Boosting attic insulation gives you the most value for your dollar. The U.S. Department of Energy recommends attic insulation with an R-value of 22 to 49 in most houses. To check your insulation, measure the thickness. Seven inches of fiberglass or rock wool insulation and six inches of cellulose insulation are equal to an R-value of 22. In all but the mildest climates, the agency recommends adding more.
Adding insulation can cost up to $1,800 and could reduce your heating and cooling bills by more than $100 a year. If it is less than seven inches, you may need to add more. Also check to see if there is a vapor barrier under the insulation. Vapor barriers such as Kraft paper, tarpaper and plastic sheeting prevent moisture from entering the attic through the house below. If there is no vapor barrier, you may want to paint the home's ceilings with a vapor barrier paint to reduce potential moisture damage to the attic.