difference of 50 Pa (375 mTorr; 0.00725 psi). The European CEPHEUS project has analyzed living quality, environmental performance, and construction costs of 114 passive treberspurg_schiestlhaus_smallhouses. Average energy savings of 90 percent compared to existing conventional buildings was confirmed. The research project showed that average additional costs of 8 percent occurred for constructing the first passive houses. It can be concluded that passive houses are economically reasonable due to decreased operating costs, higher thermal comfort, and healthier indoor air conditions.
The passive house concept is practicable for all kinds of buildings. In Austria, many passive residential buildings and office buildings are already in use, as well as several examples of other buildings: administration buildings, schools, kindergartens, student residence halls, and supermarkets. An attractive example of a passive house in an extremely cold climate is the Schiestlhaus in the Austrian Hochschwab region. This Alpine refuge is located 2154 m (7067 ft) above sea level in an "island location" and was designed to be self-sufficient and eco-friendly with respect to energy and water usage.

The role of Austria in technology transfer and the diffusion of passive housing





During recent decades, Austria has accumulated substantial practical experience concerning passive houses, solar heating systems, and biomass energy production systems, and has been a pioneer in the diffusion of eco-friendly and energy efficient houses. Currently, it can claim twice as many sustainable settlements per resident as Germany (Source: http://sustainable-settlements.net). The following figure shows the development of passive houses in Austria. In the last three years, the total floor area has doubled each year. Meanwhile, Austria has the highest number of passive houses per resident worldwide.



Currently the largest passive housing estate in Austria with 114 dwellings is near completion (see following figure).



A passive house can be designed in different ways. Austrian passive houses have been built in light-frame timber construction, in massive timber construction, and in massive construction with concrete or bricks. There are also some examples of refurbishing existing buildings into passive houses. The renovation of Makartstrasse, a 50 unit housing estate in Linz, used a super-insulated passive solar façade and decentralized ventilation systems. This resulted in 90 percent savings in heating energy and operational costs. It is obvious, that Austria currently has a lot of diversified planning expertise in the field of passive houses which can be a valuable resource for foreign architects, building engineers, and planners of building services.

On the subject of building services, let me briefly introduce two Austrian success stories: Austria currently has the highest rate of solar collectors per resident in Europe (besides Cyprus). The total area of installed solar collectors is 3.1 million m² (33 million ft²) and is increasing by approximately 0.2 million m² per year (0.22 million ft²). To grasp these figures, let's compare with Australia. Even with Austria's much smaller population and less solar radiation, the annual sales of glazed solar collectors are 50 percent higher than in Australia. This is also an important factor for the economy: More jobs are generated by the solar heating industry than by the Austrian ski producers.

Solar heating concepts have been optimized by simulation with TRNSYS and successfully tested in practice. Online monitoring of solar systems has proved to be valuable for owners and occupants, providing safeguards against failure and malfunction and helping to adjust the control settings and thereby increase solar gains. Experience and planning competence are available especially for large volume houses - housing estates, office buildings, hotels, and business/industrial facilities.

The second success story concerns biomass heating. About 43 percent of the land area in Austria is forested. Biomass resources are used from forestry, agriculture, and the food industry and timber industries. Since biomass heating has been continuously supported, the regional economy has been strengthened. Meanwhile, Austria is the technology leader in the production of boilers for split logs, wood chips, and pellets.

Why does green building work well in Austria?

The housing subsidy scheme: High income taxes (30-40 percent) in Austria enable several steering mechanisms. About 1.3 percent of the gross domestic product is used for housing subsidies. This stabilizes the building industry and has positive impact on social integration, the overall quality of buildings, and especially the ecological building performance. In early 2006, the housing subsidy scheme in the federal state Vorarlberg was revised. Passive House Standards are now mandatory for subsidized housing estates. As of October 1, 2006, a solar heating system is mandatory for subsidized housing estates in the federal state Styria.

