For years, the English-language website of the Passivhaus Institut in Germany provided this definition: “A passive house is a building in which a comfortable interior climate can be maintained without active heating and cooling systems. The house heats and cools itself, hence ‘passive.’”
The idea of a house that “heats and cools itself” has a certain PR value, of course. The only problem is that it doesn’t exist. Excluding a few buildings in areas with a very mild climate (for example, in San Diego or Honolulu), no one has yet managed to build a house that heats and cools itself. That’s why Passivhaus buildings always need an active heating system, an active cooling system, or both.
The chickens come home to roost
Until recently, most of the people complaining about exaggerations from the Passivhaus Institut were cynics and curmudgeons like me. Now, however, even Passivhaus fans have begun grumbling about the fallout from the false claim that Passivhaus buildings don’t need heating or cooling systems.
The myth is responsible for a great many misunderstandings — misunderstandings that can in some cases lead to bad building designs.
“Beware the Passivhaus Kool Aid”
Allen Gilliland is the founder of One Sky Homes, a design/build firm in San Jose, California. His company specializes in Passivhaus construction, and Gilliland designs all of his projects’ HVAC systems. In a recent PowerPoint presentation that he shared with a monthly meeting of a group called Passive House California, Gilliland expressed his frustration with the idea that a Passivhaus building “heats and cools itself.” In one of his slides, Gilliland warned, “Beware the Passivhaus Kool Aid: Hyperbole, careless references, and hearsay are everywhere.”
It is often said that a building with a low rate of air leakage and above-average amounts of insulation is inherently more…