It’s a 2′ vertical 2×4 wall around a cathedral ceiling area in the living space that I’d like to increase the R value. Currently insulated with r-13 batt kraft paper fiberglass. Can I just add a 1 or 2″ foam board? Put another way, I’m wondering if I can insulate it similar to an exterior vertical wall, the difference being it’s not exposed to the elements, but definitely to higher temps in the summer. The house is located in NW North Carolina mountains, so moderately humid, moderate outdoor temperature ranges (normally 20-80 fahrenheit).
TIA