Insulating A Finished Attic With Knee Walls
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2d extend insulation into joist space to reduce air flows.
Insulating a finished attic with knee walls. Although kneewalls can help turn attics into living space they often present insulation challenges most builders install fiberglass batts between the studs and some type of blown insulation between the floor joists. In finished attic rooms with or without dormer insulate 2a between the studs of knee walls 2b between the studs and rafters of exterior walls and roof 2c and ceilings with cold spaces above. We reduced the air leakage nearly 50 on this house in shaker heights without insulating the walls. Blown insulation in the knee wall and top attics.
There are two basic ways to insulate a finished attic. Insulate across the top of flat attic. How to insulate knee walls. 1a attic access door.
We prefer cellulose but we use fiberglass sometimes too. Insulating the floor and kneewall requires more careful air sealing but is sometimes easier to insulate since you can use blown insulation. 1000 2000 cfm50 reductions are fairly common with this method. Added bonus the floor of this knee wall leaked too so there is a line of foam just above the floor joist.
Knee walls are half walls built into areas where a full sized wall will not fit such as finished attic crawlspaces. In this case the area behind the knee wall will be uncomfortably hot or cold. Unlike traditional walls with two finished sides. If only the living space will be insulated wrap the insulation around the room s walls and ceiling and then continue along the floor of the non living space.
If you want the attic to be outside then using foamboard on the attic side of the knee wall is a good idea. 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.