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T&G cathedral ceiling air barrier question

We are located in the Finger lakes region of NY and are considering T&G cathedral ceiling. Roof assembly would be Zip Roof Sheathing, un-vented roof with 7" of closed cell foam (R-49). I found a company that uses Lapolla Foam Lok 2000 4G foam with climate-friendly blowing agents. Based on this assembly, I am assuming that I would not need a dry wall layer under the T&G; am I correct?

Asked by Nina in CNY
Posted Mar 20, 2017 9:47 PM ET
Edited Mar 21, 2017 8:40 AM ET

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1.

Nina,
You won't need an interior air barrier, but you are still required by code to have an interior thermal barrier (to protect the spray foam insulation from fire).

Check with your local code inspector (your local building department) to determine whether your tongue-and-groove boards would be approved as a thermal barrier in your jurisdiction. You may be required to install 1/2-inch drywall as a thermal barrier.

-- Martin Holladay

Answered by Martin Holladay
Posted Mar 21, 2017 5:14 AM ET

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