Roof Underlayment Product Recommendation
I am building a home with a conditioned attic. I will be spraying 11-12 inches of open cell foam underneath the roof sheathing. I need to allow the sheathing to breathe to the exterior, for it will not breathe to the interior with the 12 inches of foam. Thus, I was wondering if anyone was aware of a roof underlayment (other than building paper) that is breathable, durable, and that has a high exposure rate. I know that there are synthetics out there, but none has an appropriate perm rating (most are around 0.3 perms which would not breathe.) Ideally I would prefer a synthetic underlayment that has a perm rating of around 5.
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