Rigid Foam Attic Knee Wall

I d prefer to see a rigid material on attic kneewalls.

Rigid foam attic knee wall.

The higher the knee wall the greater the amount of useful wall space you create in your finished attic. Added bonus the floor of this knee wall leaked too so there is a line of foam just above the floor joist. Wondering how you can make your knee wall space insulated correctly. An insulated kneewall is effectively an exterior wall so you ll need a layer of rigid foam drywall osb or thermoply on the back side of the kneewall to prevent cold air from degrading the performance of the insulation.

How to insulate knee walls. I think the rigid material will do a better job with air sealing and will stay intact longer. Seal all the edges penetrations and seams. It easily expands with graphite infused right into the foam while we air seal the edges to provide the full maximum insulation.

Both can be done poorly of course and i ve seen both done poorly. 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. This method of insulation won t work if the triangular attic includes ducts or plumbing pipes. Here are the three keys to sheathing an attic kneewall properly.

First you will want to add traditional insulation between the studs this can be batt insulation spray foam or even rigid foam insulation. Rigid air barrier material could include rigid foam insulation drywall plywood or osb among others. In this case after insulating the stud cavities with fiberglass batts use 1 inch minimum rigid foam insulation to cover the back of the knee wall which will prevent attic air from circulating around and through the insulation. Rigid foam insulation is innovative eye pleasing and super effective.

But you do so at the expense of floor space. We reduced the air leakage nearly 50 on this house in shaker heights without insulating the walls. Blown insulation in the knee wall and top attics. 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.

A knee wall is a short vertical wall roughly two or three feet high that blocks in that useless triangular space. We prefer cellulose but we use fiberglass sometimes too. Rigid foam insulation is the solution.