Roof Insulation Calgary

Roof Line, Not Attic Floor

Most insulation work happens on an attic floor, with the attic left vented and outside the building envelope. Roof insulation is the other approach: the foam goes against the underside of the roof deck, which brings the whole volume beneath it inside the envelope. That is the right answer for a vaulted ceiling with no attic above it, for a converted or finished attic, and for any roof where mechanical equipment or ductwork sits in the space below.

Vaulted and Cathedral Ceilings

A vaulted ceiling has no attic to fill, so the insulation has to live in the rafter cavity itself, and that cavity is usually shallower than the R-value would like. Closed cell foam delivers more R per inch than anything else that fits there, and it air seals the assembly at the same time, which matters because a vaulted ceiling has no buffer space between the living area and the cold deck above it.

Low-Slope and Commercial Roofs

On a flat or low-slope commercial roof the assembly is different again, and the questions are about the existing membrane, the deck material and where the vapour control sits. Spray foam applied to the underside of the deck insulates and air seals in one pass without disturbing the roof surface above. What matters is understanding the whole assembly before adding to it, rather than treating it as a bigger version of an attic.

Ventilation Changes When a Roof Is Sealed

A vented roof assembly relies on airflow between the insulation and the deck to carry moisture away. Sealing the deck with foam removes that airflow by design, because the assembly is now unvented and the foam itself is managing vapour. That is a deliberate change to how the roof behaves, not a side effect, and it needs to be planned and explained rather than discovered later. Anyone sealing a roof line should be able to tell you what is handling moisture afterwards.