Foam board insulation is a rigid polystyrene product that is available in varying thicknesses and density. Foam board is particularly effective when used on exterior walls to control heat gain and loss. The thermal resistance (R-value) of foam board offers insulation and acts as a vapor retarder when installed on walls and covered with drywall or paneling. Proper sealing of areas around wires, pipes or vents that leak outside air into the home increases the effectiveness of the insulation qualities of foam board insulation.
Wall Preparation
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Prepare walls for installation of foam board insulation by removing dust and dirt with a vacuum, or wipe the walls down with rags. Remove any blobs of paint, and smooth out any spots that are very rough by scraping or sanding. Allow concrete walls the proper time to cure and dry if the walls are new construction. Repair any water leaks in the walls.
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Choosing Adhesives
Adhesives for gluing foam board insulation on walls are available in spray-on and in tubes for use in caulking guns. Water-based and petroleum-based adhesives are widely available. When purchasing adhesives, check the labels for high-strength bonding and low fume emissions. Not all adhesives are designed for foam board insulation; some will damage the foam board or will not properly adhere.
Gluing Foam Board Insulation
The ideal temperature for gluing foam board insulation is between 40 and 90 degrees Fahrenheit. Foam board insulation requires 24 hours to acclimate to the temperature of the area where it will be installed.
Install foam board insulation either vertically or horizontally. Installing vertically shortens the time the foam board must be held in place for the adhesive to bond.
Do any necessary trimming of the foam board before applying adhesive. The adhesive is applied four inches in from each vertical edge and to the center. The continuous beads of adhesive are ¼" in depth and applied in a zigzag pattern. Hold the foam board insulation in place for a few minutes to allow the adhesive to bond to the wall. Apply a waterproof tape to the seams to seal them.
Foam board insulation is flammable and must be covered with drywall or paneling. Glued foam board insulation should be allowed to dry for 24 hours before installing drywall or paneling.