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.
Batts which direction attic knee wall.
Knee walls are short usually wooden walls installed around the sides of an attic where the rafters meet the floor.
You ve added yet another nail in the coffin of the archaic kraft facing retarder barrier system.
1000 2000 cfm50 reductions are fairly common with this method.
Despite all the bad publicity reflective insulation is getting lately i like to use it quite a bit on knee walls.
Install a top and bottom plate or blocking at the top and bottom of all knee wall cavities.
I ve got some kneewalls that i d like to beef up.
Install insulation without misalignments compressions gaps or voids in all knee wall cavities.
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.
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.
But just in case anyone still buys and uses faced batts i ll add two additional comments.
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.
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.
However if you are in a cold climate then adding radiant barrier to the attic side of the knee wall will help the room retain heat in the winter.
Install an air barrier on the exterior of attic knee wall insulation and to block open floor joist cavities under attic knee walls.
You can see the image below for an example of a 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.
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.
