Passivhaus Technical Requirements

The table below shows the key technical characteristics of a Passivhaus. The first four must be met in order to achieve the Passivhaus standard. The last two are key criteria in ensuring good internal air quality and high levels of thermal comfort.

Requirement Criterion
1. Airtightness 0.6 air changes per hour at 50Pa (positive and negative) pressure
2. Annual Heat (Cooling) Demand* 15kWh/m².a (kWh per square metre per year needed to provide space heating to 20C, or cooling in hot climates)
3. Maximum Heat (Cooling) Load* 10W/m² (maximum power needed to maintain 20C internally when it is -10C outside)
4. Primary Energy Consumption
120kWh/m².a (kWh per square metre per year needed to meet all energy demands, energy defined as consumed at source, e.g. heat extracted from fuel at power station)
5. Ventilation 30m³ per person per hour (needed to provide fresh, healthy air to building occupants)
6. Minimum Internal Surface Temperature >17C (lower surface temperatures cause convection driven drafts; this target avoids this allowing all parts of the building, even those adjacent to windows to be used)

*either the Annual Heat Demand or Heating Load target must be met.

To achieve these standards, walls, roof and floor - the components that make up the "thermal envelope" - need U-values of 0.15W/m²K or better, depending on the shape (form) of the building - less efficient building forms require higher performing thermal envelopes to achieve the standard. Passivhaus buildings are ‘effectively’ thermal bridge free. This means psi values of less than 0.01W/mK. In new builds this is achievable with careful design; in renovations it is not normally practicable. Windows need overall U-values of 0.80W/m²K (0.85W/m²K installed), along with other characteristics, such as low psi-value spacers, good frame U-values, high g-values (also known as Solar Heat Gain Co-efficient), double all-round gaskets for air-tightness.

Download our pdf for more technical information about Passivhaus.

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