Vermiculite Insulation: what it is, why you should be concerned, and what you can do about it

Insulation. Fiberglass, mineral wool, cellulose, spray foam… all are extensively used. I’ve even seen wood shavings used as insulation. And then there is vermiculite.

Vermiculite is a naturally occurring mineral that forms from the weathering of micas by ground water. When heated to 800-1100 degrees centigrade it undergoes an accordian-like unfolding and expansion, becoming very light and taking on some insulative qualities. It has an R-value of about 2 per inch, while fiberglass batts have an R-value of about 3.3 per inch. It was mined, processed and used as insulation from the early 1920’s to the early 1990’s, and 70-80% of the vermiculite used as insulation in the United States and Canada was mined from Zonolite mountain in Libby Montana and sold under the trade name ‘Zonolite’.

Vermiculite on its own is harmless, and the mineral mined in Virginia and the Carolina’s, as well as in other parts of the world has been successfully used for a variety of purposes. The vermiculite mined in Libby Montana is another story. Zonolite mountain has become well known for its veins of ‘amphibole’ asbestos, a fibrous silicate mineral. The kind of asbestos found in Libby was not commercially important, but the veins were intermingled with the vermiculite deposits there and the mining buckets scooped up both. Why be concerned? Because we now know that asbestos causes a variety of lung diseases, a fact first highlighted in a series of articles written by Andrew Schneider for the Seattle Post-Intelligencer in November 1999. Libby Montana has become the most expensive superfund cleanup site in the country.

The asbestos in Libby vermiculite is very ‘friable’, meaning it easily crushes and becomes airborne when disturbed. The fibers are microscopic and easily ‘float’ as dust.

W.R. Grace, the last company to mine vermiculite in Libby, filed for bankruptcy and went out of business. The lawsuits have run their course and as of this past June the ZAI (Zonolite Attic Insulation) Trust became operational. The trust will pay 55% of the removal cost and reinsulation up to a total cost of $7500. In other words, they will pay a maximum of $4,125 if the job cost $7500 or more – 55% of $7500 – or if the job costs less… say $5000… they will pay 55% of that cost, or $2,750. This is significant, as it is the first opportunity for financial assistance to an owner of a home who wants to remove vermiculite insulation. The trust will operate for a minimum of 20 years.

W.R. Grace has developed a testing method that can document that vermiculite is or is not Libby vermiculite, and they will reimburse up to $150 for an asbestos abatement firm to gather a representative sample and send it in for testing. It needs to be said that you should not gather your own sample… leave that to the trained and equipped professionals.

Interestingly, the EPA does not recommend testing vermiculite insulation for the presence of asbestos. The reasons are extensive and detailed; suffice it to say that while the presence of asbestos could be confirmed by testing, it cannot be confirmed that asbestos is not present. Therefore, all Libby vermiculite should be treated as ACM (asbestos containing material).

So… what to do if you have a home that has vermiculite, or are considering purchasing a home with vermiculite?

The first and most obvious initial recommendation is to not disturb it. Don’t store things in the attic, don’t let kids play in the attic, don’t let electricians or the cable guy work in the attic, and by all means do not attempt to remove it yourself. Untrained removal could contaminate the entire house and everything in it.

Insulation in an undisturbed attic is isolated and any danger is likely minimal. The EPA says that “If you do not go into your attic, handle, or disturb the insulation, it is likely that you will not be exposed to asbestos fibers from vermiculite insulation.” ( During what became know as the ZAI Science Trial, the court determined that ZAI is indeed contaminated with asbestos, but also determined that, if left alone, vermiculite attic insulation did not represent a substantial health risk to occupants living below it.

If you choose to remove vermiculite, it is a job for a trained asbestos abatement firm. It is not a homeowner job! It is also recommended that an asbestos consultant not affiliated with the abatement firm be involved, both for initial assessment and for final visual confirmation and air testing.

It is a big job, but one made much more manageable now as a result of the ZAI Trust. More information can be found at, and the trust can be reached at:

ZAI Trust

317 Wingo Way

Suite 303

Mt. Pleasant, SC 29464

Toll-free number: (844) ZAI-CALL (844-924-2255)

Fax: (843) 388-3790





A big thank you and credit to Libby Vermiculite Insulation by Daniel Erwin for much of the context and information provided here.

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