Vermiculite Insulation and IAQ

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Vermiculite Insulation & Asbestos Hazards

Vermiculite is a mica-like mineral that was used as insulation in many houses and commercial buildings (sometimes marketed as “zonolite”) between 1920 and the early 1990s. When heated, it expands like “popcorn” into a loose, lightweight material that is absorbent, fireproof, and a good insulator. Much of this vermiculite contained some asbestos when it was originally mined.

If your house is more than 15 years old and insulated with vermiculite, the insulation may contain asbestos.


You can have a sample of the insulation collected and sent to a laboratory for testing. You should not do this yourself—have the sample collected by a qualified surveyor or consultant, experienced in conducting asbestos hazard assessments. Ask to see his or her qualifications before any samples are collected.


The amount of asbestos in vermiculite is small (typically 1 to 3 percent) and can be difficult to detect. Vermiculite samples must be analyzed using the EPA laboratory method EPA/600/R-04-004, which is specific for vermiculite. A qualified consultant will know which laboratories can accurately test vermiculite samples.


Asbestos in vermiculite insulation is only a health hazard if the vermiculite is disturbed and the asbestos becomes airborne. There is no real risk if the vermiculite is sealed behind walls or isolated in an attic. However, inhalation of asbestos fibres can cause mesothelioma (a fatal cancer of the lining of the lungs or other organs), lung cancer, or asbestosis (a permanent scarring of the lungs that restricts breathing).