Passive houses reap ‘Factor 10’ efficiency

The Passive House concept has demonstrated the ability to cut energy requirements by 90%, for only 10% in additional building costs. In view of the large share of energy use and climate emissions that buildings and houses are responsible for, this is a vital innovation. The western Austrian region of Vorarlberg has led efforts for implementation of passive housing through incentives and requirements.



Keywords: passive house, energy demand, super-insulation, heat recovery, passive solar gain

A large share of a society’s total energy use is for heating and cooling buildings. In Europe, the building sector is responsible for about 40% of total primary energy consumption (see also Berlin and Seattle). This makes passive housing important for sustainability, as it reduces energy demand in the built environment.

For example, in Germany, annual heating energy input of 220 kWh/sq m is needed for the building stock, 70 kWh/sq m for new housing, but only 15 kWh/sq m for passive houses. This represents an actual realisation of the Factor 10 goal for resource-efficiency improvement.

Passive housing requires extra costs of only 10% of total building costs, according to one published study – and these must be viewed together with the lower operating costs of housing that does not require artificial external heating. Passive housing uses mechanical ventilation with a highly insulated and airtight building envelope to provide a comfortable indoor atmosphere over the entire year without a separate heating system, therefore the design is termed passive.

Beacon for passive houses
The western Austrian region of Vorarlberg, population 0.4 million, is listed among the world’s leading “beacon” regions for the implementation of passive houses. It clearly stands out as first among these regions for the extent of its implementation. As of 2011, it had more than 60 multi-family buildings and nearly 20 public buildings, for a total floor area of nearly 150,000 sq m. Vienna comes second with nearly 90,000 sq m.

Vorarlberg promotes passive housing through multiple strategies – ranging from incentives to legal requirements. One report quotes a subsidy for new passive housing of €300 per sq m, totalling 24% of the different funding sources for passive housing in 2008. Vorarlberg has also made the passive-house standard mandatory for publicly-funded housing for social purposes. Climate change is a key driver for policy, with an area goal of 100% energy autonomy using only renewables, before 2050.

No heating necessary
The concept is to reduce heat losses to the point where internal and solar gains make it unnecessary to have a separate heating system. Thus thermal insulation of exterior building elements, i.e. superinsulation, heat recovery, and passive solar gain are the three basic elements (see also Sutton).

The world's first passive house was built in 1990-91 in Darmstadt, Germany. Results were positive not only for energy efficiency but also for user satisfaction and air quality, due to controlled ventilation. Darmstadt’s positive experience led to larger scale promotion and policy-adoption of the technology in Europe – for example, the EU-funded demonstration project CEPHEUS (Cost Efficient Passive Houses as European Standards).


References
Jürgen Schnieders, Andreas Hermelink, “CEPHEUS results: measurements and occupants’ satisfaction provide evidence for Passive Houses being an option for sustainable building,” Energy Policy, 34 (2006) 151–171

LANG consulting, 2011, “Passive House beacon regions”, Vienna

Energy Institute Vorarlberg, 2010, “Vorarlberg on the way to energy autonomie”, presentation Vancouver, 23th march

E. Mlecnik, H. Kaan, G. Hodgson, “Certification of Passive Houses: a Western European Overview”, PLEA 2008 – 25th Conference on Passive and Low Energy Architecture, Dublin, 22nd to 24th October 2008

European Commission, no date, “Green Living”, http://ec.europa.eu/clima/sites/campaign/news/news15_en.htm

City Population, http://www.citypopulation.de/php/austria-vorarlberg.php

Text by: Aaron Thomas