Vermiculite Insulation

Vermiculite is a mica-like mineral mined around the world and used in a variety of commercial and consumer products because it is fire-resistant and has good insulation qualities. Studies have shown certain vermiculite insulation products may contain asbestos, which can cause health risks if individuals are exposed to it in the mining, manufacturing, or construction process as well as when asbestos-containing products are improperly handled or disturbed during maintenance, renovation or demolition work.

Vermiculite Insulation
Vermiculite Insulation
Of particular concern is vermiculite ore produced by the Libby Mine in Montana. The Libby Mine supplied the majority of the world market for vermiculite-based insulation products from the 1920s to 1990. After processing, the Libby vermiculite, which has been determined to contain asbestos, was sold as Zonolite® Attic Insulation, and possibly under other brands in the United States and Canada during that time.

While not all of the vermiculite insulation produced by the Libby Mine contained asbestos, and vermiculite from other mines may not contain asbestos, it is not possible to easily determine whether asbestos is present without testing.

To be safe, in the absence of evidence to the contrary, it is best and reasonable to assume that if older vermiculite-based insulation is present in a home, it may contain some asbestos.

Although the amount of asbestos in bulk vermiculite is actually very low, the airborne percentages can increase dramatically if the material is disturbed. Asbestos generally poses health risks only when the fibers are present in the air that people breathe. Like other asbestos products, workers in the mines or manufacturing facilities, and others regularly exposed to asbestos fibers, are the ones most likely to have the greatest potential for serious health effects.

If asbestos fibers are enclosed or tightly bound in a product, for example in cementitious asbestos siding or asbestos floor tiles, there are generally no significant health risks. While, vermiculite is not bound in a cementitious mix, it is generally believed that the risks to the health of occupants of a home are low if the insulation is isolated in an attic, sealed behind wallboards or under floorboards, or otherwise kept from exposure to the interior environment – and otherwise left undisturbed.

Asbestos is most dangerous when it's in a deteriorated condition or other factors are present to cause the fibers to be released into the air. When inhaled in significant quantities, as has been the case with miners and others workers regularly exposed to asbestos, as well as those subject to second-hand exposure, such as family members or those near mines or factories, the fibers can cause asbestos-related disease, which makes breathing difficult, and cancer. Smoking, combined with inhaled asbestos, greatly increases the risk of developing lung cancer.

If and how the exposure to asbestos affects an individual varies, but generally depends on:

  • the concentration of asbestos fibers in the air
  • how long the exposure lasted
  • how often the exposure occurred
  • the size of the asbestos fibers inhaled
  • how long a time has occurred since the initial exposure.

Minimizing the Risk

Vermiculite Insulation in Attic
Vermiculite Insulation in an Attic
The best way to minimize the risk of exposure to asbestos in vermiculite insulation, or any asbestos-containing product, is to avoid contacting or disturbing it in any way.

If vermiculite-based insulation is in a home, the following precautions should be taken:

  • Avoid any activity in attics or other areas containing vermiculite insulation.
  • Do not use the attic for storage if retrieving items from it may disturb the insulation.
  • Make sure anyone entering or working in the attic knows about the possible presence of vermiculite or asbestos and takes the proper precautions.
  • If the attic must be accessed, walk on boards in order to prevent contact and minimize disturbance of the insulation
  • Do not remain in the attic any longer than is necessary.
  • Any gaps around doors or hatches to attics and cracks and holes in walls and ceilings containing vermiculite should be sealed to prevent infiltration to the living area.
  • Use a respirator mask for additional protection. Common dust masks are not effective against asbestos fibers; only respirators listed for asbestos exposure should be used.
  • Do not attempt to remove potential asbestos-containing insulation yourself. Improper removal may do more harm than if left undisturbed.
  • If vermiculite insulation is to be removed, the removal work should be done only by a qualified asbestos removal contractor. Any asbestos-containing material that is removed must be properly contained for disposal at an approved site.

For additional and up-to-date information about vermiculite and other asbestos issues, visit the websites for the U.S. Environmental Protection Agency (; Health Canada (; and/or the Canada Housing and Mortgage Corporation (

This information is provided for general guidance purposes only. Neither HMA Franchise Systems, Inc. nor the local HouseMaster® franchise warrants its accuracy and assumes no liability related to its use. Contact the local franchise office and/or qualified specialists for advice pertinent to your specific house or circumstances. © Copyright DBR 2009. Each HouseMaster franchise is an independently owned and operated business. HouseMaster is a registered trademark of DBR Franchising, LLC.

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