What is Vermiculite Insulation?

Vermiculite insulation is found in many homes in our service area. This type of insulation may contain asbestos as it can be a hazard for an unsuspecting homeowner. In this post I would like to discuss the hazards, what types of remediation techniques are available and some resources for further information/research.

What is Vermiculite insulation?

Vermiculite is a naturally occurring mineral composed of shiny flakes that resemble mica. When heated rapidly to a high temperature the crystalline mineral expands into low density accordion like strands. In this form it is a lightweight fire resistant material that was largely used as insulation in attics and walls.

Vermiculite forms over time by the weathering of the mineral biotite. Unfortunately, biotite deposits are often in close proximity to deposits of diopside, which transform into asbestos due to the same weathering processes that create vermiculite.

Exposure to asbestos can cause lung cancer, mesothelioma, and scarring of the lungs known as asbestosis. The risk of contracting these diseases increases in the intensity and length of exposure to asbestos. Smokers have and increased risk of lung cancer.

The largest vermiculite mine was started in Libby, Montana in the 1920’s. Although it was known that the vermiculite there was contaminated with tremolite, a highly toxic form of asbestos, the mine continued to operate until stiffer environmental controls finally forced it to close in 1990. By this time, the damage had already been done; the asbestos-infused insulator had been installed in tens of millions of homes in the United States alone. As over 70% of all vermiculite sold in the U.S. from 1919 to 1990 originated from the Libby mine, it is safe to assume that all vermiculite insulation found in buildings is toxic.

What do I do if I have Vermiculite in my attic?

The State of Wisconsin has a web page dedicated to vermiculite insulation and can be found at https://www.dhs.wisconsin.gov/air/vermiculite.htm Here are some things to consider if you have this type of insulation in your attic:

  • Dispose of waste and debris contaminated with asbestos in tight containers.
  • Do not allow children to play in an attic.
  • Do not launder clothing exposed to vermiculite with family clothing.
  • Do not overreact. According to the National Institute for Occupational Safety and Health (OSHA), asbestos-related illnesses are usually the result of high levels of exposure for long periods of time. Left undisturbed in the attic, asbestos is generally not a life-threatening situation. Furthermore, air generally flows into the attic from the house, and not the other way around.
  • Do not use the attic as a storage area.
  • Hire a professional asbestos contractor before remodeling or renovating if these processes may disturb the vermiculite.
  • Never use compressed air for cleaning around vermiculite. Avoid dry-sweeping, vacuuming, shoveling, or other dry clean-up methods. Wet methods are best.
  • Seal cracks and holes in attics, such as around light fixtures and ceiling fans, where insulation may pass through.
  • Use proper respiratory protection. Disposable respirators or dust masks are not appropriate for avoiding asbestos exposure.

I often find vermiculite insulation under newer insulation such as cellulose or fiberglass batts. It is best to leave the insulation undisturbed, and not use the area for any purpose.

An important note here is that if these materials are left sealed in your walls and are concealed in an unfinished attic the risk is mainly mitigated. If a remodel is planned that will disturb these areas removal by a trained asbestos abatement company may become necessary.

If removal of the Vermiculite becomes necessary, Zonolite (the manufacturer of vermiculite) has a trust fund set up that may help pay for some of the removal costs. There is information and instructions on how to apply for funds at: https://www.zonoliteatticinsulation.com/Hm1.aspx

To summarize, having this type of insulation is not a death sentence for the home, in fact, it might not even need to be removed if certain precautions are performed. It is also vary common in older homes in our service area.

As always, I hope you took some value from this post and if you have any home related questions, please let me know at the email address below.



Aaron M. Zuehlke is the owner and inspector at Zuehlke Inspection Service, LLC, a full-service home inspection company serving Southern Wisconsin. Specializing in Home inspection, Radon Testing, Mold Testing/inspection, Residential Thermal Imaging, and Manufactured Home Foundation Certifications. He also manages several rental properties through Zuehlke Properties, LLC. He can be reached by email at Aaron@Zuehlkeinspections.com or by calling the office at 608-931-7485.

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