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Is ventilation needed for a closed eave overhang on a flat roof, no attic

poindextrous | Posted in General Questions on

I have yet to find any advice about my particular building detail. The roof has both a 1′ and 2′ overhang, closed off with 1x soffit boards. The main roof is low slope and sealed with spray foam, so there is no need for intake ventilation for ventilating the main body of the house roof. Rafter depth is a net 5″, 24″ o.c., covered with a Cool Roof rated TPO over plywood. Climate Zone 3, marine environment- night and morning clouds with sun in the afternoon most of the year.

The main reason for ventilation I read is to prevent condensation on the underside of the sheathing, but this area is not over a living space generating moisture. The other reason is to provide air intake for a ridge vent or similar, but that’s not applicable here.

If ventilation is required, I figure I can always drill holes and pop in those little round aluminum louvered vents, but I’d rather not have the expense, and see a row of prominent dots on the underside.

What do I risk by not adding vents? How big should the vents be if needed, and is one per cavity sufficient?

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  1. Expert Member
    Michael Maines | | #1

    It doesn't sound like venting would provide you with any benefit.

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