Flash and batt for attic floor
I live in zone 7, old construction. Currently the attic i floor is insulated with fiberglass batts, obviously creating lots of problems with heat loss and ice forming on the roof under certain conditions. The roof itself isn’t insulated, so it’s a ventilated attic.
I’ve been offered to replace the batts with 4″ of closed cell spray-polyurethane foam. I am considering an alternative with a 2″ layer of closed cell foam followed by 5″ of fiberglass batts. This would save some money for me, especially given that I already have the batts. My understanding is that since I live in the cold climate, water vapors would be moving from the house to the outside for most of the time, and the closed cell foam would prevent them from escaping. Therefore the dew point issue is not relevant.
Any comments/ideas from the pros?
Thank you.
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Replies
Oleg,
The method you describe works well. Two inches of closed-cell spray foam does a good job of air sealing a ceiling.
My only recommendation is that you scrimp, save, or borrow the money to add more insulation on top of the cured spray foam. If you could afford to install 12 to 16 inches of cellulose on top of the foam, you'd have a well insulated ceiling.