Is this design OK for my vaulted ceiling?
I am new to this. I feel like I am back in college researching like crazy and finding too much info. This is the best site I have found. Keep up the good work. I have built several houses, but this one has a vaulted ceiling covering a 34 X 34 space. (This is my daughter-in-love’s request. How could I say “no”!) However, I am beginning to have second thoughts. This is what I have come up with due to a variety of reasons. Beginning from the outside: Metal roofing screwed down (sheets), radiant bubble wrap, one inch iso board felt covered, 7/16 osb, 2 x 12 rafters 16 in oc, either 7-8 inches of open cell foam or 10-11 inches of mineral wool, and finally car siding painted or stained. Leaving out the poly vapor barrier on the inside would allow drying to the inside.
We are in south central Indiana, last county in zone 4 next to zone 5. (70 miles sw of Indy) I have considered not doing the iso exterior, and go with 2 inches closed cell inside. However, the locals who do spray foam will spray closed cell directly to the roof sheathing only if I sign off, saying they are not responsible. They claim all I need is to use metal, bubble wrap, sheathing, 7 inches of open cell, car siding or drywall. They claim that with 7-8 inches of open cell, the water vapor never makes it to the sheathing. Help!!! 🙂
Obviously, there are some financial restrictions. But getting this vaulted ceiling thing right is probably more important than money in the long run. I do not want to do the vented thing.
Also, this same design would be used for the wall, using 2 x 6 walls and 4 inches open cell.
Again, “Thanks.” Mychief.
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