Nowhere punishes a leaky attic like Calgary. A chinook can swing the temperature 20 degrees in an afternoon, and that freeze-thaw cycle is exactly what turns escaping attic heat into ice dams at the eaves - melt by day, refreeze at the cold edge by night, water backing up under the shingles. In a city where more than half the homes predate 1991-era sealing standards, the attic is usually the first place the building loses the fight with winter.
Why chinooks make attic air-sealing non-negotiable
A steady cold climate is almost easier on a roof than Calgary's whipsaw. Each thaw-freeze swing drives moisture and pressure changes through every unsealed pot light, bathroom fan and top plate. Spray foam matters here because it air-seals as it insulates - it doesn't just slow heat, it stops the leak that feeds the ice dam.
Two ways to do a Calgary attic
- Vented attic (most Calgary homes): air-seal the ceiling plane with foam at the penetrations, then top up with blown-in to reach R-38 affordably.
- Unvented / cathedral / bonus-room-over-garage: spray the roof deck with 5-8" of closed-cell to bring the space inside the envelope - common in the newer NW communities like Tuscany, Royal Oak and Sage Hill with complex rooflines.
What Calgary homeowners notice after
- The upstairs rooms finally hold heat through a cold snap.
- The furnace stops short-cycling against the drafts.
- The recurring eaves ice dam - and the meltwater stain it caused - stops coming back.
Reaching R-38 takes about 6" of closed-cell or 11" of open-cell; estimate yours, then get a free Calgary quote. More on attic foam province-wide.