A Passivhaus (or Passive House) takes into account the free heat gained from the sun and “internal heat gains” from people and appliances. It is a very well-insulated, virtually air-tight building. Avoidance of heat gain through shading and window orientation also helps to limit any cooling load. A Passive House is a comprehensive system. Working with natural resources, free solar energy is captured and applied efficiently, instead of relying predominantly on ‘active’ systems to bring a building to ‘zero’ energy. High performance triple-glazed windows, super-insulation, an airtight building envelope, limitation of thermal bridging and balanced energy recovery ventilation make possible extraordinary reductions in energy use and carbon emission.
The Passive House System was developed in Germany, where it is called “Passivhaus”, in 1996 by physicist Wolfgang Feist. Feist was influenced by the groundbreaking, superinsulated houses that were built in the US and Canada in the 1970’s. His cause was championed by German born Katrin Klingenberg, who founded PHIUS – Passive House Institute United States.
Benefits of passivhaus building
Improved indoor air quality
Increased physical comfort
90% energy reduction
Minimal conventional heating system
Suitable for retrofits
The point of passivhaus construction is to minimize energy loss by restricting airflow into and out of the building. The building stays warm in winter and cool in summer. Style does not matter, as long as the efficiency and air circulation goals are achieved.
The envelope is super-insulated, up to 16″ beneath the slab and in exterior walls (R 60-70). Strawbale, SIPs and ICFs (insulated concrete forms) or Rastra are suitable. Ceiling insulation of dense-pack fiberglass, cellulose or spray foam has an R-value anywhere between R 60-100.
The triple-glazed windows have a very low U-factor of 0.14. Some in Germany are as low as 0.17. The U-factor rating of the National Fenestration Rating Council (NFRC): the lower the number, the more efficient the window, based on the glass, frame and spacer material.
Thermal bridging is essentially eliminated. A blower door test is run several times during construction to test for air leakage before the building is completely closed up and finished.
A heat recovery ventilator (HRV) keeps indoor air fresh, exchanging indoor air with outdoor air with minimal heat loss.
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