GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X 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

Is insulating the roof structure worth it

johnnydc | Posted in Green Building Techniques on

Hi all,
I feel like I’ve read a lot and, like many things in life, I end up still being unsure what the right thing to do is.  I’ve got to reroof my bungalow, and that is going to happen soon but not immediately.  It’s a 1.5 story side gable home. I’ve attached a picture, I think, from the front. It has one dormer on the front, none on the back.
The upper rooms get very hot in the summer. There are effectively two rooms there, and one of them was remodeled before we bought the house and has cathedral ceilings.  There is no vent on either side, and the cathedral ceiling side cannot be vented even if I wanted to because of that.

I keep thinking that putting down two layers of rigid foam on the roof before whatever roofing material we use would be helpful for keeping the upper story cooler. But then I read, here I think and elsewhere, that if you’re not going to do a super sealed roof structure, don’t bother and just let it be open. Of course being open is not really a choice because of the way the gables and the Cathedral ceiling are conspiring!

Any clear advice on this? I’m sure that this has been answered 100s of times on this site, so please forgive and feel free to redirect me if this has been answered clearly in another Q&A.
Thanks!

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. b_coplin | | #1

    If adding foam to the roof deck is ever going to be cost effective, re-roofing is the time. Certainly it is the most durable approach. Your other option is closed cell spray foam installed on the interior side of the roof deck. The thickness of foam, either above or below the roof deck, is climate dependent.

    Martin explains your options in great detail in this: https://www.greenbuildingadvisor.com/article/how-to-build-an-insulated-cathedral-ceiling

    The window sill in the dormer looks like it may be low enough that foam and a second layer of sheathing may present an issue. (Does snow ever pile up to the window as it is now?) This might push you towards an interior solution.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |