Foam Board Attic Knee Wall

This method of insulation won t work if the triangular attic includes ducts or plumbing pipes.

Foam board attic knee wall.

Cut boards to snugly fit from bottom to top of wall. 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. You ll need to air seal all the penetrations and leaky spots like joists under the kneewall. Using foam spacers you can attach the foil behind the drywall and then stuff the remainder of the wall cavity with traditional insulation or foam board.

One of the best methods is rigid foam board with sealed joints over insulation in the knee wall. Start at left or right side to install the first board using cap. 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. Replace foam into the board and then tape with homesealr.

When installing foam insulation boards in the attic make sure you start from one corner and work your way around the room. Then you will leave the wall exposed to the attic so the radiant barrier is facing an air space the attic air space. This method has you place the foil closest to the inside of the wall cavity with an air gap. I ve seen osb oriented strand board the flaky plywood foamboard and structural or non structural cardboard sheathing materials like thermo ply.

There are as many ways to do it as there are people who do it. Boards may be used vertically or horizontally to minimize cuts. 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. If you want the attic to be outside then using foamboard on the attic side of the knee wall is a good idea.

Another way to install the radiant barrier on a knee wall is to do so via the cathedral ceiling method. The best way to provide that sheathing is to use a rigid material.