Along with fiberglass and cellulose, foam is the most common type of insulation. Two types of foam insulation are foam board and spray foam. Foam board, typically consisting of polyurethane or polystyrene, is ideal for unfinished walls and unvented low-slope roofs. Foam spray, made of polyurethane, is ideal for adding more insulation to existing and irregularly shaped areas.
Foam Board Cost
Foam board insulation is more expensive than cellulose and fiberglass, but it's significantly less than foam spray. According to This Old House in 2011, extruded polystyrene, a commonly used rigid foam board material, costs about 50 cents per square foot for a 2-inch thickness. Rigid foam board is energy-efficient, retains its R-value and resistant to water and water vapor. Yet it is also flammable and must be covered with a fire-resistant material like gypsum or plaster.
Spray Foam Costs
Spray foam insulation is often used for smaller projects, since it costs much more than other materials. Spray foam costs about four times as much per square foot as fiberglass batts, which run around 38 cents per square foot, reports This Old House. Spray foam insulation is hard to beat when it comes to R-value. High-density spray foam insulation, which has a much higher R-value than low-density foam, is resistant to water and fire.
Foam Board Installation
While you can install foam board yourself, the website Energy Savers recommends obtaining safety instructions and detailed directions from the manufacturer beforehand. Foam board insulation is not fireproof, so you'll need to install a fireproof material such as 1/2-inch-thick gypsum wallboard.
Foam Spray Installation
Foam spray insulation requires special equipment and certification, according to Energy Savers. You should probably hire a certified professional to install the product. Although spray foam insulation may be affordable and cost-effective for small areas, higher product and installation costs may not be worth it for large projects. Ask the Builder recommends consulting an HVAC contractor to determine how much spray foam insulation will save in the long run.