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What is Passive House?
There are a lot of terms out there in the world of green building – it can be overwhelming! In this post, we explore Passive House. What is it? What does it mean to build that way? And, why would you want to?
February 20, 2014
The chilly weather and a recent meeting at the über green Bullitt Center ("the greenest commercial building in the world") have me thinking about Passive House. Last fall, I attended a Passive House class through the Seattle AIA.
The Passive House Institute US (PHIUS) is a non-profit organization that verifies and approves super efficient buildings (not just houses) – meaning a building that achieves an overall energy savings of 60-70% over conventional building and provides 90% of its heating without mechanical means.
While the PHIUS standards deal mainly with energy use, other certifications, like the Living Building Challenge, deal with “the whole pie” of material use, site location, etc, and can be complimentary. The logic behind the concentration on energy use is the carbon footprint of a building: 8% in actual construction, 92% in energy use over its lifetime.
Reduced energy use is achieved by creating a super tight building that uses the sun for heating, through direct and passive solar gain, solar sinks and thermal masses, while providing appropriate shading for warm months.
Sam Hagerman of Hammer & Hand, President of the Passive House Alliance, presented examples of construction techniques frequently used in Passive House Buildings to ensure a “Stem to Stern” blanket of insulation, including liquid applied membranes and flashing, multi-layered walls that eliminate thermal bridging and argon filled triple pane windows with a U-factor of 0.125, with other features such as adjustable exterior shading and louvers and heat recovery ventilators. He estimates the cost to do a Passive House is 5-10% more than conventional construction.
Graham Irwin, a certified Passive House Consultant, presented some interesting numbers relating to air leakage. In standard construction homes, 40% of air leakage comes from the crawlspace, which is detrimental to indoor air quality because of potential radon infiltration. The average home in the US has the equivalent of a 3 square foot hole due to small air leakage. A 9mph wind effectively produces a 30% drop in R-value (the measure of thermal resistance in building materials, the higher the better).
Check out this handy list of Certified PHIUS Projects.
How do you build and certify a Passive House building? Explore the Step-by-Step Guide and Fee Structure.
