Heat and Insulated Basements

Insulation Types

• Heated basements use three basic types of insulation to cover the basement walls. Batt insulation is a fiberglass blanket that is installed on interior basement walls using a wooden frame or furring strips. This type of insulation is effective and relatively easy to install yourself. Rigid foam board insulation is installed on the exterior and interior of basement walls using an adhesive. Foam board insulation usually has gypsum board or another fire-retardant material covering it. Loose-fill insulation is often used in basements that are insulated after they are finished, since you can install it without removing the drywall.

Adding Insulation

• Most climates only need enough insulation to provide an R-value of 11 for the basements walls. The type of insulation in your basement and its thickness determine how much R-value it provides. Basements with batt or loose-fill insulation usually require between 3 and 4 inches of insulation. If your home is in a cold climate or has basement walls that extend above ground level, increasing the R-value of your insulation to 19 can provide even greater energy savings.

Rim Joist

• The rim joist is the support beam between the top of the foundation wall and the subfloor. Insulating and sealing the rim joist will prevent heat loss through convection and conduction. Before you add insulation to this area, apply spray foam insulation to the gaps between your foundation wall and the rim joist to prevent cold air from infiltrating your basement. Rigid foam insulation or fiberglass batts cut to fit the space in front of the rim joist will prevent heat from escaping through the structural members of walls and basement ceiling.

Leaking Air

• Sealing the gaps in your basement ceiling and walls will prevent drafts that can suck cold air into your home. Check the places in your basement where vents, pipes, conduits and electrical fixtures penetrate the walls and ceiling of the basement. Apply spray foam insulation to any gaps around these fixtures to control the flow of air through your basement. Even small gaps can move large amounts of hot or cold air past your insulation. Walls that extend from the basement to the roof are another trouble spot that can allow conditioned air to escape if they are not properly sealed. Seal these walls to make sure that your attic vents do not draw conditioned air away from your basement.