Like this post? Share it!

What is Vermiculite?

Vermiculite is a naturally-occurring mineral that is used in many applications. It was used in other applications, but some of those uses have been discontinued for safety reasons. It is still used in some applications such as gardening (to improve soil quality). One of its primary uses for many years was as an insulation in homes.

Vermiculite normally has a grayish-brown or silver-gold color. It also often has a shiny appearance like the mineral mica. It can be as small as a BB or almost an inch in length. Most often it is about the size of small pieces of gravel. In its useful form, vermiculite is very lightweight and feels a lot like small pieces of Styrofoam.

In its raw form, vermiculite is much denser than the vermiculite that is used as insulation. Vermiculite is not very useful in its raw form. 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). When vermiculite is exfoliated, it expands about 10 to 30 times its original size.

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. The fact that it does not burn was another characteristic that made Vermiculite “safe” to use as an insulation in homes since it would not catch fire and aid in the spread of a home fire.

vermiculite insulation
vermiculite insulation in attic

Typical Vermiculite Insulation

What is Zonolite?

Zonolite was the trademarked name of some of the vermiculite insulation that was sold between about 1940 and 1990. It was manufactured by the W.R. Grace Company. Zonolite is asbestos contaminated and has all the risks associated with vermiculite insulation that are discussed in this article.

Is vermiculite insulation dangerous? Does Vermiculite contain asbestos?

Pure vermiculite is totally safe. The problem with it is that the majority of the vermiculite insulation used in the United States came from mines in or near Libby, Montana. The reason that the Libby-mined vermiculite is dangerous is because the ore in the Libby mine also contains asbestos. This means that almost all of the Libby vermiculite is contaminated with cancer-causing asbestos fibers. The vermiculite that is produced and used today for various purposes does not come from the mine in Libby, and it is believed to be asbestos-free.

The approximately 25% – 30% of vermiculite insulation used in the United States that did not come from Libby is perfectly safe. The problem, if you have it in your home, is that you do not know where it was mined. Since as much as 75% of all vermiculite insulation contains asbestos, it is best to assume that all vermiculite insulation contains asbestos and to take the necessary precautions if you have vermiculite insulation in your home.

If you have vermiculite insulation in your home, it is best to assume that it contains asbestos, and to take the necessary precautions.

When was Vermiculite Insulation Installed in homes?

Vermiculite was mined and installed in many homes starting in 1919. It stopped being used in 1990 after it was determined to be dangerous. In 1985 the Environmental Protection Agency (EPA) estimated that 940,000 homes in the US contained vermiculite (Zonolite) attic insulation.

How to Know if you have Vermiculite Insulation in Your Home?

Look at the photos on this site, and if you have something similar in your attic, then it is likely that it is vermiculite. Asbestos fibers are very small and cannot be seen/identified with the naked eye, so you cannot determine if the insulation contains asbestos simply by looking at it. If you suspect that you have vermiculite, do not touch it or disturb it. Disturbing the insulation can cause the asbestos fibers to become airborne, allowing you or others to inhale them.

It is not uncommon at some point in the past, that newer insulation was installed over the top of the insulation that was originally installed in your attic. My advice is that if you don’t see anything that looks like the photos of vermiculite on this and other sites, then don’t go digging around in your attic for it, because it is safest if it is not disturbed. If you are determined to find out if you have vermiculite, then I highly recommend taking all necessary precautions including wearing an appropriate mask before you start digging around in your insulation.

What Should you do if you have Vermiculite Insulation?

Fortunately, no one spends much time in their attic so, under normal conditions, the risk of inhaling the asbestos fibers is pretty low. 

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 times – often for years.
  2. Very little of the air in our homes comes into our home from the attic, so even if some of the asbestos fibers in the attic insulation become airborne, the probability of the fibers entering the living area of the home is low.
  3. Normally, if left undisturbed, the asbestos fibers in the vermiculite insulation will not become airborne.

Here are some recommendations that you should consider if you have vermiculite insulation in your attic.

  1. Normally, the safest thing to do is to leave the vermiculite insulation undisturbed.
  2. Do not store things in your attic because doing so can disturb the insulation. The stored items can also become contaminated and carry some asbestos fibers into your home when the item is brought back into the house.
  3. Minimize time spent in the attic for whatever purpose.
  4. DO NOT remove the insulation yourself.
  5. Post a sign at the attic entrance stating something such as “CAUTION: Attic insulation contains asbestos. DO NOT disturb the insulation.” This sign will help to protect family members who may enter the attic as well as electricians, plumbers, satellite dish installers, and others who may enter the attic to do work.
  6. Contact a licensed asbestos remediation company prior to starting any renovation that would significantly disturb the insulation, or that would open up a ceiling or wall that could contain vermiculite insulation in it. (More on this below.)

What Should You do if You have Vermiculite Insulation and are Planning Renovations?

If you are going to be doing some home renovations, you must take into account the risk of the asbestos in the vermiculite insulation. Another thing to think about is that if there is vermiculite insulation in your attic, then it is also possible that vermiculite insulation is also inside the exterior walls. If your renovations will include things such as working in the attic or opening up a portion of a ceiling or an exterior wall, then you must take appropriate precautions. Precautions are required because of the likelihood of disturbing the insulation which will cause some of the asbestos fibers to become airborne.

Depending on the extent of the renovations that you are planning, you will possibly disturb the vermiculite insulation. If you are doing something that will disturb the insulation, and you are opening a ceiling or an exterior wall, then it is highly likely that some of the asbestos in the disturbed insulation will enter into the living space of your home.

If you know or suspect that you have vermiculite insulation in your attic or walls, then you should contact an asbestos consulting/remediation company prior to starting any work that would open up a ceiling or exterior wall or that would significantly disturb the insulation.

If you think or know that you have vermiculite insulation in your attic, and are concerned about it’s possible effects on the health of those living in your home, my advice is for you to contact an asbestos inspection company.

Read another popular post, What is Expansive Soil?

© 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.

Like this post? Share it!

Subscribe to HouseWorks Blog

Success! You will now receive emails from House Works

There was an error while trying to send your request. Please try again.

will use the information you provide on this form to be in touch with you and to provide updates and marketing.