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Vermiculite is a naturally occurring mineral that is or was used in many applications, including gardening to improve soil quality and as an insulation in homes. Vermiculite normally has a grayish-brown appearance and can look like small pieces of gravel. However, it is very lightweight and feels a lot like small pieces of Styrofoam. In its raw form, vermiculite is much denser than the vermiculite used as insulation, and it’s not very useful. It is made useful by undergoing a process called exfoliation. This is done by heating the vermiculite to a temperature of about 1000° Celsius. The heat causes it to expand (similar to the popping of popcorn). In this expanded condition it is useful for several purposes – including as insulation in a home’s attic. It works well as insulation because it conducts heat very poorly. Vermiculite insulation was often sold under the name “Zonolite.”

vermiculite insulation

Typical Vermiculite Insulation

Is Vermiculite Insulation Dangerous? Does Vermiculite Contain Asbestos?

Pure vermiculite is totally safe. The problem is that the majority of the vermiculite used in the United States came from mines in or near Libby, Montana. The reason the Libby vermiculite is dangerous is due to the proximity of the vermiculite mine and a mine containing asbestos. In other words, most of the Libby vermiculite is contaminated with cancer-causing asbestos fibers. The approximately 25% of vermiculite insulation used in the United States that did not come from Libby is perfectly safe.

What Should You Do If You Have Vermiculite Insulation?

Fortunately, no one spends much time in their attic. Here are three things to keep in mind if you have vermiculite insulation in your attic.

  1. Most people who contract asbestos-related diseases have been exposed to asbestos for long periods of time – often for years.
  2. Very little of the air in our homes come into our home from our attic.
  3. Normally, if left undisturbed, the asbestos fibers in the vermiculite insulation do not become airborne.

Based on these three facts, often the best thing to do is to leave the insulation undisturbed. If you are going to be doing some home renovations, such as working in the attic or removing/replacing a ceiling, then this will likely cause some of the insulation to be disturbed, and some of the asbestos fibers to become airborne. Depending on the extent of the renovations, disturbance of the vermiculite, etc. it is certainly possible for some of the asbestos in the insulation to enter into the living space of your home. Therefore, for any such work, you definitely need to take precautions. If you think or know that you have vermiculite insulation in your attic, and are concerned about its possible effects on the health of those living in your home, my advice is for you to contact an asbestos inspection company.

Read one of our most-read posts, Grounded and Ungrounded Outlets

© 2020 Mike Morgan

This article was written by Mike Morgan, owner of Morgan Inspection Services. Morgan Inspection Services has been providing home, septic, and well inspection services throughout the central Texas area since 2002. He can be reached at 325-998-4663 or at No article, or portion thereof, may be reproduced or copied without prior written consent of Mike Morgan.

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