Blow-in Insulation Vs. Asbestos-Containing Material

Kimberly Sharpe

Houses built from 1930 to 1970 are likely to have asbestos in the insulation. The use of asbestos in building materials has been banned due to its likelihood of causing cancer and mesothelioma. Despite the ban on asbestos in building materials, asbestos-contaminated vermiculite was accidentally used in blown-in insulation until 1990. Comprised predominately of cellulose or silica, modern blown-in insulation does not contain asbestos; it offers a safe and energy efficient way to insulate a home.

Vermiculite Insulation

Wear gloves when touching fiberglass insulation to prevent cuts.

Vermiculite insulation has a high risk of containing asbestos. It was commonly used in blown-in insulation for attics and other home spaces from 1919 to 1990. The natural flaky material is odorless, light-weight and fire-resistant. Over 70 percent of the vermiculite used in home insulation came from a mine in Libby, Montana, according to the U.S. Environmental Protection Agency. The vermiculite from the Libby mine contained high levels of asbestos. It was not known that the vermiculite was contaminated with asbestos until 1990. The EPA warns that any home that contains vermiculite blown-in insulation is probably contaminated with asbestos.


Insulation that contains contaminated vermiculite or asbestos fibers is dangerous and should not be disturbed. The dust created by disturbing the insulation poses a serious carcinogenic and health danger. Avoid going into any attic that may contain asbestos. Avoid storing boxes or other items in the attic or near the insulation. Hire a professional asbestos removal crew to safely remove the asbestos-contaminated insulation from the home if a home renovation is planned or some other construction project must take place that could disturb the insulation.

Cellulose and Fiberglass

Blown-in insulation that was installed after 1990 poses no health risk. Cellulose blown-in insulation is comprised of 75 to 85 percent paper fibers. It also contains a fire retardant. The fire retardant is usually boric acid or ammonium sulfate. Blown-in fiberglass insulation is comprised of spun silica, which turns into glass fibers. It offers natural fire resistance. The fibers have the ability to trap air and offer insulation. Cellulose insulation tends to be thicker than fiberglass types.


Metal corrosion can occur with blown-in cellulose insulation. It requires water when blown into a home and will often retain moisture for a year or more if the home is sealed up too soon after installation. If fiberglass insulation becomes wet from a wall leak, it can begin to sag and its insulation ability will become impaired. Fiberglass insulation can also irritate and cut skin if handled. If a fire occurs, fiberglass insulation can emit toxic fumes.