What is the Purpose of Home Insulation?

Adding insulation to your home can be one of the fastest and most cost-effective ways to reduce energy costs. Proper insulation protects a home from outside hot or cold temperatures and air leaks and controls moisture. You can increase the comfort of your home while reducing your heating and cooling needs by investing in proper insulation and sealing air leaks.


Although insulation can be made from a variety of materials, it usually comes in four types. Each type has different characteristics. What follows is a comparison of each different type of home insulation.

Batts and blankets: 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.

Rigid insulation: Made from fibrous materials or plastic foams pressed or extruded into board-like forms. This type of insulation provides thermal and acoustic insulation, added structural strength, and air sealing. Rigid insulation is commonly used in exterior walls under the siding and along the rim joist. Rigid foam insulation used in interior living spaces must be covered with finishing material (usually drywall) for fire safety.

Loose-fill insulation: Usually made of fiberglass, rock wool, or cellulose in the form of loose fibers or fiber pellets. It is blown into spaces using special equipment, and the blown-in material conforms readily to building cavities and attics. Sometimes loose-fill fibers are sprayed with an adhesive or water to cover irregularly shaped and hard-to-reach areas. This technique is often used with cellulose insulation and is called wet spray. The insulation dries within a few days and is resistant to settling.

Foam-in-place insulation: Foams can be sprayed into open wall cavities, where they expand to fill the space and provide air sealing and insulation. Spray foams are particularly helpful for insulating difficult areas and are available in open or closed cell. Open-cell allows water vapor to move through more easily than closed-cell. Closed-cell foam is typically more costly than open-cell but is more energy-efficient.


Home insulation is rated in terms of thermal resistance, called R-values. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness, and its density.

Depending on what region of the country you live in and the age of your home, the amount of insulation you’ll need may vary.

To determine what type and how much insulation you need, inspect your insulation to determine if it meets the levels recommended for your area. Most often, for exterior walls, it is recommended that you use R-13 to R-30 insulation. For attics and ceilings, R-30, R-38, and R-49 are recommended. That being said, before you begin your DIY project, be sure to check EnergyStar’s R-Value map to determine how much insulation you may need.


When beginning a home insulation project, you must consider a few things before you start. Here are some DIY tips for insulating your home in the best way possible.

• 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, on exterior walls, in cathedral ceilings, and on exterior walls.
• Recessed light fixtures can be a major source of heat loss, but you must be careful how close you place insulation next to a fixture unless it is marked IC. This means it is designed for direct insulation contact. Check your local building codes for recommendations.
• Always follow the product instructions for installation and wear the proper protective gear when installing home insulation.

To find out more about how to choose and install the correct insulation for your home, visit the U.S. Department of Energy.