Can I Use Insulated Sheathing on Interior Walls?

Interior Uses

• Insulated sheathing is the first choice for insulating interior masonry walls, such as exposed brick or concrete in a basement. Attach furring strips to the wall, then staple the insulation sheets to the furring strips. You can cover the sheathing with paneling or wallboard, or, in a basement or crawl space, leave the sheathing exposed. You can also use insulated sheathing in attics, attaching it to the underside of the roof where it will block heat and cold from entering or leaving the attic.

Characteristics

• You can choose from several different types of insulation sheathing, including molded expanded polystyrene foam board (MEPS), extruded expanded polystyrene foam board (XEPS) and polyisocyanurate and polyurethane foam board. MEPS is the least expensive form of insulation sheathing and the others are slightly more expensive. Each comes in different R-values and is available with or without foil facings.

Benefits

• Insulated sheathing provides superior R-value in a small space. R-value is a measure of how well the insulation blocks heat transfer. The higher the R-value, the better the insulation. Styrofoam sheets have R-values of 3.8 to 8 per inch of thickness, compared to 3.2 per inch for fiberglass batts. The foam board is easy to cut with a utility knife, so it's easier than batts to fit around electrical outlets and lights and in odd corners.

Disadvantages

• Insulated sheathing is one of the most expensive insulation materials. Green Econometrics research group has computed that rigid insulation sheathing costs about 70 cents per square foot, compared to fiberglass batts that cost about 40 cents per square foot. When you install insulated sheathing, you have to shield it from moisture and damage from punctures, which means covering it in some way for any applications in high-traffic areas. So it's not practical to install it in most existing homes unless you're working in unfinished attics or basements.