Vinyl Siding Insulation Guide

Insulated Vinyl Siding

• Insulated vinyl siding is manufactured by permanently attaching foam insulation to the back of regular vinyl siding to make it more energy efficient. The National Association of Home Builders Research Center says the cost of insulated vinyl siding is comparable to non-insulated vinyl siding used with ¾-inch foam sheathing. Because insulated vinyl siding is more rigid, it’s easier to install and doesn’t sag like regular vinyl siding can. The R-value of insulated vinyl siding ranges from around R-3.65 to R-5.

Foam Board

• Foam board insulation usually comes in 4-by-8-foot sheets that can be cut to size with a small handsaw or utility knife. Thickness ranges from ½ inch to 4 inches. Foam board insulation is easier to work with than fiberglass and doesn’t cause itching or other allergic reactions. It can be cut to fit irregular shapes and can be installed with glue or nails instead of staples. Foam board insulation is damaged by exposure to the sun, and it also absorbs water vapor, so it’s important keep it covered until you’re ready to install it. R-values of foam board vary, but range from R-3.8 to R-4.4 per inch of thickness.

Backerboard

• Backerboard is an insulation board that’s placed over the original siding so you’ll have a flat surface to attach the new vinyl siding to. Using the drop-in type of backerboard may cause your vinyl siding to bulge or ripple by flattening the built-in contour of the panels. In addition, although it’s called an insulation board, backerboard isn’t very energy efficient. It can also cause moisture damage to the original wood by trapping moisture inside. One type of drop-in style that is effective is contoured foam underlayment because it’s computer engineered to fit the particular siding you’re installing. Using contoured foam underlayment increases the R-value of outside walls by R-2.8 to R-3.3.

Fan-Fold

• Fan-fold foam insulation can be used when you’re installing vinyl siding over existing clapboard. This type of insulation comes in sheets that are 4 feet tall and 50 feet long. The foam ranges from ¼ to ⅜ inch thick. Fan-fold insulation only has an R-value of 1, so it doesn’t do much in the way of insulating your home. Its main purpose is to help the vinyl siding lie flat.