Passive Houses do not look any different from other buildings. However, on account of their clearly defined energy standard, they exhibit a high level of thermal comfort and extremely low energy consumption. Good planning as well as careful execution of the details is essential in the construction of Passive House buildings. This ensures that the high requirements for the building envelope and technology can be met.
Buildings meeting the strict Passive House certification criteria can be certified as Passive House buildings
what is passive house?
Passive House (or PassivHaus) was originally developed in Germany and has since spread throughout Europe. The standard continues to evolve and is now finding popularity in diverse climatic regions including California, Japan, Indonesia and Australia. To date 40,000 houses, schools, offices, and other building types have been built to the Passive House standard around the world.
Passive House is fundamentally about design. It is best approached as an integrated design process with the whole design team involved. As a fabric-first construction standard summarised by 5 design principles and performance criteria, it ensures a design delivers very high performance and comfort for the lifetime of the building, pluging the “Performance Gap” often experienced in building operations.
It relies on building physics and carefully integrated, minimal building services and technology. By eliminating the need to bolt expensive additional technology onto a poorly performing building, it eliminates the risk of bolt-on green-bling compromising the architecture.
Special windows and a building shell consisting of highly insulated exterior walls, roof and floor slab keep the desired warmth in the house – or undesirable heat out
Passive House buildings allow for energy savings of up to 90% compared with typical existing buildings and over 75% compared with average new best-practice constructions. Similar energy savings have been demonstrated in warm climates where buildings require more energy for cooling than for heating.
Passive House buildings are also praised for their high level of comfort. They use energy sources inside the building such as the body heat from the residents or solar heat entering the building – making heating a lot easier
A ventilation system consistently supplies fresh air making for superior air quality without causing any unpleasant draughts. A highly efficient heat recovery unit allows for the heat contained in the exhaust air to be re-used.
passive house criteria
Passive House design principles are met via quantifiable Passive House Criteria, a series of minimum performance requirements to achieve certification.
indoor air quality
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
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 /
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
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).