Attic insulation: open cell or cut and cobble rigid foam?
Hi, I live in climate zone 4a and have a conditioned attic to insulate between rafters. Reading about moisture condensation issues, I looked into closed cell spray foam. Turns out that no spray foam company wants to install a type of foam that has low global warming potential such Icynene EcoSeal Pro. So that leaves me with open cell or rigid foam. I understand that both may let moisture laden air condense against the underside of the rafters, for slightly different reasons. Which method is less risky in that respect? Also would it help if I left a inch deep ventilation channel between the underside of the roof sheathing and the cut and cobble rigid foam? I have no ridge vents, I am not sure that any moist air has anywhere to escape to. In either case, (open cell or rigid foam) I was planning on following with existing R 19 fiberglass. Thank you !
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