Rigid Foam Attic Knee Wall

The bottom plate of the knee wall rests on the open floor joists and the top plate is secured against the roof deck rafters.

Rigid foam attic knee wall.

Rigid foam insulation is the solution. Georgia recognized this problem about a decade ago and started requiring all attic kneewalls to have sheathing on the attic side and to be insulated to at least r 18. It easily expands with graphite infused right into the foam while we air seal the edges to provide the full maximum insulation. The higher the knee wall the greater the amount of useful wall space you create in your finished attic.

Rigid foam insulation has a radiant barrier on both sides so it reflects roof heat out in the summer but brings the heat back in during the cold winter. A knee wall is a short vertical wall roughly two or three feet high that blocks in that useless triangular space. 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. 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.

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. Adding rigid foam insulation to attic side of knee walls on. 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 insulation is innovative eye pleasing and super effective.

How to insulate knee walls. Adding a rigid foam air barrier to the cold side of the batt is a great way to take care of this issue on a knee wall between finished and unfinished attic space. But you do so at the expense of floor space. Knee walls are the bane of energy and comfort in homes by which i mean they are vertical half height walls built to convert normally unconditioned attic into liveable space.

Wondering how you can make your knee wall space insulated correctly. Fiberglass batts work best if they re enclosed and air sealed on all 6 sides. This method of insulation won t work if the triangular attic includes ducts or plumbing pipes.