How To Insulate A Knee Wall Attic

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How to insulate a knee wall attic.

Install a top and bottom plate or blocking at the top and bottom of all knee wall cavities. Knee walls leak heat in at least 2 ways. Bring the attic inside insulating between the rafters simplifies the air sealing details. Air sealing and insulating the knee wall can make the attic space warmer more efficient and more comfortable.

The specific r value for the insulation you need. Keep the attic outside insulating a kneewall and the attic floor behind the kneewall is possible but tricky. How to insulate knee walls 1. Then either fiberglass batts secured in place or netted cellulose is used to fill the rafter cavities.

Use an r value map to determine the amount of insulation you need. Behind the knee wall install batts between the ceiling joists taking care not to block soffit vents and. Install an air barrier on the exterior of attic knee wall insulation and to block open floor joist cavities under attic knee walls. Install insulation without misalignments compressions gaps or voids in all knee wall cavities.

The other is spraying at least 2 of closed cell spray foam directly onto the roof deck encapsulating the rafters. This is the obvious part especially if there is no insulation in them. The floor of the room with the knee wall is typically connected to the attic. In this case after insulating the stud cavities with fiberglass batts use 1 inch minimum rigid foam insulation to cover the back of the knee wall which will prevent attic air from circulating around and through the insulation.

Lay each unfaced strip of insulation between the. Cut unfaced batt insulation to fit between the floor joists in the space behind the knee wall. Be sure to notch the rigid foam over the floor joists and run it all the way down to the drywall or plaster or tuck separate 2 by or foam board blocks between the joists to provide air stops in the joist bays and seal all gaps with canned foam or caulking.