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

Insulating a cathedral ceiling

Mudball | Posted in Energy Efficiency and Durability on

I live in an early Lindell cedar kit home. I shan’t go into the construction method but it is far from conventional. I need to add insulation and also re- roof. I was thinking of stripping the roofing and sheathing, laying down either 2×4 or 2×6 rafters, filling the bays with Thermax insulation, sheathing and re-roofing. My question is if the rafter bay is not completely filled do I absolutely have to vent the bays. I understand that the reflective coating of the Thermax is only effective when used with an air gap, but to vent the roof, because of the original construction method, would be a total pain in the behind. Any and all ideas will be greatly appreciated.
Thanks ….Dave.

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. GBA Editor
    Martin Holladay | | #1

    Dave,
    It makes sense to add rigid foam on top of your existing roof sheathing if you are re-roofing. You don't need ventilation channels, as long as you install enough foam. And you don't need 2x4 or 2x6 rafters -- all you need is a thick layer (or two layers) of rigid foam, followed by a layer of plywood on top of the foam.

    As an alternative, you can use a product called nailbase. (Google it.)

    More information here: How to Build an Insulated Cathedral Ceiling.

  2. mrgregpittman | | #2

    I agree to what dave said you can use rigid foam for re-roofing and also the article given is very useful for us to understand how to build insulated cathedral ceiling.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |