Dr Stephen Ball explains PassivHaus

What is PassivHaus?
PassivHaus is an internationally recognised and proven low energy design standard for both domestic and non-domestic buildings. The principles were developed in Germany in the 1990’s and encompass basic key features like a super-insulated, super-airtight building envelope, southerly orientation to promote useful solar gain, triple glazed windows throughout and a highly efficient mechanical ventilation heat recovery (MVHR) system.

The criteria for compliance with the PassivHaus Standard are:

Heating energy demand 15kWh/m² per year


Building heating load 10W/m²

Useful cooling demand 15kWh/m² per year

Primary energy demand 120kWh/m² per year

Air tightness 0.6/h (leakage less than 0.6 times the building volume per hour @ 50 Pascals)

Excess temperature frequency 10% of the year above 25°C

Is PassivHaus design popular?
There are some 10,000 or so PassivHaus standard buildings throughout the world, but only a handful in the UK. PassivHaus buildings can reduce the energy consumption for space heating by as much as 90% when compared to the average existing stock; helping stave off spiralling fuel costs.
What U-values are typical for a PassivHaus?
Envelope U-values for walls, roof and ground: U 0.15W/(m²K) or better

U-values for tripled glazed windows including the frame: U 0.8W/(m²K) or better

What is the PassivHaus Planning Package?
The PassivHaus Planning Package (PHPP) is a design and verification spreadsheet tool especially adapted to high performance buildings. It is used to verify PassivHaus requirements in terms of the space heating demand, primary energy demand and overheating criteria.
Can you open the windows in a PassivHaus building?
The simple answer is ‘Yes’, but in practice, most occupants choose to keep the windows closed in the winter to maintain the high levels of comfort and air quality delivered via the mechanical ventilation heat recovery (MVHR) system.