The Passivhaus Definition
Passivhaus is a standard for housing design developed by Professor Wolfgang Feist of the Passivhaus Institute in Germany. The passivhaus standard sets out a way to reduce energy use for space heating and cooling by 90% compared to a traditional build house, which on average uses around 110kWh/m2/yr.
The principle is defined as the total energy demand for space heating and cooling, and this must be less than 15kWh/m2/yr of treated floor area to earn passivhaus (PH) certification.
- Super air-tight envelope (<0.6ach)
- Minimal cold bridging in the external frame
- Controlled internal air quality by mechanical ventilation system
- Clever design of solar gain and summer shading to maximise winter heat gain from the sun.
- Use of low energy household appliances and lighting.
As well as this, the total primary energy use for all appliances, domestic hot water and space heating and cooling must be no greater than than 120 kWh/m2/yr.
In 2015 the Passivhaus institute introduced two further levels of passivhaus certification for build efficiency:
A Passivhaus plus home (PH+) must not require more than 45 kWh / (m²a) of renewable primary energy. In addition, it must generate at least 60 kWh / (m²a) of energy, based on the surface area, and Passivhaus premium where by the energy requirement is further limited to 30 kWh / (m²a), the energy generation must be at least 120 kWh / (m²a).
At present (April 2017) there are only four homes built in the UK that have achieved formal Passivhaus + certification, our own Weyhill project in Hampshire being among them!