Buildings that have been built to this standard use up to 80% less energy than a conventionally built structure whilst also improving the level of comfort for its occupants and significantly improving the air quality.
Characteristics of a passive house include the following:
- Heavy Insulation: The most important component of a passive house is a layer of highly efficient insulation that wraps continuously around the building envelope — even beneath the concrete slab in the basement — reducing heat transfer between indoor and outdoor spaces
- Design without thermal bridges: The heated air inside a house will follow the path of least resistance to the outside of the house, known as a “thermal bridge.” Conventional homes offer plenty of them, in the form of inefficient windows, poorly insulated walls or cracks under doors, but passive house design eliminates them through superior insulation and efficient windows and doors.
- Airtight construction: Passive houses feature airtight construction to prevent moist room air (or humid outside air, in warmer climates) from penetrating into the home’s construction where it can cause mold, affect inside air quality and even structural damage.
- Ventilation: Another important component of passive house design is its efficient central ventilation system, which continually exchanges moist, “polluted” inside air for fresh, filtered outside air to maintain a comfortable, consistent temperature and humidity level.
- Passive heating technology: Perhaps the most ingenious part of the passive house concept is its ability to heat (or cool) the inside spaces with nothing but fresh exterior air. As fresh, cold air enters the house through the ventilation system, it is heated by the warm air it passes on its way out.
- High-efficiency windows: Efficient windows are essential to the passive house design. The specific windows used vary from climate to climate, but triple-paned windows with low-e glazing, argon gas and insulated frames are common.
- Passive solar gains: Passive solar gain — that is, the good old warmth of the sun — is the primary source of heat for a passive house, so the situation of the home on the lot and the size and position of windows are important factors.
Despite the high standards required for passive house certification, most conventional houses can be remodeled to achieve passive house status by making improvements to the insulation and air tightness, replacing existing windows with high-efficiency windows, and modifying the existing duct work to accommodate the passive house system of heat recovery from exhaust air.