Vermiculite Insulation: Asbestos Inside?

jmatuella asks,

I have a 1938 tudor home. The attic has been converted to our master bedroom. Behind the knee walls is where vermiculite insulation lays. I'm not sure If I need to get this out of the house because of the potential asbestos exposer. Or can I put fiberglass insulation or blown-in insulation over the top of it?

Our Answer

The Environmental Protection Agency (EPA) reports that Vermiculite is a naturally occurring mineral composed of shiny flakes, resembling mica. When heated to a high temperature, flakes of vermiculite expand as much as 8-30 times their original size. The expanded vermiculite is a light-weight, fire-resistant, and odorless material and has been used in numerous products, including insulation for attics and walls. A mine near Libby, Montana, was the source of over 70 percent of all vermiculite sold in the U.S. from 1919 to 1990.

You should assume that vermiculite insulation contains asbestos and not disturb it. While you can hire a trained professional to test your attic for asbestos, this may be expensive and, depending on the methods used, might give you erroneous results. The EPA recommends that you assume the vermiculite contains asbestos and hire a professional to have it properly removed.

You can get more info here: http://www.epa.gov/asbestos/pubs/verm_questions.html.