Have you heard of a Passive House? In the world of sustainability, it’s one of the most intriguing design concepts to date.
Popular for its promise to significantly cut energy use for any type of building, and in any type of climate, the globally recognized design technique’s success comes from airtight building, super insulation, thermal mass, and passive solar design.
To see just how promising the technique is, Certifed Passive House Consultant Andrew Michler decided to try it out for himself in the Colorado Rockies.
“I was keen to put Passive House design to the test in the Colorado Rockies, where the winters can be brutal and living off-grid comes with a tiny energy budget,” he said. “The house I ended up building definitely lives up to its promises in terms of energy conservation, but the biggest surprise is how comfortable it is. Read on as I tell my story about how I came to build Colorado’s most energy-efficient house.”
The concept originated in the United States and Canada in the 1970s and 80s following the oil embargo and resulting energy crisis of 1973. Physicist William Shurcliff then created the technology’s five main principles in 1986:
a) thick insulation
b) airtight construction
c) prevention of moisture migration into cold regions within the walls, and other regions where condensation could occur
d) optimum sizing of window areas
e) a steady supply of fresh air
Dr. Wolfgang Feist, a German physicist, and Dr. Bo Adamson, a Swedish scientist, led the effort to take the founding principles of the concept and develop the design techniques to create the first “Passivhaus” in Darmstadt, Germany. Feist then founded the Passivhaus Institut (PHI), headquartered in Darmstadt.
PHIUS co-founder Katrin Klingenberg followed Feist’s lead and re-introduced the now-refined Passive House principles to the United States in 2002 by way of constructing her own residence in Urbana, Illinois.
Michler spent years building, researching, and writing about green design, eventually finding an intense fascination with the Passive House concept. He explained that while, “in Europe it is catching on quickly, and is even being incorporated into the code from New York City to Vancouver BC, it is still considered exotic to many designers and builders.” “From the thick walls, triple pane windows, and sophisticated fresh air system, to the extensive energy calculations, Passive House design leaves little to chance and the certification process can be arduous,” he continued.
Michler ultimately chose to to get his certification to build his own Passive House through the Passive House Institute (PHI) in Germany. The finished home is only powered by solar electricity and has a small propane hydronic heating system. The main heating source of the home is the sun, while the “waste” heat of the occupants and appliances comes in second. The final avenue is a small hydronic heating loop in the wall and at the Heat Recovery Ventilation system.
The home has been occupied for a year, and while it uses practically no energy for heating, the real take away is how comfortable it is. The house tends to naturally hover between 67 and 77 degrees Fahrenheit without heating or cooling. I use the heating system sparingly, so during a recent cold spell, when exterior temperatures reached -10 degrees, I let the house get down to 62 degrees. After taking a shower, I was surprised that it did not feel chilly like in most houses.
Michler found that the heavily insulated building envelope reduces heat loss through conduction, and as a result, there is no cold air coming in, or interior air circulating by cooling convection. The radiantly neutral surfaces are a game changer, most notably the triple pane glass. “My bare (and damp) skin does not bleed heat via radiation to cold surfaces, which in turn reduces the need for extra layers,” he said.
Unlike a passive solar building, which uses up to 50% of a home’s south side for glass, Michler’s house uses only 20% glass on the south side. This ensures the home doesn’t heat up to an uncomfortable degree, or lose significant heat. “That balance pays off in simplifying heating and cooling needs,” he explained.
Michler also noted potential changes in health and indoor air quality:
I tried to minimize potential risks by building with low-processed materials like plywood, timber, tile, and cellulose and mineral wool insulations. But activities like cooking can still be problematic, so the University of Colorado Boulder is measuring my home’s indoor air quality to see how a passive house compares to a typical house in terms of indoor air quality. I’ll keep you posted!
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