How do you build a cathedral ceiling?

Raoul Lions Published: Oct. 19, 2019, 8:07 a.m.Last updated: Dec. 1, 2019, 6:19 p.m.

to vent or not to vent a cathedral ceiling.

I'm leaning towards not venting my cathedral ceiling and using closed-cell spray foam insulation. My walls are double 2x4 stud walls 12 inches deep and will have 2-3 inches of closed cell spray foam insulation to create a air and vapour barrier first, then the rest of the cavity will be filled with dense pack cellulose insulation, with an intello vapour barrier holding cellulose all in.

I'm wondering if I can do the same for vaulted ceiling? or am I better off going with straight closed-cell foam insulation.

The builder is using 16.5 deep trusses 24” off centre, I want to achieve R-80 in roof.

Responses (1)

Ecohome Oct. 23, 2019, 2:16 p.m. Reply

The coat of continuous insulation always works on the outside of dense packed cellulose by ensuring that the dew point is never attained within the cellulose. That said, continuous is just that, and roof rafters tend to create thermal bridges. Even with important levels of rigid insulation in the roof, it is best practice to double strap over the roof and vent anyways. Better to be safe than sorry.

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