GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Can you place polyisocyanurate insulation for interior of cathedral ceiling?

SquakMtn | Posted in Energy Efficiency and Durability on

I have a 1966 house remodel with a cathedral ceiling that has 2 X 6 framing. I have removed the asbestos popcorn texture and sealed it with paint. The ceiling space is insulated with rock wool that was placed by the original builder. Not wishing to remove and disturb the existing drywall, my plan is to place 1 1/2 inch polyiso under the drywall existing and using 2X2 furring strips to support new drywall below that. My question and concern is condensation and whether to use the foil covered product – Rmax? The climate is that of the Seattle area. The space above the existing drywall is vented from the insulated area to the soffit with a continous eave vent on the soffit.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. GBA Editor
    Martin Holladay | | #1

    Foil-faced polyiso is fine in this location.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |