Combining Foam and Fiberglass Insulation Layers?
Asked Jan 21, 2009, 10:27 AM
I am insulating the upstairs of a cape cod and am trying to maximize the R-value without creating any moisture problems. The picture below illustrates my plan (the multiple layers of R-13 are due to framing issues which aren't shown).
My question concerns the 2" Owens Corning Foamular insulation on the sloped ceiling. My thinking is that the Foamular can be used to create the ventilation gap below the roof sheathing, as well as provide additional R-value. Although this theoretically creates a double vapor barrier, the ends of the fiberglass batts are open which should provide a path for moisture to leave this cavity. (I don't want to put the Foamular inside the framing because I don't want to loose any more space.)
Should I be concerned about moisture here, or should I be OK?
Thanks in advance for any help and thoughts!