Helpful? 0

I'd rather put 2" of rigid foam on the interior of the rafters than on top of the roof deck.

I have 2x12 rafters and was planning on insulating with dense pack cellulose or rock wool for a cathedral ceiling. Then putting rigid foam on the inside , then drywall. Does this make sense? I was hoping not to vent. Will this work.

Asked by Seth Kelley
Posted Sun, 04/06/2014 - 20:41


4 Answers

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Forgot to mention I'm in central Vermont

Answered by Seth Kelley
Posted Sun, 04/06/2014 - 21:35

Helpful? 0

Venting that assembly is safer.

Answered by aj builder, Upstate NY Zone 6a
Posted Sun, 04/06/2014 - 23:13

Helpful? 0

Building codes require, and most building scientists recommend, that you include a ventilation channel between the top of the cellulose layer and the underside of the roof sheathing if you choose to install cellulose between your rafters.

For more information, see How to Build an Insulated Cathedral Ceiling.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 04/07/2014 - 06:24

Helpful? 0

I think most builders would say rigid foam on the inside of a cathedral ceiling would be preferable, as long as the ceiling is vented, which with dense pack cellulose means plywood rather than foam baffles. Non vented would be considered risky.

Answered by william goodwin
Posted Wed, 04/09/2014 - 06:18

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