How Thick Should Cellulose Insulation Be for an Attic?

Identification

• Loose-fill insulation is made from tiny bits of fiber or foam particles. Cellulose insulation is commonly placed in attics. This insulation is made from recycled newspapers. The R-value of cellulose insulation is 3.28 to 3.8 per inch. According to the United States Department of Energy, the R-value is a measurement used to determine the ability to resist heat flow. The higher the R-value an insulation has, the more effectively it will work. R-38 insulation is recommended for use in residential homes. To achieve R-38, you will need 10 to 12 inches in thickness of cellulose insulation.

Installation

• Loose-fill cellulose insulation must be blown into your attic using special equipment. Most installers use the two-hole method, which requires drilling holes in between the exterior walls. Cellulose insulation may also be blown in through holes in the ceiling, by drilling holes between the rafters of your home. Loose-fill insulation is most effective when installed correctly. Most homeowners hire a professional contractor to perform this task. If you wish to do it yourself, be sure to follow all instructions on your insulation and check you local fire codes. Installing loose-fill cellulose insulation will require equipment rentals, as well.

Considerations

• Loose-fill insulation may lose its effectiveness over time because of settling, especially in closed attic spaces. Cellulose settles more often than other loose-fill insulation such as fiberglass. When placing cellulose in your attic, you must install at least 20 percent more insulation to offset settling. The Department of Energy recommends homeowners use one 30-pound bag of cellulose for every three wall cavities filled for optimal thickness.

Safety Measures

• Cellulose insulation in your attic should cover the wall to the top plates. Avoid covering the eaves with insulation, as this interferes with attic ventilation. Be sure to keep insulation at least 3 inches away from lights and electrical devices. Seal all of the duct work inside your attic to prevent insulation from being distributed throughout your home.