GBA Logo horizontal- Facebook- LinkedIn- Email- Pinterest- Twitter- Instagram- YouTube Icon- Navigation Search Icon- Main Search Icon- Video Play Icon- Audio Play Icon- Headphones Icon- Plus Icon- Minus Icon- Check Icon- Print Icon- Picture icon- Single Arrow Icon- Double Arrow Icon- Hamburger Icon- TV Icon- Close Icon- Sorted- Hamburger/Search Icon-

Community and Q&A

How to air seal a sloped bonus room ceiling

Stephen Cook | Posted in General Questions on

I’m starting the process of building a new house in climate zone 4a.

It will have a “bonus” room above the great room. One area of the bonus room ceiling will be sloped as it will follow the roof line in that area. This will be one wall only and the sloped area will be approx 2′ in height, approx 18′ long. The rest of the ceiling above will have blown cellulose. It will be a vented attic space. Knee walls will also be cellulose insulation backed with an outward facing foil faced rigid insulation board.

The house will be 2×4, cellulose insulation, tapped osb, tyvek commercial D, covered with 1″ rigid insulation.

My question is how best to deal with that sloped area for both insulation and air sealing?

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. User avatar GBA Editor
    Martin Holladay | | #1

    The usual air barrier for a ceiling -- whether horizontal or sloped -- is the drywall.

    When it comes to insulating a sloped ceiling, there are many options. To learn about all of your options, see “How to Build an Insulated Cathedral Ceiling.”

    For information on kneewalls, see

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |

pajero sport