Do I need a vapor barrier in an unvented roof assembly?
I am building a roof assembly with 2×10 rough hemlock rafters exposed on the inside with cathedral type ceilings and no interior insulation. Rafters are covered with 3/4″ pine shiplap decking, then 5 1/2″ of polyiso insulation (2 layers of 2 3/4″, joints sealed and overlapped), then 1×3 strapping, then metal roofing panels. I’m wondering if I need to include a vapor barrier anywhere in this assembly, and if I should put tar paper on top of the polyiso and underneath the strapping? The polyiso is paper faced. I am in upstate ny.. thanks for any advice!
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