Kraft paper on batts with polyiso
I am building a separate accessory structure in Southern California. It has an unvented cathedral ceiling. It has an asphalt shingle roof sheathed with radiant barrier. The plans call for closed cell rigid R-12.5, then batt R-30, then 5/8′ drywall. My plan was to use 2″ polyiso tight against the radiant barrier (roof sheathing). The polyiso would have the foil toward the inside (against batt). Is it better to install the batts with or without kraft paper and which way should the paper face? Toward the drywall or toward the polyiso. Also, would it mater if there is gap between the drywall and the batt or the batt and the polyiso due to the rafters being deeper than the insulation buildup. Thank you.
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