Rigid Foam Attic Knee Wall

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.

Rigid foam attic knee wall.

October 16 2018 09 25 25 am in the next month i d like to make a project of covering the attic side of several attic knee walls actually almost all are full height walls but same principle currently fiberglass batts studs open to attic with rigid foam board in order to air seal and add a little additional r value. The bottom plate of the knee wall rests on the open floor joists and the top plate is secured against the roof deck rafters. Wondering how you can make your knee wall space insulated correctly. 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. Rigid foam insulation is innovative eye pleasing and super effective. 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. Rigid foam insulation is the solution.

The higher the knee wall the greater the amount of useful wall space you create in your finished attic. How to insulate knee walls. A knee wall is a short vertical wall roughly two or three feet high that blocks in that useless triangular space. 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. 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. 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. First you will want to add traditional insulation between the studs this can be batt insulation spray foam or even rigid foam insulation.

Fiberglass batts work best if they re enclosed and air sealed on all 6 sides. The best way to provide that sheathing is to use a rigid material. Then you can add atticfoil on top of the traditional insulation by stapling it to the wall studs.