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moisture trap Post New Topic | Post Reply
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Posted: Jun 22, 2010 08:44 AM
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moisture trap
I,m building a new house in Fl and am thinking of spraying the attic ceiling with closed cell f oam, i also would like to install GAF Weather Watch, {which is a stick down sealer} on my roof deck under the shingles.would there be a problem with traping moisture between them?
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mason
Posted: Jun 22, 2010 10:32 AM
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You are adding a vapor retarder element to the roof deck, but assuming your interior humidity is not excessive, it should not be of major concern. Just be sure the foam (if closed cell) is sufficient thickness to separate the interior an exterior temperature to reduce the potential for achieving a dewpoint within the foam or interior portion of the assembly. (Check with the latest IBC and IRC code books for specific thickness of foam in your area). And if it is an open cell foam in a cold climate or marine zone 4 that a vapor retarder element is added to the warm-in-winter side of the insulation or other factors used to reduce the potential for moisture condensation. Also be sure the shingle warranty is not compromised by an unvented attic configuration. Does anyone know if GAF approves unvented attics in their warranties? |
