Attic Knee Wall Insulation

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.

Attic knee wall insulation.

How to insulate knee walls. 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. Any penetration between the conditioned interior air and the knee wall space needs to be sealed tight. Knee walls have r 13 fiberglass rolls also called batts in them covered with stapled on reflective insulation.

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. The third point is the knee wall and crawlspace floor drywall. The traditional approach is to insulate the kneewall and the attic floor behind the kneewall. There are two ways to insulate triangular attics behind kneewalls.

First you will want to add traditional insulation between the studs this can be batt insulation spray foam or even rigid foam insulation. A better approach is to insulate the roof slope above the attic. Rigid air barrier material could include rigid foam insulation drywall plywood or osb among others. Then you can add atticfoil on top of the traditional insulation by stapling it to the wall studs.

The fourth point is between the roof rafters over the knee wall top plate. This includes built ins recessed lights vent fans duct work and electrical outlets.