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Our April EBN feature article--"Passive House Arrives in North America: Could it Revolutionize the Way We Build?"--went online today. This was a fun article to research and write, because it put me in touch with my low-energy building roots. Until digging into the history of Wolfgang Feist's German Passivhaus standard, I hadn't realized that this building system really had its origins in North America--with the passive solar energy and superinsulation movements of the late 1970s (back when I got involved in this field while working in New Mexico).
Feist combined passive solar and extraordinarily well-insulated building envelopes to create buildings (both residential and commercial) so energy efficient that they can be heated using ventilation systems with small, 1,000-watt, in-duct electric heaters. Feist credits Amory Lovins of the Rocky Mountain Institute with this idea--that by investing in the building envelope, heating and cooling systems can be downsized dramatically. Energy loads are so small that buildings can be made net-zero-energy by installing rooftop PV.
Germans are known to value precision, so it is little surprise that the Passivhaus standard is highly quantitative, rigid, and performance-based. In bringing Passivhaus across the Atlantic and creating the Passive House Institute – U.S. (PHIUS), German-trained architect Katrin Klingenberg adopted the German standard exactly, retaining the 15 kWh/m2/year (4,755 Btu/ft2/yr) standard for heating, the same standard for cooling, a total primary energy consumption (including lighting, appliances, and plug loads) of 120 kWh/m2/yr (38,000 Btu/ft2/yr), and an airtightness standard of 0.6 air changes per hour at 50 pascals of pressure difference across the envelope (0.6 ACH50).
What I like about Passive House is how clear it is. The energy consumption and airtightness targets are spelled out precisely, leaving very little room for ambiguity. And those standards are really rigorous. If a house meets the Passive House standard it will be one of the most energy-efficient buildings in the country--period. As noted above, taking such buildings to the next step--making them net-zero-energy--is relatively easy.
The problem with Passive House is that same rigidity. The Passive House requirements could be tweaked, I believe, to make it work better in North America and for existing buildings. Background on these ideas is covered in the EBN article, but let me get right to a handful of specific recommendations. I'll look forward to comments about why these suggestions do (or don't) make sense, what I'm missing, what else could improve Passive House, and any other comments you might have.
What do you think? Are these three recommendations reasonable? If not, what would you suggest? Post comments below.
Alex Wilson is the founder and executive editor of Environmental Building News. To keep up with his latest articles and musings, you can follow him on Twitter.
Photo: Dan Whitmore of Blackbird Builders used a "Larsen truss" detail in this Passive House he is building in Seattle for his family. The 14" wall cavity will be insulated with dense-pack fiberglass to achieve approximately R-55. Photo: Dan Whitmore.
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In our case I think the air barrier (Huber's Zip sheathing) is vapor-impermeable to a significant extent. It is a coated sheathing..." More...
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