Insulating Knee Wall Floor

Remember to seal air leaks at any electrical boxes in the kneewall and ceiling below the insulated floor.

Insulating knee wall floor.

Another alternative for knee walls conditions is to remove and reinstall the batt insulation to qii standards. An insulated kneewall is effectively an exterior wall so you ll need a layer of rigid foam drywall osb or thermoply on the back side of the kneewall to prevent cold air from degrading the performance of the insulation. Unlike traditional walls with two finished sides the rear of a knee wall is often a triangular piece of attic space where the roof tapers to meet the floor. This approach involves wrapping the wall cavities with 1 sheetrock on the interior and 2 foil backed foam insulation board on the exterior.

Added bonus the floor of this knee wall leaked too so there is a line of foam just above the floor joist. I also filled in the space between the first and second floor the full length of the knee wall floor. Insulating this space inside the knee. Blown insulation in the knee wall and top attics.

Between the cavities fiberglass or cellulose insulation is blown in creating a tight thermal envelope for the bonus room. It is important to choose an air barrier and insulation material that will reduce the air leakage and heat loss as much as possible. Properly sealing and insulating attic knee walls can significantly reduce air leakage and heat loss between the conditioned space and the unfinished 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.

Insulation itself does not stop air flow. Then cover that same area with an r 8 fsk affixing it using cap nails. Not only are air leaks common in these areas but they are frequently not insulated properly. In tight attics or odd shaped wall conditions i e.

The knee wall is the short wall that reaches from the sloped ceiling to the floor or connects the upper ceiling to the lower ceiling inside the attic. I then installed polystyrene using grip caps to cover the entire area. We prefer cellulose but we use fiberglass sometimes too. This also enabled me to air seal the entire area by using foil tape on all the seams and great stuff foam seal.

Insulating and air sealing knee walls vented version if you choose to insulate along the horizontal and vertical walls you have four key air sealing points. We reduced the air leakage nearly 50 on this house in shaker heights without insulating the walls. The ceiling and knee wall drywall will act as your air barrier.