What Is Vermiculite Insulation?

Vermiculite is a naturally occurring mineral. It is mined in the US, Russia, China, Africa, and Brazil among other countries. Vermiculite is a good insulation product–but not a great one. It has an R-value of R-2.0 per inch and has been used for over a century to insulate buildings.

Vermiculite Insulation

Why Use Vermiculite as Insulation?

Vermiculite is named after the Latin word meaning “to breed worms.” The insulation is created by heating the mineral which expands up to 30 times its original size by absorbing air. Dead air spaces form the basis of most insulation materials. The heated product looks like worms. It is then crumbled into pellets which can be poured into attics, wall cavities, etc. It is easy to handle and install–making it a good DIY option to use as a top-up or for filling small cavities.

Vermiculite has been used to insulate house attics, walls, and floors since the 1940s. It is still used in some places as building insulation but has been almost totally replaced by products that have better R-values than R-2.0. Many newer products like fiberglass batts and cellulose insulation are also more cost-effective. Insulating an entire house with vermiculite is much more expensive than the alternatives now available. Its lower thermal resistance makes it a less efficient insulator.

Vermiculite is used in other insulation products such as high-temperature insulation, acoustic panels, insulating concrete for floors and roofs, and fireproof wallboard. It is used safely in many other products such as potting soil.

Is Vermiculite Safe?

Yes, vermiculite is very safe to use. It has unique and versatile characteristics. Vermiculite is inert, odorless, lightweight, non-combustible, and highly absorbent. It is mined and manufactured under strict industry protocols. All mines are required to test regularly for asbestos.

There is no evidence that long-term exposure to vermiculite causes chronic toxicity or carcinogens. One mine produced vermiculite contaminated with asbestos–raising questions and fears about the product.

Vermiculite From Libby, Montana

Vermiculite was mined in Libby, Montana from 1919 to 1990 and marketed under the name of Zonolite. It was contaminated with asbestos mined at the same location. Over 70% of all vermiculite sold and installed in North America between 1919 and 1990 came from Libby.

If you have vermiculite in your attic, the safe approach is to assume it contains asbestos. Vermiculite test kits are available from laboratories like LCS Laboratories and EMSL for under $100.00.

Almost no vermiculite from Libby was exported outside North America.

What To Do About Vermiculite Insulation

The Environmental Protection Agency (EPA) lists five guidelines when dealing with vermiculite installed before 1990.

  • The most important is “leave it alone.” Undisturbed asbestos insulation is usually safe.
  • Do not store anything in the attic.
  • Keep children out of the attic.
  • Do not try to remove the vermiculite.
  • If it has to be removed because of renovations or moisture problems, have an asbestos removal contractor do the job. In some locations, it is illegal for homeowners to remove asbestos insulation.