Insulating only the attic roof rafters and the walls at the end of the attic is one method some use to insulate the knee wall area underneath but carson dunlop author of principles of home.
Insulate attic knee walls.
Knee walls are found in many older houses where the ceiling on the top floor is an attic or.
A better approach is to insulate the roof slope above the attic.
If you re insulating an attic the knee walls are important.
The best materials for the attic and thus the knee wall are spray foam fiberglass and cellulose.
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.
This method can be made to work but the necessary air sealing details are demanding and fussy.
One of the best methods is rigid foam board with sealed joints over insulation in the knee wall.
There are two ways to insulate triangular attics behind kneewalls.
Insulating knee walls other spaces in the attic.
If you plan to insulate the roof deck of your attic then you would use spray foam or fiberglass batts.
They are short walls usually no more than 3 feet high used to support the rafters in roof construction with attic space behind them.