Cost-efficient reduction of the total energy consumption (for space heating, domestic hot water and household electricity) of new residential buildings by at least 75% to a level of no more than 42 kWh/ (m²a). This can be achieved without adding new active components to the building. Instead, the heat requirement is reduced to such a low level that a comfortable interior climate can be achieved both in winter and summer without a separate heating or air-conditioning system. The energy demand for domestic hot water and household appliances is also extremely reduced. Thus, the capitalized costs (investments in the building incl. planning and building services plus running costs over a period of 30 years) of the building are not higher than in an average new building. Passive houses shall be introduced as a new building standard to the European marketplace. This standard creates the basis to cover the remaining energy requirement totally by renewables.
As the project is just about to begin, not many results are available yet. However, it has already been found in all projects that houses built to passive house standards can certainly be marketed, despite partially unfavourable framework conditions. Where difficulties in marketing or delays or modifications of individual projects have arisen, this was generally not due to the required passive house standard but other circumstances. The calculations of the Passive House Institute carried out until now show that the passive house standard will be achieved in all projects.
Passive houses are buildings in which a high level of comfort can be achieved in winter and in summer without a separate heating or air-conditioning system- the house 'heats' and 'cools' itself purely 'passively'. In a passive house, a combination of largely passive techniques is employed to keep the interior climate comfortable. In detail, these are :
- Building fabric : Superinsulated, U-values less 0.15 W/(m²K)
- Building element connections: Reduced thermal bridges, Phi less than 0.01 W/(mK)
- Airtightness : Closed building fabric, n50 less 0.6 ac/h
- Subsoil heat exchanger: Passive preheating of supply air to about 8°C
- Hygienic ventilation: Directed air flow through the whole building, total between 60-140 m³/(h dwelling unit), exhaust air extracted from damp rooms
- Heat recovery: Counterflow air-to-air heat exchanger, efficiency above 80%
- Latent heat recovery from exhaust air: Compact heat pump unit for water heating with a max. heat load of 1 kW, annual COP above 3, monovalent space and water heating system
- Passive utilization of solar energy: Optimized glazed areas that cover approx. 40% of space heat requirement.
- Superglazing: 3-pane low-emissivity glazing, U-value below 0.7 W/(m²K), g-value above 50%
- Superframes : Superinsulated window frames, Uwin for whole window below 0.85 W/(m²K)
- Solar flat plate collectors : about 50% coverage of water heating
- Household appliances : High efficiency low-energy household appliances, savings of over 50%
- Supply of remaining energy demand from renewable sources (only Hannover-Kronsberg): Share in wind power facility, 100% demand coverage over annual average.
This approache has been demonstrated to be theoretically as well as practically feasible: Computer simulation shows that the concept works in European latitudes. The first passive house was built in 1991 in Kranichstein, a district of the city of Darmstadt, Germany. The house is occupied by four families since October 1991. It requires so little 'stand-by heat' for space heating (less than the equivalent of 160 m³ natural gas per year for a dwellling with 156 m³ living area) that it was indeed found possible to dispense with a dedicated heating system.
The cost-efficient passive house approach pursued here is able to deliver a drastic reduction of energy demand while the capitalized costs over 30 years are not higher than for conventional buildings. We thus take the view that here, for the first time, a basis is created for covering the supplementary energy demand by renewables in a manner that is largely CO2-free and is duplicable from both resource and financial cost aspects.
It is intended to demonstrate that, by a combination of the above technologies, this drastic and cost-efficient reduction in energy demand can actually be achieved at different building sites with different climates in Europe. For that, 262 dwellings in cost-efficient passive houses shall be built in 5 European countries (AT, CH, DE, FR, SE). One of the construction sites is situated in the immediate vicinity of the EXPO2000 World Fair and is registred as officially EXPO2000 project. Monitoring of the projects and dissemination of the results are part of the project.
The results of the CEPEHEUS-project shall be presentated at the EXPO2000.