Attic Knee Wall Insulation

The traditional approach is to insulate the kneewall and the attic floor behind the kneewall.

Attic knee wall insulation.

This method can be made to work but the necessary air sealing details are demanding and fussy. The third point is the knee wall and crawlspace floor drywall. The main purpose of this material is to seal the fiberglass batts. Install a continuous air barrier on the exterior side of the attic knee wall framing with a rigid air barrier or other supporting material to prevent the knee wall cavity insulation from sagging and to create a continuous thermal barrier.

I call this tin foil on steroids because that s what it is. Knee walls that share space with a conditioned room in your home should have a combination of both traditional insulation and foil radiant barrier insulation. Any penetration between the conditioned interior air and the knee wall space needs to be sealed tight. First you will want to add traditional insulation between the studs this can be batt insulation spray foam or even rigid foam insulation.

How to insulate knee walls. Then you can add atticfoil on top of the traditional insulation by stapling it to the wall studs. This includes built ins recessed lights vent fans duct work and electrical outlets. Rigid air barrier material could include rigid foam insulation drywall plywood or osb among others.

Insulating only the attic roof rafters and the walls at the end of the attic is one method some use to insulate the knee wall area underneath but carson dunlop author of principles of home. The fourth point is between the roof rafters over the knee wall top plate.