Sustainability-Monitoring of selected Passive Housing Estates in Vienna (Project NaMAP)

For the first time an interdisciplinary building-monitoring according to the concept of a sustainable development was performed. Do Passive-houses achieve the ambitious planning objectives? How much measured energy can be saved compared with conventional housing estates? And what about user satisfaction and construction costs compared with conventional housing estates?

These questions have been posed by the Division of Sustainable Construction of the University of Natural Resources and Applied Life Sciences under the direction of Univ. Prof. Architect Dr. Martin Treberspurg. Interdisciplinary support came from the environmental psychologist Prof. Dr. Alexander Keul of the University Salzburg and Mag. Andreas Oberhuber and his team of FGW Vienna.

The energy performance according to EN 15603 was analysed for all Passive housing estates in Vienna that are occupied more than one year. A comparison was drawn with selected housing estates of the same construction period 2005-2007 that already fulfil Low-Energy-House-standard. The study covers 1367 dwellings, thereof 492 dwellings in Passive-house-standard.

Energy analysis (BOKU Vienna)

Space heating

The actual indoor air temperature in dwellings during the heating period is about 22 °C - 24 °C according to measurements of AEE INTEC. The useful heating energy demand was re-calculated for 23 °C.

The measured consumption values correspond very well with the calculated values for 23 °C.

The annual energy consumption of Passive-Houses is 17 kWh district heating per gross floor area. About 30 kWh or two-thirds of energy are saved compared with conventional housing estates of the same construction period.

Equipment losses have to be taken into account and are so far underestimated for Passive-Houses.

Heating and hot water

Younger housing estates generally consume less heating energy. Between 1985 - 2005, the reduction of district heating was about 20 kWh/(m².a). Referring to 2006, the Passive-House-standard saves about 30 kWh/(m².a). For households, this means savings of about 2.5 MWh, 230 € (price of September 2009) and 500 kg of greenhouse gases per year.

Compared to conventional building, Passive-Houses have a more balanced energy consumption throughout a year, which is favourable for the supply of district heating. This also causes lower greenhouse gas factors in case of a monthly calculation. A more efficient utilization of district heating in Passive-Houses can be achieved by larger heaters.

The annual greenhouse gas emissions of Passive-Houses are approx. 8 kg CO2-equivalent per m² and not dependent on the energy carrier (district heating, gas, electricity). The major energy flow of new Low-Energy-Houses are transmission losses. The Passive-House-concept effectively reduces this energy flow by 23 kWh/(m².a). Further energy savings of 10-15 kWh/(m².a) can be achieved by optimised equipment for heating and hot water. About 10 kWh/(m².a) energy savings have been documented for solar thermal installations. Even higher yields are possible for solar space heating with large-scale collectors. Heat recovery from waste water enables minor extra savings.

Cost analysis (FGW Vienna, A. Oberhuber, B. Schuster; BOKU Vienna, R. Smutny)

The first generation of housing estates in Passive-house quality generated 4% - 12% higher construction costs compared to low-energy houses. Higher values have been noticed for the first buildings with decentralized ventilation systems. Central ventilation systems caused only small additional costs of 4% - 6%. Meanwhile, the costs for decentralized ventilation systems are on the same level as for central systems. The additional costs for future Passive housing estates are estimated to be around 4% - 6%. This level has also been reached by the Sophienhof in Frankfurt and the Lodenareal in Innsbruck.

The costs for Passive-house windows are currently about 25% higher than for conventional windows. Due to further diffusion of Passive-houses and the development of innovative components (e.g. vacuum windows) price reductions are possible.

For all investigated Passive- and low-energy-houses a major increase in construction costs was detected with decreasing floor area as well as with decreasing compactness of the building. Housing estates with less than 2000 m² useful floor area cause about 10% - 20% additional costs. Less compact housing estates cause about 15% - 25% additional costs.

Subsidized residential buildings receive a state loan with a fixed interest rate of 1 % and a duration of 35 years. During the first 15 years the maximal increase of rents is limited by law. After the 15th year the rents could increase dynamically in order to pay-back higher construction costs. The new Viennese Passive-house subsidy prevents this dynamical rent increase by means of a direct payment of 60 €/m² and therefore plays an important role for intergenerational Sustainability.

A post-occupancy-analysis of housing statisfaction (Uni Salzburg, A. Keul)

Housing satisfaction was assessed by post-occupancy evaluations (POEs) in six newly-built estates in 2007/08. A questionnaire covered sociodemography, well-being, attraction, housing quality indicators, improvement wishes, passive housing knowledge, motivation to save energy and information on problems with heating/ventilation. A POE series reached 399 new flats and 225 of them returned data (56%). A comparison with conventional housing (156 flats/houses) was also done.

5 of 6 passive housing estates show a high tenant satisfaction (3 even at the level of detached single housing), 1 was on conventional level (with a reported improvement 2008/09).

Flats were mostly not selected because of energy standard; the tenants being no "green party" population. Problems were noticeable in the technical regulation and adaptation phase after moving in. Written Passive housing information was rated good, but has potential for improvement. A short "operating instruction" or "checklist" would be helpful.

Passive housing has passed the Austrian "mainstream test" with success. Everyday passive housing acceptance needs well-being, technical briefings and good service.

Conclusion

Passive-house-standard for subsidized housing estates has several advantages compared with conventional buildings: Living comfort, energy efficiency, climate protection and energy costs.

The higher indoor air quality in Passive-Houses requires additional electricity, which is not noticeable in Passive-Houses with highest ventilation efficiency. The total energy consumption of all measured Passive-Houses is clearly lower than in Low-Energy-Houses. Passive-House standard is the basis for energy efficient construction. Further considerable contributions can be achieved by efficient building equipment and active solar energy utilization. For the heat distribution system, it is recommended to use insulation with a thickness of twice the diameter of the pipe.

Passive-Houses cause important indirect contributions for climate protection due to learning effects for thermal refurbishment to Passive-House-standard. Dedicated refurbishments together with switching from gas to district heating have considerable long-term effects for climate protection.

New buildings should be constructed in Passive-House-Standard, otherwise they will become objects for refurbishment in the future which will result in higher life-cycle costs. Energy monitoring is not just quality assurance but also fine-tuning and increase of energy efficiency.

The cooperation with socio-scientific analysis provides synergy effects and delivers new knowledge for developers, planners, energy suppliers and administration. The findings of this project are transferred into a Passive-house-academy. Obligatory monitoring for all subsidized buildings is suggested, as well as a publicly visible information board for the final energy demand.
Facts
  • Project Management
    University of Natural Resources and Applied Life Sciences, Vienna
    Institute of Structural Engineering (IKI)
    Division of Sustainable Construction
  • Project Team
    Martin Treberspurg
    Roman Smutny
    Ulla Ertl-Balga
    Roman Grünner
    Christoph Neururer
  • Projektpartner
    Uni Salzburg: Alexander Keul
    FGW: Birgit Schuster, Andreas Oberhuber, Kerstin Götzl
    WU-Vienna: Philipp Kaufmann
  • Duration
    January to December 2009
  • Contact
    martin.trebersburg[at]boku.ac.at
    roman.smutny[at]boku.ac.at
  • Downloads
  • Abstract 1.1 MB
    Project report 6.45 MB german only