  • Building laws with mandatory values for thermal insulation (see previous table). Thermal resistance limits for the building envelope have been increased several times during recent decades.
  • A law banning nuclear power plants (Atomsperrgesetz, BGBl. Nr. 676/1978). The use of nuclear fission as an energy supply was prohibited after a plebiscite in 1978. This has been an early success on the road to a sustainable energy supply.
  • Individual initiatives: The passive house movement started in the federal state Vorarlberg because of the commitment of individuals. Vorarlberg still has the highest density of passive houses. A similar story but concerning solar heating systems has happended in Styria. Individuals who provided guidance in building the first solar collectors for private homes formed the AEE INTEC, now one of the leading R&D companies for solar heating systems. Meanwhile there are several housing developers in Austria who build each new housing estate with a solar thermal system and tend to build passive housing estates only.
  • Funding of research and development: The BMVIT-program on "technologies for sustainable development" (at:sd) has a focus on the "Building of Tomorrow" and has supported approximately 200 projects (see the article by Mr. Paula and Mr. Bauer in bridges Vol. 8, Dec. 2005. Core projects of the initiating program are innovative building and reconstruction concepts and their realization. Several demonstration buildings already draw international interest. A further support program, klima:aktiv, aims at educating and assisting planners and builders as well as implementing existing know-how.
  • Energy performance certificate for buildings: Documentation of the planned energy performance is mandatory for new buildings since the '90s in some parts of Austria. With the implementation of the European Directive for the energy performance of buildings (EPBD, Directive, 2002/91/EC) an energy certificate will be mandatory for new and existing buildings. The deadline for full implementation is January 1, 2009. The certificate includes key figures for energy flows and characteristics of the building service equipment, comparable to a technical certificate for a car or a PC. This will be an important source of information for residents and investors. Furthermore, it is expected that this information will be integrated into the calculation of the market value of buildings, which is not yet the case. Currently the calculated market value of passive houses is no higher than that of conventional houses.


  • Currently an EU-Directive on the resource efficiency of buildings is being drawn up, and the European Committee for Standardization (CEN) is commissioned to prepare the relevant standards. It is expected that this directive will lead to an upgrade of the energy certificate into a resource certificate for buildings.
  • Product stewardship: The International Union of Architects (UIA) has set up a list of criteria to promote the spread of sustainable buildings. One issue was the liability of building developers and owners of a building. If they take on this responsibility, they must provide plans and instructions for disassembling the building and recycling the building materials. An estimation of the costs is also needed. These documents, together with necessary funds, should be provided before completion of the building. This idea is not feasible at present, but other initiatives are working in the same direction: Product stewardship is consistent with the aim of the EU initiative for Integrated Product Policy (IPP), which has identified housing as one of the products with the greatest potential for environmental improvement.
  • Ecological building materials: It is expected that the use of sustainable building materials will increase. Austria's best practice example for the use of straw is the "S-house" in Böheimkirchen (prizes: Global 100 ECO-TECH Award, see: http://www.s-house.at) and for the use of loam and adobe, the "Lehm-Passivhaus" in Tattendorf.
  • Ecological building refurbishment: There is a vast potential for the thermal renovation of building envelopes. Savings of up to 90 percent in energy and operating costs are possible.
  • Currently there is extremely low public demand for sustainable buildings. It is likely that the demand for a higher living comfort will raise the demand for passive houses. This will be supported by increasing prices for fossil fuels. Presumably the prices will continue to rise as fossil resources become scarce. Prof. Kenneth Deffeys of Princeton University claimed that the world's peak oil production already occurred early in 2006. From this date on, oil production will decrease, first slowly and then more and more quickly.
  • The atmosphere has served as a free "sanitary landfill" for greenhouse gas emissions. The follow-up costs of this "dumping" are not assigned to the polluter. Political steering instruments to reduce greenhouse gas emissions are starting to show (small) effects (e.g., the Kyoto protocol) but still must be improved and implemented all over the world. The planned California Act to cut greenhouse gases will be an important step in this direction.


    The authors: Martin Treberspurg is professor for sustainable constructions at the University of Natural Resources and Applied Life Sciences in Vienna and director of the architecture company Treberspurg & Partner Architekten ZT GesmbH. Roman Smutny graduated in civil engineering at the Vienna University of Technology (TU Wien), worked several years in architecture and engineering offices, and has been scientific assistant to professor of architecture Treberspurg since 2005.


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