Rigid Foam Attic Knee Wall

The higher the knee wall the greater the amount of useful wall space you create in your finished attic.

Rigid foam attic knee wall.

Blown insulation in the knee wall and top attics. First you will want to add traditional insulation between the studs this can be batt insulation spray foam or even rigid foam insulation. I think the rigid material will do a better job with air sealing and will stay intact longer. 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.

Both can be done poorly of course and i ve seen both done poorly. We reduced the air leakage nearly 50 on this house in shaker heights without insulating the walls. Added bonus the floor of this knee wall leaked too so there is a line of foam just above the floor joist. Rigid foam insulation is the solution.

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. Rigid foam insulation is innovative eye pleasing and super effective. Wondering how you can make your knee wall space insulated correctly. 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.

We prefer cellulose but we use fiberglass sometimes too. A knee wall is a short vertical wall roughly two or three feet high that blocks in that useless triangular space. It easily expands with graphite infused right into the foam while we air seal the edges to provide the full maximum 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.

I d prefer to see a rigid material on attic kneewalls. This method of insulation won t work if the triangular attic includes ducts or plumbing pipes. But you do so at the expense of floor space. Seal all the edges penetrations and seams.

Here are the three keys to sheathing an attic kneewall properly. Cover the whole wall. 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.