Importance of Proper Attic Insulation

Insulation is measured in R-values—the higher the R-value, the better your walls and roof will resist the transfer of heat. Click Here for Standardized R-Value’s per material. DOE recommends ranges of R-values based on local heating and cooling costs and climate conditions in different areas of the nation. The map and chart below show the DOE recommendations for your area. State and local codes in some parts of the country may require lower R-values than the DOE recommendations, which are based on cost effectiveness.

Although insulation can be made from a variety of materials, it usually comes in four types; each type has different characteristics.

Rolls and batts—or blankets—are flexible products made from mineral fibers, such as fiberglass and rock wool. They are available in widths suited to standard spacings of wall studs and attic or floor joists: 2x4 walls can hold R-13 or R-15 batts; 2x6 walls can have R-19 or R-21 products.

Loose-fill insulation—usually made of fiberglass, rock wool, or cellulose—comes in shreds, granules, or nodules. These small particles should be blown into spaces using special pneumatic equipment. The blown-in material conforms readily to building cavities and attics. Therefore, loose-fill insulation is well suited for places where it is difficult to install other types of insulation.

Rigid foam insulation—foam insulation typically is more expensive than fiber insulation. But it's very effective in buildings with space limitations and where higher R-values are needed. Foam insulation R-values range from R-4 to R-6.5 per inch of thickness (2.54 cm), which is up to 2 times greater than most other insulating materials of the same thickness.

Foam-in-place insulation—can be blown into walls and reduces air leakage.

Insulation Tips

• Consider factors such as your climate, building design, and budget when selecting insulation R-values for your home.
   
• Use higher density insulation, such as rigid foam boards, in cathedral ceilings and on exterior walls.
   
• Ventilation plays a large role in providing moisture control and reducing summer cooling bills. Attic vents can be installed along the entire ceiling cavity to help ensure proper airflow from the soffit to the attic to make a home more comfortable and energy efficient. Check with a qualified contractor.
   
• Recessed light fixtures can be a major source of heat loss, but you need to be careful how close you place insulation next to a fixture unless it is marked IC—designed for direct insulation contact. Check your local building codes for recommendations.
   
• As specified on the product packaging, follow the product instructions on installation and wear the proper protective gear when installing insulation.
   
• $ Long-Term Savings Tip: One of the most cost-effective ways to make your home more comfortable year-round is to add insulation to your attic.

• Adding insulation to the attic is relatively easy and very cost effective. To find out if you have enough attic insulation, measure the thickness of the insulation. If it is less than R-22 (7 inches of fiber glass or rock wool or 6 inches of cellulose), you could probably benefit by adding more. Most U.S. homes should have between R-22 and R-49 insulation in the attic.

If your attic has enough insulation and your home still feels drafty and cold in the winter or too warm in the summer, chances are you need to add insulation to the exterior walls as well. This is a more expensive measure that usually requires a contractor, but it may be worth the cost if you live in a very hot or cold climate.

You may also need to add insulation to your crawl space. Either the walls or the floor above the crawl space should be insulated.

U.S. Department of Energy Recommended* Total R-Values for New Houses in Six Climate Zones
How Much Insulation Does My Home Need?

* These recommendations are cost-effective levels of insulation based on the best available information on local fuel and materials costs and weather conditions. Consequently, the levels may differ from current local building codes. In addition, the apparent fragmentation of the recommendations is an artifact of these data and should not be considered absolute minimum requirements.