Rigid Foam Attic Knee Wall

First you will want to add traditional insulation between the studs this can be batt insulation spray foam or even rigid foam insulation.

Rigid foam attic knee wall.

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. Seal all the edges penetrations and seams. Both can be done poorly of course and i ve seen both done poorly. The disadvantage is that it would be very very hard to reach the desired r value from r 49 to r 60 depending on climate for attic insulation.

A knee wall is a short vertical wall roughly two or three feet high that blocks in that useless triangular space. Wondering how you can make your knee wall space insulated correctly. We reduced the air leakage nearly 50 on this house in shaker heights without insulating the walls. I think the rigid material will do a better job with air sealing and will stay intact longer.

Rigid air barrier material could include rigid foam insulation drywall plywood or osb among others. The higher the knee wall the greater the amount of useful wall space you create in your finished attic. This method of insulation won t work if the triangular attic includes ducts or plumbing pipes. Rigid foam insulation is the solution.

It easily expands with graphite infused right into the foam while we air seal the edges to provide the full maximum insulation. We prefer cellulose but we use fiberglass sometimes too. Blown insulation in the knee wall and top attics. Cover the whole wall.

Added bonus the floor of this knee wall leaked too so there is a line of foam just above the floor joist. 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. Here are the three keys to sheathing an attic kneewall properly. The advantage here is that your knee wall is probably already insulated this way so it s just a matter of buying some foam so cheap.

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