Air-Tight and Fresh

In 2016, the couple (who have young children) moved into their new Passive House. They chose the lot for its south exposure, which can be challenging to find among Calgary's residential lots. They wrapped the basement slab and walls in 8 inches of expanded polystyrene (EPS) foam.

They also installed a poly-vapor barrier below the slab and a water-proof membrane on the concrete. Fully wrapped to eliminate any thermal bridges, Crawford adds, the slab has an R-value of 35. The basement is also fully finished, as they rent it as a second suite or accessory dwelling unit.

Above grade, for the main level and the loft, the homeowners decided on a 2x6 wall with six inches of rock or mineral wool insulation and HardiPlank siding, bringing the walls to R-42. These choices, which resemble conventional wall construction, helped the couple secure their permits, pass city inspections, and find the right framer for the house. The roof has 16 inches of fiberglass for an R-60 value.

For most of the year, despite the Canadian climate, Valgardson has said, "we can get away with a 1500-watt heater—that's basically a hairdryer." On frigid days, the couple uses electric-resistance heat—"which we might change to a heat pump in the future," Crawford says—to bring the house to a comfortable temperature. A natural-gas instant hot-water tank provides hot water. The couple decided on Klearwall Passive House Certified windows. In the loft, those windows bring in light and heat.

While the house is air-tight, two Zehnder ComfoAir ERVs provide ventilation to the suite and upper levels. "We don't have a furnace," Crawford says. "The ERV exchanges moisture and heat; it's the lungs of the house. The ERV continuously filters and balances the fresh air. It exhausts air from the kitchen and bathroom, and recovers moisture from the air to preheat incoming cold air."

A 26-panel, grid-connected solar array delivers 7.2 kW, "which covers 40 percent of our total energy demand," Crawford says. "When we built the house six years ago, net-zero really wasn't a thing."

Six Years Later - Lessons Learned

The home's solar gain through the windows is better than expected, Crawford says. A lot better. "Officially, you're allowed to design for 10 percent overheating, which works well in Germany," he says of Passive House protocol. "We designed for 8 percent overheating, and that's too much."

"The more windows you have on the south, as well as glazing with high solar gain, results in 50 percent of the heat coming from the sun," he explains, "but in the shoulder seasons, when the overhangs let sunlight into the house, there are days so sunny the house overheats. Also, in the summer, my overhangs weren't as long as they should have been."