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Passive House Certification is awarded to buildings that reduce energy use from 70%-90% through a super insulated, passive solar, building envelope, and simple mechanical systems. Certifications are issued from the Passive House Institute of the United States (PHIUS). We like to think of the PHIUS approach as relying on physics rather than mechanics, or as Fine Homebuilding called it, “Green without Gizmos.”

The certification can be applied to single family residences, but also to multi-family and dormitory buildings and light commercial buildings like schools and community centers. Watershed provides energy and hygro-thermal modeling to support Passive House design and certification. The modeling is most useful when begun early in the design process and used as a tool to give feedback on different design strategies.

The Principles of Passive Building from the Passive House Alliance and PHIUS:

What is it like to live in a passive house? Can you open the doors and windows?

Passive houses and buildings are extremely comfortable in all seasons. That’s because there are no drafts, temperature variance is extremely narrow (even near doors and windows), and active, balanced ventilation makes for superb indoor air quality. And yes, passive house owners open their doors and windows just as they would in a conventional home. 

Passive buildings are super airtight – what about moisture and mold problems?

Passive buildings do require an extremely airtight building envelope. Combined with super-insulation, this approach dramatically reduces temperature variation, which also prevents condensation and mold issues. The constant, low-level ventilation also helps prevent moisture problems in addition to maintaining excellent air quality.


passive house diagram


passive house institute


passive house