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

Vaulted ceiling insulation

robpage | Posted in Energy Efficiency and Durability on

I’m fixing up my garage, looking for some insulation guidance. The framing was done by somebody’s grandfather in the 40’s and it’s real crazy, but then, it’s stood there in southern CA earthquakes for about 70 years so I’m not too worried about it. Anyway, I’d like to attach T & G or drywall directly to the roof rafters, to keep the vaulted look but can’t figure out how best to insulate it since there’d be no attic.

idea #1: put Dow Tuff-R rigid insulation in between the rafters, fill in gaps with Great Stuff foam.
idea #2: if I go with T & G, drop in Green Fiber Insulation as I work my way up.
idea #3: somebody told me there’s a Thermax board that’s white and attractive looking that could be attached directly to the rafters and would look as nice as painted drywall and provide adequate insulation.
idea #4: spray foam
idea #5: ??

The spacing for the rafters is all over the place so batt insulation probably isn’t an option? (Plus I keep hearing fiberglass sucks?)

See attached image.

Thanks in advance for any advice!

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

    You need to made a basic decision first: do you want an unvented roof assembly or a vented roof assembly?

    I suggest you start by reading this article: How to Build an Insulated Cathedral Ceiling. After reading the article, if you still have any follow-up questions, you can post your questions here.

  2. robpage | | #2

    Thanks Martin, that article was very helpful!

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |