Colorado's first certified International Passive House is nestled in the foothills of the Rocky Mountains north of Denver. The 1,200-square-foot MARTaK house, designed by architect and author Andrew Michler, is used primarily as an off-the-grid workspace. The structure has now been occupied continuously for six months. Has it met Michler's energy expectations?
"Yes," Michler says, "it's gone well past my expectations. ... We haven't turned on the heating system this year."
A solar array shared with a neighboring home provides all electrical power and most of the heating, with a propane-powered hydronic system serving as backup. Passive House Planning Package software was used to find the most efficient mix of insulation, windows and shading. Natural, nontoxic and recycled materials are used throughout the house.
Biobased phase change material with a melt point of 23º C is used to help even out temperature spikes. The PCM is contained in 500 square feet of ENRG Blankets made by Phase Change Energy Solutions. Most of the material is installed a south-facing interior wall.
Is it possible to measure the PCM's impact on overall performance?
"That's the question that I haven't found anybody able to answer," Michler says. "It's more about experiential. It's hard to isolate the PCM performance. There's no good modeling software for this. ...
"Overheating has been the biggest issue with passive houses, and we're seeing some anecdotal success with PCMs. We had a really warm fall, and the PCM did seem to level out the interior temperature, leveling out at 78 degrees Fahrenheit."
Has Michler used PCM in other projects? "No, this is the first. I do have interest in trying it again."