Passive House is voluntary standard for energy-efficiency that results in ultra-low energy use buildings. Buildings constructed under the Passive House standard require very little energy to heat or cool; these buildings are also very comfortable places to live and work. The Passive House standard can be applied to new construction or renovated buildings. Most buildings, built to the Passive House standard, are residential. However, the Passive House standard can be applied to commercial buildings.
Three requirements must be met in order for a building to be (certified) as Passive House:
- Air leakage of the building must be at or below .6ACF50.
- Space heating and cooling demands less than 4.75kBTU/SF/year OR the peak heating load must be is less than 3.17BTU/hour/SF.
- Primary energy use must be less than 38.1kBTU/SF/year.
Only buildings certified as a Passive House can be called a Passive House.
Passive Houses require a balance of solar heat gains, internally produced heat gains, and a small amount of supplemental heat (or cooling) to offset heat loss (or gains) and air-leakage through the thermal envelope (exterior walls, windows, and roofs).
The low supplemental space heating and cooling demands of a Passive House are met by the construction of an exceptionally high quality thermal envelope. This construction is accomplished by enhanced and super-insulation, enhanced air-sealing, and the elimination of thermal bridging. Windows are exceptionally well sealed and insulated; the glazing resists solar radiation.
Because of the requirements for low primary energy use, lighting, appliances, and other electrical uses must be extremely energy-efficient.
Due to air-sealing and the resulting air-barriers found in Passive House construction, mechanical ventilation is needed. Heat recovery ventilators (HRV) or Energy Recovery ventilators (ERV) are used. These ventilation systems provide an adequate supply of fresh air inside the building.
In the United States, a house built to the Passive House standard results in a building that requires space heating energy of 1 BTU per square foot per heating degree day, compared with about 5 to 15 BTUs per square foot per heating degree day for a similar building built to meet the 2003 Model Energy Efficiency Code. This is between 75 and 95% less energy for space heating and cooling than current new buildings that meet today’s US energy efficiency codes.
Currently, there are approximately 15,000 to 20,000 Passive Houses around the world with more being constructed every day.
The image shown above is of a Passive House located in Wales, designed by bere:architects.