Vermiculite insulation was commonly used to insulate attics from the 1950s to 1970s. Vermiculite is a naturally-occurring mineral found in many parts of the world. It is crystalline and expands into accordion-like, low-density brown strands. The strands are worm-shaped, giving it its name. (Vermiculite has its root in the Latin word for worm.) The vermiculite strands are light, fire retardant and absorbent—good qualities for insulation materials. Interestingly, vermiculite was also used in potting soil where the material’s attributes were also a significant asset.

Potential Hazards of Vermiculite Insulation

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Vermiculite began to be used in many industries in the 1920s. It became a popular insulation material with the construction boom in the 1950s. As insulation material, vermiculite was sold in big bags and applied to the attic floor and down inside exterior walls.

Source of Vermiculite

Most vermiculite was extracted from a mine in Libby, Montana. The mine was rich in vermiculite and also a big deposit of tremolite, a type of asbestos. Unfortunately, tremolite got mixed up with some vermiculite during the process of excavation. The mine shut down and hasn’t been in use for decades.

Problems with Vermiculite

Since some vermiculite had been contaminated with asbestos, it became a highly dangerous material for insulating a house. The asbestos minerals had the tendency to separate into microscopic particles. The particles become airborne and people inhaled them. In some cases, exposure to asbestos lead to life-threatening illnesses, such as mesothelioma and lung cancer. People at the Libby mine were especially prone to these diseases. The hazards of asbestos greatly increase through length and intensity of exposure to the material.


Fortunately, people don’t live in attics. As a general rule, vermiculite insulation should be fine as long as it is left undisturbed behind standing walls or in attics. If your home attic is insulated with vermiculite, the best course of action is to leave it alone so you don’t disturb potential asbestos fibers. Do not go into the attic and do not use the attic as storage. If you are remodeling, get a licensed contractor to remove the vermiculite for you.