Unvented CEiling Design

Neal Young
7/13/2014
I'm finally finishing my unvented cathedral ceiling and seeking guidance for the final stages. White metal panels, 26g, with above sheathing ventilation (3/4" battens under 1 1/2" counter battens). 30lb felt over 3/4" plywood decking. 2 parts to the ceiling: 1. 2x6 rafters - not vented under. I've installed 5 1/2" XPS in the rafter bays and sealed edges with great stuff foam. (I actually caulked all places where plywood met and where rafters meet plywood in each rafter bay prior to adding the XPS) This portion is complete since the xps is even with the rafter bottoms-ready for sheetrock. 2. 2x10 rafters - I've installed 5 1/2" XPS in the rafter bays and sealed edges with great stuff foam. (I actually caulked all places where plywood met and where rafters meet plywood in each rafter bay prior to adding the XPS - Thus I feel like I'm well air-sealed) There is no air vent at all in any of the ceiling. I have 3 1/2" space left below the xps in the 2x10 section and will install 1/2" drywall, tape then will install a pine tongue and groove ceiling under the sheetrock. I have enough rolls of R-13 faced fiberglass to fill the 3 1/2" space. My question here is - Should I put the face size toward the conditioned space or does it matter in my assembly?
Info @windowsonwashington.net
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7/13/2014
I would put the facing towards the foam in the this case. You don't need any moisture control in your area of the country and at minimum, the warm side is to the outside. The theory is that putting it to interior side would form a vapor trap but I don't see issue either way. Better yet, return the fiberglass and get either unfaced fiberglass or Roxul.

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