A Passive House is a structure built according to the rigorous, voluntary Passivhaus standard for energy efficiency in a building, reducing its ecological footprint. It results in ultra-low energy buildings that require little energy for space heating or cooling.
The first passive houses were built in Germany in 1990, but they were inspired by the super-insulated houses built in North America (many in Vermont) during the 1970s and '80s.
Passive houses incorporate the following energy-saving features:
- Compact form and superinsulation
- South-facing windows to gain winter heat, with shading to keep out summer sun
- Minimal thermal bridging—a major avenue for heat loss
- Energy-efficient window glazing and frames (in our case, triple-paned argon-filled windows)
- Tightly-sealed building envelope
- Fresh air ventilation with heat recovery
- Energy-saving household appliances
Before construction, a passive house's energy is carefully predicted using a monstrously complicated spreadsheet called PHPP (Passivhaus Planning Package). The goal is to build something that meets the following requirements:
- The building must be designed to have an annual heating demand as calculated with PHPP of not more than 15 kWh/m² per year (4746 btu/ft² per year) in heating and 15 kWh/m² per year cooling energy OR to be designed with a peak heat load of 10W/m²
- Total primary energy (source energy for electricity and etc.) consumption (primary energy for heating, hot water and electricity) must not be more than 120 kWh/m² per year (3.79 × 104 btu/ft² per year)
- The building must not leak more air than 0.6 times the house volume per hour (n50 ≤ 0.6 / hour) at 50 Pa (N/m²) as tested by a blower door
Tens of thousands of passive houses have been built in Europe, and some municipalities even require them by code. Relatively few have been built or retrofit in North America so far, but there is a fervent Passivhaus community on this side of the Atlantic. We all hope that this kind of construction will eventually become the norm!