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

Flat roof insulation?

myoon595 | Posted in GBA Pro Help on

I am converting the sun room to a bedroom
My concern is about the ceiling insulation and ventilation.
the roof is flat and not insulated at all.
The previous owner blocked all air flow from soffit using pieces of wood which also supports the roof.

During the summer time, the asphalt flat will be stressful because of no air flow.
Therefore, I thought that need to air ventilation. However, during the winter time. if cold air come in though air vent, The inside would be very cold because of the thin insulation. I used 2*6 joist because of low ceiling so that only 6 inch space are available.

If I keep blocking the air flow, I worried about ice-damm because of not enough insulation.
Would you give me an advice?
Thank you in advance

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 insulate the roof. It's possible to create a vented roof assembly or an unvented roof assembly -- the choice is yours.

    However, the details are tricky. I suggest that you follow the recommendations in this article: Insulating Low-Slope Residential Roofs.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |