Performance Standards: Passive House Institute US
The Passive House Institute US (PHIUS) is a 501c(3) nonprofit organization that provides training, education, and research to promote implementation of Passive House Building Energy standard, as well as the design approach and techniques to accomplish that standard. PHIUS engages in:
- Constructing, measuring, and verifying performance of Passive Houses in all US climate zones
- Conducting nationwide training and certification of Passive House Consultants
- Contributing to the development of minimized mechanical systems for heating, cooling, and dehumidification
- Creating design guidelines for Passive Houses in all climate zones
- Providing energy calculation and consulting services
- Participating in presentations, meetings, conferences, etc. regarding passive construction
The Passive House design concept is a comprehensive system of receiving and retaining energy. A Passive House is designed to be highly-insulated and air-tight, and is primarily heated by passive solar gain and internal gains from people and equipment. Energy losses are minimal.
The window U-value recommendation for a Passive House is ≤0.8 W/m2/K (≤0.14 Btu/hr-sf-°F). A U-factor of 0.14 is very low in the current U.S. market and may be hard to find a window that achieves this low value. This low U-factor is not a Passive House requirement, it is only a recommendation. Passive House designers may use a window with a higher U-factor (0.17–0.20 Btu/hr-sf-°F) and make up the difference in overall house energy performance with additional insulation.
The window Solar Heat Gain Coefficient (SHGC) is another important component in Passive House design. A Passive House is designed to typically meet 50% or more of the heat demand through passive solar gain (another 15–30% is provided by internal gains, leaving less than 20% of the total heating demand to be met by the heating system). This passive solar gain requires that south-facing windows have a high SHGC. It can be very difficult to build a certified Passive House with windows that have a SHGC of less than 0.50. Currently, in the U.S. and Canada, it is difficult to find a window with a SHGC higher than 0.45. Some windows from Europe are certified for use in Passive House design and have a SHGC of 0.60 or higher.
Orientation and shading are key components to Passive House design. Passive House design methodology often results in large window areas on the south facade, with minimal amounts of windows on the east, west, and especially the north facade.
PHIUS Certified Data for Window Performance Program
PHIUS has a Window Performance Program which lists performance requirements for windows in the various climate zones. The program also has window manufacturers submit their certified performance data and that information is listed where you can find and compare products.
Visit the PHIUS web site for more information on Passive House Building Energy standard, training, certification, and much more.