Insulating a cathedral ceiling
I am building a timber frame barn in zone 6 (Vermont), part of which is insulated. We hope to use recycled or seconds of polyisocyanurate in 4x8 sheets. The roof from the inside has 6x6 rafters, 7/8" T&G pine boards, moisture barrier, 2 layers of 3" polyiso, taped and foamed in cracks, 2x4 strapping screwed through the insulation into the rafters, another moisture or rain barrier, plywood underlayment nailed to the 2x4s, creating a 1.5" vent space, finally metal standing-seam roof. My questions are:
1. Is this a good way to go?
2. Do I need a vent space created by the 2x4s. Recently I read that vent spaces are not needed, but I also read that T&G ceilings are very permiable.
3. Is the compressive strength of the polyiso enough to withstand the installation (people walking on it) and the compression of the screwed down strapping.
4. We could also add a final layer of 1" or 2" "blue board" for additional srength. Is that necessary?
Posted Thu, 03/13/2014 - 13:51
Edited Thu, 03/13/2014 - 13:53
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