Passive House Criteria
Passive House design principles are met via quantifiable Passive House Criteria, a series of minimum performance requirements to achieve certification.

The absolute indoor air humidity levels do not exceed 12 g/kg for more than 20% of the occupied time. Dehumidification allowance if no cooling plant is proposed.

Airtightness is set at = 0.6 ach (+/- 50 Pascals). Alternatively, air permeability is set at = 0.6m3/hr.m2 (+/- 50 Pascals) for larger buildings. This is a minimum requirement for all Passive Houses, and represents an extremely air tight building with only minimal gaps in the envelope. An air tight building allows more closely controlled environments, with significantly improved thermal comfort (no more draughts!).

The air temperature must not exceed 25°C for more than 10% of the occupied time to ensure that comfortable temperatures are achieved during the hot summer months.

Annual space cooling/dehumidification demand is set at = 15kWh/m2.yr. Alternatively, space cooling load is set at 10W/m2. This represents the demand on the cooling system to maintain a consistent comfortable temperature throughout the year. It is a function of the building fabric thermal performance, the air permeability and the outside air ventilation required for maintaining indoor air quality. It is also independent of the proposed mechanical plant efficiencies.

Annual space heating demand is set at = 15kWh/m2.yr. Alternatively space heating load is set at 10W/m2. This represents the demand on the heating system to maintain a consistent comfortable temperature throughout the year. It is a function of the building fabric thermal performance, the air permeability and the outside air ventilation required for maintaining indoor air quality. It is independent of the proposed mechanical plant efficiencies.

Annual primary energy demand is set at = 120kWh/m2.yr. Alternatively with renewables, it is set at = 60kWh/m2.yr. This is the predicted total energy demand of the building, including heating, cooling, hot water generation, ventilation, lighting and equipment loads. It takes into consideration the efficiencies of mechanical plant and any renewable generation (if proposed).