Foil faced ISO over 3″ closed-cell spray foam?
Looking for an answer before I start this project. I live in northern MN. I had my attic spray foamed 4″ behind knee walls, 3″ in the living space. This is a 1 1/2 story with a non-vented roof. I want to know if its O.K. to use foil faced 1″ rigid sheets to cover studs [Editor’s note: I think David means “rafters”], with the foil facing down between the knee walls. I did plan on filling all voids and foil taping the joints. Then 1/2″ sheetrock over the foam. Just want to make sure this isn’t considered a double vapor barrier, and if this would be considered good construction.
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