Is it wise to create an airspace between the roof and closed-cell spray foam to allow for venting?

Question

Is it wise to create an airspace between the roof and closed-cell spray foam to allow for venting?

Asked by C. Monte

My new home addition has both ridge and eave vents. We were thinking of putting 1- to 2-inch blocking/cleats and a 2" rigid foamboard, then applying 5 or 6 inches of closed-cell spray foam onto that so that there is breathability. The exterior roofing is metal. We were also going to spray-foam the walls built of 2 x 6s. The contractor recommends 3" in the walls. This would create an airspace between the faom and the plasterboard. What do you think?

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Answers

Lee Hall's picture

Although this sounds good, and housewrap companies sell systems to allow this, most foam producers do not recommend this type of installation.

I would contact the producer of the foam (not your contractor) -- tell them exactly your situation and follow their recommendations.

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