Building Insulation Costs

Batts and Blankets

• Most insulation comes in the form of blankets or batts. Blankets, which come in rolls, and batts, which come as precut sheets, consist of many layers of fine, woven fibers. This type of insulation is typically a few inches thick and designed to fit between the wooden studs used to frame walls or ceilings. Fiberglass insulation offers an R-value of 3 to 4 per inch and costs $0.38 per square foot as of 2013, according to This Old House. Batts made from cotton, which produces fewer itchy fibers, have an R-value of 3.7 per inch and cost $0.70 to $0.75 per square foot. Batts and blankets are best suited to new construction or for adding insulation to an unfinished attic.

Loose-Fill

• Loose-fill insulation consists of fine, loose fibers that are blown into the attic or into wall cavities. Both fiberglass and mineral wool offer an R-value of around 4 per inch, and cost between $0.19 and $0.21 per square foot as of 2013, according to This Old House. Loose-fill cellulose made from recycled newspaper costs around $0.17 per square foot and offers an R-value of 3.8 per inch. The Family Handyman estimates that you would pay $1,500 to $2,000 to add cellulose insulation to a 1,200 square-foot house as of 2012, or you could do the job yourself for $500.

Rigid Foam

• Rigid foam insulation offers a higher R-value per inch than many other types of insulation, making it an effective insulator for foundations, roofs, wall cavities and attics. Polystyrene foam sheets offer an R-value of 5 per inch and cost $0.50 per square foot for sheets measuring 2 inches thick as of 2013, according to This Old House. Polyisocyanurate boards offer an R-value of 7 to 8 per inch and cost $0.40 per square foot for a 3/4-inch thick board as of 2013.

Spray Foam

• Spray foam is one of the best options for adding insulation to finished walls without disturbing the finish. This material can be sprayed into the wall through a small hole, which is later patched to restore the look of the wall. Fine Homebuilding estimates that achieving the standard R-value of 13 in a wall cavity would cost $1.00 to $1.20 per square foot as of 2012 using open-cell spray foam, or $1.75 to $3.00 per square foot using the more efficient closed-cell spray foam. Thanks to its higher density, closed-cell spray foam has an R-value of 6.5 per inch, compared to 3.5 to 3.6 per inch for the less dense open-cell spray foam insulation.

Recommended Insulation Levels

• The North American Insulation Manufacturers Association recommends striving for an R-value of 30 to 60 in the attic, 13 to 21 in wall cavities and 13 to 30 in the floor. In general, the colder the climate, the higher the recommended R-value. For example, NAIMA recommends R-13 to R-15 insulation for wall cavities in southern Texas and much of Florida, compared to recommendations of R-13 to R-21 in northern Maine and other cold northern regions.

Financial Incentives

• Many states, cities and utility companies offer financial incentives to encourage consumers to add insulation and increase energy efficiency. These incentives, which include cash rebates, tax credits, low- or no-interest loans and utility rebates, may help you offset the cost of buying and installing insulation. The Database of State Incentives for Renewables and Efficiency can help you find incentive programs in your area.