Can 1.5″ and 2.0″ unfaced XPS be used as a continuous rafter baffle?
I am considering using either 2.0 or 1.5 XPS as a continuous rafter baffle (from soffit to ridge vent) using a 2″ vent between the XPS and the the roof deck. The rafters are nominal 2x10s and the underside of the rafter will be insulated with Roxul and then covered with finished plywood with a high quality latex paint (Class II or preferably Class III vapour retarder). I have only seen 1″ XPS recommended by GBA. Can a thicker board be used or is there concern re: drying to the exterior given the relative impermeance of the thicker board?
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