Batts Which Direction Attic Knee Wall

Install insulation without misalignments compressions gaps or voids in all knee wall cavities.

Batts which direction attic knee wall.

The shortest distance from the top of the knee wall to the top of the outside wall beneath is still along the roof line and you avoid having to insulate the floor behind the knee wall. Despite all the bad publicity reflective insulation is getting lately i like to use it quite a bit on knee walls. In this energy smart details article senior editor martin holladay describes two ways to insulate attic kneewalls. A job we finished last week dropped from 4060 to 2150 cfm50 just with knee wall air sealing we were able to get 8 of one wall that had no top plate.

Kneewalls are commonly found in attics especially in attics that have been converted to living space but they can be difficult to insulate properly. Allison your comments about the irrelevance of the location of kraft facing on fiberglass batts are spot on and for all the reasons you iterate. There are arguments about shingle life over a hot roof vs vented but shingle color is more significant and as already stated one can install ventilation chutes. Install an air barrier on the exterior of attic knee wall insulation and to block open floor joist cavities under attic knee walls.

Knee walls are short usually wooden walls installed around the sides of an attic where the rafters meet the floor. They are 2 4 construction kraft faced r 11 batts in the wall with the paper facing the drywall and a plastic vapor barrier in the knee wall attic. If i place vertical runs of r 30 unfaced against the current plastic barrier i d use a perforated barrier to hold them in place. But just in case anyone still buys and uses faced batts i ll add two additional comments.

Install a top and bottom plate or blocking at the top and bottom of all knee wall cavities. In most instances they are no taller than 3 feet but some builders may custom fit them according to the roof s shape and size. If the knee walls are sharing space with an attic that already has radiant barrier on the rafters then the room on the other side of the knee wall is already benefiting from not gaining heat. You can see the image below for an example of a knee wall.

You ve added yet another nail in the coffin of the archaic kraft facing retarder barrier system. I ve got some kneewalls that i d like to beef up. 1000 2000 cfm50 reductions are fairly common with this method.