Martin – Knee wall and foam
Martin, I recently asked question about air washing insulation in knee wall applications and you suggested foam backing and said it would not create a double moisture barrier. (can’t seem to add a follow-up question to the thread) I have since read several other posts on this site which suggested that foil faced foam in this application would create a moisture trap. Please clarify.
I was planning to use 3 1/2 fiberglass, as the application is in a truss with 2×4 “wall” chords, and then poly over the studs. Therefore, is there a particular type of foam to use on the back side for safest install, EPS, XPS, Foil or no foil.
any other suggestions.
Best practice for attaching foam? glue, nails and plastic washers?