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

OSB radiant barrier on flat roof

David350 | Posted in Energy Efficiency and Durability on

I live in Los Angeles county and have a 1968 house with cathedral ceilings and asphalt shingles on the front part of the house. The back of the house is flat with torch down. All the roof has solid 1″x6″ covering. There is pretty much no attic but there is 6 inch rafters with pink fiberglass insulation in there. My question is: With this type of roof would it be worth it to add spacers and a layer of OSB radiant barrier when I re-roof the house? From what I see online it talks mostly about attics where there is more airspace so it is hard to tell how much of a difference it would make in a situation like mine. Any info that might help me decide will be appreciated.

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. Jon_R | | #1

    Here is some code to review. Local code could be different.

    1. David350 | | #5


  2. BirchwoodBill | | #2

    I think the rule of thumb is for 1.5 to 2.0 inches of an air gap for a radiant barrier. It varies based on the pitch of the roof and intensity.

  3. Expert Member


    I've only got the photos you posted to judge by, but have you thought of re-framing the roof so that it sloped from the ridge of the gable to the eaves of the (now) flat part? That might allow you to add insulation and use shingles.

  4. David350 | | #4

    Never thought of reframing...hmm that is something to think about. Thanks.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |