You ve added yet another nail in the coffin of the archaic kraft facing retarder barrier system.
Batts which direction attic knee wall.
You can see the image below for an example of a knee wall.
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.
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.
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.
Installation instructions tthis section provides info on how to install insulation it contains specific information on installation details for wall and knee wall insulation that will assist with proper installation to meet resnet grade 1 criteria for fiberglass and mineral wool batt insulation.
In this energy smart details article senior editor martin holladay describes two ways to insulate attic kneewalls.
Kneewalls are commonly found in attics especially in attics that have been converted to living space but they can be difficult to insulate properly.
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.
I ve got some kneewalls that i d like to beef up.
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.
1000 2000 cfm50 reductions are fairly common with this method.
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.
Wall and knee wall insulation.
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.
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.
Install insulation without misalignments compressions gaps or voids in all knee wall cavities.
Install an air barrier on the exterior of attic knee wall insulation and to block open floor joist cavities under attic knee walls.
Despite all the bad publicity reflective insulation is getting lately i like to use it quite a bit on knee walls.
