Brad Steeg’s Seattle home was built in 1915, and from the description he provides in this post at GBA’s Q&A forum, it’s not hard to understand why Steeg is so uncomfortable during the winter: not much insulation, single-pane windows, and lots of air leaks.
“During the winter, my thermostat reads 70° but it still feel cold because the cold walls and ceiling suck the heat out of my body,” Steeg writes.
Exterior walls on the single-story, 900-square-foot house are framed with 2x4s. Steeg says some fiberglass batt insulation has been “stuffed in nooks and crannies” as previous owners opened up walls in the past. But the insulation is apparently spotty, and what’s there is dirty, indicating plenty of air gaps.
His plan is to add Tyvek housewrap, two layers of 2-inch-thick Roxul ComfortBoard 80 mineral wool insulation, 2×4 furring strips to create a rainscreen gap, and, finally, fiber-cement siding. Ceiling insulation will have to wait until an electrical upgrade in the future.
Steeg’s single goal is “comfort.” The question for this Q&A Spotlight is whether he’s on the right track.
Air-sealing before insulation
A continuous layer of insulation on the outside of the wall is typically a good idea, but adding insulation to a wall with lots of air leaks is putting the cart before the horse, suggests Dana Dorsett.
“Adding insulation over an air-leaky wall isn’t the best investment, since the air leaks can be anywhere,” Dorsett says. “Whether you add insulating sheathing or not, fixing the air leaks is the first order of business.”
One option would be to drill holes through the siding and sheathing (or removing a clapboard) and blowing in either cellulose or fiberglass from the outside of the house. That, Dorsett says, would “tighten things…