“TrekHaus," a Passive House duplex in Portland, Oregon, certified by PHIUS is designed to use just 12.5 kWh/m2/yr for heating.
By Paula Melton
The Passive House standard, often admired for simplicity, has also been criticized for rigidity. Now that Passive House Institute U.S. (PHIUS) has achieved independence from Europe and started its own certification system, called PHIUS+ (see ”Passive House U.S. Develops Separate North American Certification,”EBN Dec. 2011), the group is proposing changes that would relax the Passive House standard for some projects. PHIUS cofounder and executive director Katrin Klingenberg cites cost-effectiveness as the rationale behind her proposals.
The PHIUS technical committee has yet to work out the details—Klingenberg doesn’t expect a complete draft of the specifics to be available until the spring of 2012—but Klingenberg explained the gist of the proposed changes: while it’s theoretically possible to achieve the Passive House standard in any climate, doing so in a very cold climate can end up being so expensive that the cost cannot be justified over the lifetime of the building. Klingenberg recently laid out her ideas in a blog post titled “15 kWh Is Dead. Long Live 15 kWh”—a reference to the central requirement that Passive House buildings use no more than 15 kWh/m2/year for heating and no more than 15 kWh/m2/year for cooling. That metric has been one of just three performance requirements; the other two involve airtightness and total source energy, and the proposal calls for rethinking these other metrics as well.
“Cost is a very important core concept of Passive House,” she told
EBN. While not an express part of the performance metrics, she argues, cost was always part of the reasoning behind investing in the envelope instead of the mechanical system. “We’re going to do the exact same thing—come up with a cost-effective solution of minimal space conditioning in very cold climates,” she said. “It’s nothing different from what they did in Europe.” Klingenberg thinks the relaxation of the standard should be made on a case-by-case basis, although it’s possible that modifications may be made by climate.
Public responses to Klingenberg’s post have been mixed, with many applauding the spirit of the proposal and others arguing that a revised standard should not bear the name Passive House. Erik Lobeck, an associate at Rob Hawkins Architect, commented on the post to praise the efforts, offering a litany of built-in “penalties” he must overcome as a Passive House consultant: small size, urban infill, and extreme climate, he said, all make it harder to achieve certification.
Mike Eliason, a certified Passive House consultant at Brute Force Collaborative in the Seattle area, questioned the move in an interview with
EBN. He appreciates the “purity and beauty” of the international Passive House standard just as it is. “This is not really going in the direction that we need to be going,” he asserted. “I feel like we should be aiming for a set level of consumption that’s even
more conservative than most Passive House houses that are certified.” Eliason pointed out that single-family homes are the only buildings that typically have trouble achieving Passive House certification cost-effectively in extreme climates. “In the bigger picture, maybe we should be huddling together for warmth” in multifamily dwellings, he suggested, rather than building conventional suburban homes in Alaska.
Eliason also argued that many of the Passive House projects completed so far in the U.S. hadn’t started out that way, and trying to “shoehorn” existing projects into the Passive House standard would naturally make these buildings more expensive. He added that achieving Passive House certification is likely to get less expensive as time goes on. “There’s a cost optimization that happens
after you’ve done a project or two,” he told
EBN. “It’s similar to LEED; the first couple years were horribly expensive. Now there are firms that pump out [LEED projects] at no additional cost. I think we’ll get there, but I think it will take a little bit of time.”
It is still possible to pursue certification under the international Passive House standard in North America. Many building certifiers, unlike PHIUS, are still recognized by the international Passive House Institute, which has no stated plans to relax the standard based on climate or cost.