What is Passivhaus?
Passivhaus or 'Passive House' is the fastest growing energy performance standard in the world with 30,000 buildings realised to date with the majority of those since the turn of the century. The Passivhaus standards strengths lie in the simplicity of its approach; build a house that has an excellent thermal performance, exceptional airtightness with mechanical ventilation!
This robust approach to building design allows the designer to minimise the 'Heating Demand' of the building and in some residential buildings only specify a heated towel rail as means of conventional heating, this heat can then be recovered and circulated by a Mechanical Ventilation and Heat Recovery (MVHR) unit.
The Standards Origins
The Passivhaus standard was developed in Germany in the early 1990s by Professors Bo Adamson of Sweden and Wolfgang Feist of Germany and the first dwellings to be completed to the Passivhaus Standard were constructed in Darmstadt in 1991.
The Passivhaus standard can be applied not only to residential dwellings but also to commercial, industrial and public buildings.
This has led to the following functional definition of a Passivhaus.
“A Passivhaus is a building, for which thermal comfort can be achieved solely by post-heating or post-cooling of the fresh air mass, which is required to achieve sufficient indoor air quality conditions – without the need for additional recirculation of air.”
...meaning the heating requirement in a Passivhaus is reduced to the point where a traditional heating system is no longer considered essential. Cooling is also minimised by the same principles and through the use of shading and in some cases via the pre-cooling of the supply air. Night purging and the use of natural cross-ventilation through open windows is encouraged during the summer months.
As well as being an energy performance standard Passivhaus also provides excellent indoor air quality, this is achieved by reducing the air infiltration rates and supplying fresh air which is filtered and post heated by the MVHR unit.
The Passivhaus standard can be applied to any climate in the world and works equally as well in warm climates as it does in more moderate climates. To date Passivhaus buildings have been designed and built in every European country, Australia, China, Japan, Canada the USA and South America....a research station has even been constructed to the Passivhaus standard in Antarctica!
As we become more aware of fuel poverty it becomes increasingly important to reduce our dependence on fossil fuels, with fuel prices continuing to rise the low heating demand of Passivhaus Buildings of less than 15kWh per square metre per year means that annual fuel costs are reduced by a factor of 5-10. For example a household living in a 70m2 Passivhaus with gas heating could spend as little as £25 on space heating each year.
For more information on the Passivhaus standard please view BRE's interview with Dr. Wolfgang Feist here