Insulating in a Cold Climate
In a city that sees more chilly days than scorchers, proper insulation is key
At an elevation of 6,910 feet, it's no surprise that Flagstaff offers a cold, mountainous climate. The city's annual high temperature hovers around 60°F, while its low temperature average falls around 27°F. (To give some perspective, Denver sees annual average high and low temps of 65°F and 36°F, respectively, while Seattle sees average highs and lows of 60°F and 45°F, respectively.)
To help battle the cold temperatures, foam insulation was chosen for most of the insulation in the Model ReModel West home, beginning with Huber Engineered Woods' ZIP System R-Sheathing, rated at R-9, which puts a “blanket” of closed cell foam over all walls. Wall framing in the old and new parts of the home consist of 2x4s, so here, Owens Construction's Bill Owens had 3 inches of closed cell foam sprayed, deliberately leaving about a ½-inch of air space. (This sandwich of exterior and interior foam is good for a rating of R-30.)
The inside was then covered with Fi-Foil Company's HY-Fi, a hybrid insulation system with a reflective barrier that is designed to reduce heat flow by radiation and convection (this adds to the overall R-value). The ceiling received 3 inches of closed cell insulation (R-21) plus about 9 inches of open cell foam (R-35), providing a much higher R-value (R-56) than the R-49 required. HY-Fi will also cover the bottom of the rafters prior to drywall installation.
More important than the raw number, the closed cell foam acts as an absolute air barrier, unlike fiberglass. As a result, air infiltration numbers should be very low when Owens partners up with sustainable building consulting company Two Trails to run a blower door test.