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

I’d rather put 2″ of rigid foam on the interior of the rafters than on top of the roof deck.

Seth Kelley| Posted inGeneral Questionson

I have 2×12 rafters and was planning on insulating with dense pack cellulose or rock wool for a cathedral ceiling. Then putting rigid foam on the inside , then drywall. Does this make sense? I was hoping not to vent. Will this work.

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.

Replies

  1. Seth Kelley||#1

    Forgot to mention I'm in central Vermont

  2. Aj Builder, Upstate NY Zone 6a||#2

    Venting that assembly is safer.

  3. GBA Editor
    Martin Holladay||#3

    Seth,
    Building codes require, and most building scientists recommend, that you include a ventilation channel between the top of the cellulose layer and the underside of the roof sheathing if you choose to install cellulose between your rafters.

    For more information, seeHow to Build an Insulated Cathedral Ceiling.

  4. William Goodwin||#4

    I think most builders would say rigid foam on the inside of a cathedral ceiling would be preferable, as long as the ceiling is vented, which with dense pack cellulose means plywood rather than foam baffles. Non vented would be considered risky.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |