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

Roof foam – 2 or 4 layers?

John P. | Posted in Green Building Techniques on

I’m insulating the exterior of a gambrel barn. The roof needs 8″ of XPS insulation, and I’m wondering if two layers of 4″ foam will sufficiently block airflow to the roof deck, or if I would be better off doing four layers of 2″ foam. I’m doing this myself, so 2 layers will be easier to handle, I think

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. GBA Editor
    Martin Holladay | | #1

    John,
    I think that two layers will work well, especially if you tape the seams of each foam layer with a high-quality tape. Needless to say, it's important to stagger the seams of the second layer of foam with respect to the first layer of foam.

  2. John P. | | #2

    Ok - sounds good. I am going to stagger the seams - not too sure how I'll do that where the roof angle changes, I suspect I will just end up filling those transitions with spray foam.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |