Membrane in unvented roof
I am installing 1×6 T&G boards above my 2×8 rafers in an addition cathedral ceiling project. I plan to follow with a layer of 5/8″ plywood (for roof structure), and 6 inches of polyiso above that.
I am wondering if it’s OK to install the air sealing membrane above the tongue and groove, which would allow me to wrap it down out to the walls (T&G stops a the walls, but the plywood layer continues to the rake and eaves). I am concerned about that plywood layer trapped between the membrane and the insulation. Is this a risky configuration? Should I put the membrane above the plywood instead and air sealing at the exterior walls with foam insulation?
I am in Austin, Tx. I appreciate any feedback.
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