Foam Board Attic Knee Wall

One of the best methods is rigid foam board with sealed joints over insulation in the knee wall.

Foam board attic knee wall. I ve seen osb oriented strand board the flaky plywood foamboard and structural or non structural cardboard sheathing materials like thermo ply. You ll need to air seal all the penetrations and leaky spots like joists under the kneewall. You can use foam board to make baffles near your soffit vents and then blow in enough insulation to reach the r value you want. Start at left or right side to install the first board using cap.

Cut boards to snugly fit from bottom to top of wall. Foam insulation boards can be attached to concrete walls as well and in such a case care should be taken not to chip the cement. When installing foam insulation boards in the attic make sure you start from one corner and work your way around the room. Boards may be used vertically or horizontally to minimize cuts.

Then you will leave the wall exposed to the attic so the radiant barrier is facing an air space the attic air space. Replace foam into the board and then tape with homesealr. 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. This method of insulation won t work if the triangular attic includes ducts or plumbing pipes.

Attic knee wall gable ends. If you want the attic to be outside then using foamboard on the attic side of the knee wall is a good idea. This is not very easy in most of the older houses we work on because the hatches and attics are too small to get rigid foam board through. I ve also seen attic kneewalls sheathed with non rigid materials mainly housewrap.

This method has you place the foil closest to the inside of the wall cavity with an air gap. Another way to install the radiant barrier on a knee wall is to do so via the cathedral ceiling method.