Insulating the “envelope” of your home—its outer walls, ceiling, windows, doors, and floors—is often the most cost-effective way to improve energy efficiency and comfort.
A homeowner can save up to 20 percent on heating and cooling costs by sealing and insulating, according to estimates from the U.S. Department of Energy.
Homeowners can choose from a lot of materials and price ranges. When shopping, consider R-value, airflow, and density.Here’s a quick guide:
Insulation’s ability to slow the transfer of heat is measured in R-values. The higher the R-value, the better the insulation material’s ability to resist the flow of heat through it.
First, check the insulation in your attic, ceilings, exterior and basement walls, floors, and crawlspaces to see if it meets recommended levels.
To assess your attic insulation, measure the thickness of the insulation, and decide what type of insulation you have. If you’re not sure, take a small sample to your building supply store or your local electric co-op to ask for help in identifying it.
The effectiveness of insulation is measured in R-value per inch. The total R-value of your insulation depends both on its type and its depth. To determine the total R-value of your insulation, decide what type of insulation is installed, and multiply the R-value per inch times the number of inches installed. Cellulose loose-fill insulation, for example, is rated at about R-3.5 per inch. If your attic has 4 inches of cellulose, that’s 3.5 x 4 = R-14.
If it is less than R-22 (7 inches of fiberglass or rock wool or 6 inches of cellulose), you could probably benefit by adding more. Most Kentucky homes should have between R-38 and R-60 insulation in the attic and R-25 to R-30 in the floor.
Although you often hear the amount of insulation quoted in inches of thickness, the true measure of insulation is its final installed R-value. The insulation properties of various materials vary significantly, so the inches installed does not really tell you much. In addition to the material itself, the quality of the installation job (minimizing voids) is important for the maximum savings.
Your local insulation contractor, co-op energy advisor, or building inspector can advise you about the recommended amounts of insulation, or visit www.doe.gov.
Building scientists across the nation are beginning to use a different vocabulary when talking about the performance of insulation. More emphasis is being given to the insulation’s resistance to airflow.
Thermal bypass, or the movement of heat around or through insulation, frequently occurs due to missing air barriers or gaps between the air barriers and the insulation.
In terms of resistance to airflow, fiberglass is the least resistant, wet-blown cellulose is next, then dense-pack cellulose, and spray foams are the best.
The third determining factor is density. Denser insulation products have more fibers per square inch and, therefore, give you greater insulating power through higher R-values.
For the walls in your new room, consider batt insulation if you are doing the insulating job yourself.
Sprayed-on urethane foam insulation offers the highest insulation levels for limited space inside a framed wall. Closed-cell foams are best because they form their own vapor barrier. Another option is blown-in fiberglass or mineral wool mixed with a resin material.
For both new and existing walls, adding rigid foam board insulation to the exterior is best.
For a detailed discussion on specific types of insulation, visit the Internet energy efficiency page of the U.S. Department of Energy at: apps1.eere.energy.gov/consumer/your_home.