U.S. Group Will Relax Passive House Standard

By Paula MeltonThe 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.