Vermiculite Attic Insulation, or What's in Your Attic?

April 01, 2018
Spring 2018
A version of this article appears in the Spring 2018 issue of Home Energy Magazine.
Click here to read more articles about Roof & Attic

Oh, the irony.

Zonolite Attic Insulation (ZAI), was once marketed as a perfectly safe, inexpensive, do-it-yourself attic insulation for home improvement projects. Today, the presence of ZAI represents an expensive professional abatement job for a homeowner, in order for them to move forward with renovation projects or be eligible for generous weatherization subsidies and upfits.

From the 1940s until the late 1980s, millions of homeowners and their contractors unwittingly poured trillions of loose asbestos fibers into their attics in the form of vermiculite mined in Libby, Montana. Zonolite is the brand name of Libby Vermiculite sold by the Zonolite Company and later by W.R. Grace. Although some vermiculite, notably that mined in China and South Africa, is considered to be asbestos free, Zonolite, with approximately 75% of the U.S market, is well known to contain small quantities of hazardous amphibole (a mineral source for asbestos fibers). Thus, while all Zonolite is vermiculite, not all vermiculite is Zonolite. This distinction is of little comfort to homeowners, however, as the adverse economic consequences of vermiculite do not discriminate.

A partially used bag of Zonolite insulation in an attic. (William Ewing)

To Remove or Not to Remove: That Is the Question

The hazards of asbestos to human health are well known. It is also well known that in order for asbestos to be dangerous, it must be inhaled. Fortunately, because vermiculite is typically confined to attics and wall cavities the potential for inhalation would appear to be low. Indeed, EPA advises that vermiculite be left undisturbed. It also advises, however, that if the decision has been made to remove the insulation, it be done by trained professionals, and never attempted by homeowners. The reasoning for these guidelines is illustrated in studies of simulated renovations designed to determine asbestos exposures that a homeowner or contractor might experience during the renovation.

During litigation with W.R. Grace over its liability for Zonolite, counsel for a nationwide class of homeowners commissioned studies designed to evaluate amphibole exposure in homes containing ZAI. One of the studies involved moving aside approximately 14.5 square feet of ZAI with an average depth of 5 inches between the floor joists. The Zonolite was scooped from between the floor joists and into plastic bags, using a standard dustpan. Remaining dust and debris was removed using a whisk broom and dustpan, as an unsuspecting homeowner might. The task took 29 minutes to complete. The results showed the worker exposure to be 4,300 times background asbestos levels (which were extremely low absent disturbance) and the worker’s asbestos exposure to be over 14 times the OSHA excursion limit for a 30-minute period. (OSHA regulations do not apply to work performed in attics by homeowners.) Using additional precautions, such as first misting the vermiculite with water to control dust and using a HEPA vac instead of a whisk broom, resulted in some slight decreases, but still generated significant asbestos fiber release from ZAI. Similarly, asbestos levels in the dust were elevated. A dust sample from the wooden board next to the whole house fan contained 28,000 structures per square centimeter (s/cm2) or 26 million structures per square foot (s/ft2) all Libby amphibole.

fe Cottingham photo 1
Zonolite insulation in an attic around the access hatch. (William Ewing)

But wait, how can this be? As is usually, though not always the case, analysis of the bulk ZAI in the homes used in the study resulted in very low asbestos concentrations of less than 1% and often less than 0.1%. As such, it appears to not even qualify as ACM (Asbestos Containing Material) by EPA definition: “Friable Asbestos Material means any material containing more than 1% asbestos [PLM] that when dry, may be crumbled, pulverized or reduced to powder.”

The answer is found in the fundamental nature of ZAI. Unlike virtually all other asbestos products, which were mixed with gypsum or cement binders and installed either wet (to harden) or in a preformed manner (like pipe insulation), ZAI was never anything more than a loose pile of asbestos-containing rubble! The comparison of vermiculite to other asbestos-containing products is misleading; it’s like comparing apples (wet-applied cementitious products, for example) to oranges (dry-poured, unbound vermiculite). Also significant is the fact that vermiculite is contaminated with amphibole asbestos, whereas the vast majority of asbestos-containing products sold in the United States contain chrysotile asbestos. Once poured into place, the insulation just sat there, but it neither hardened nor chemically reacted to take a set. In short, ZAI has gotten no safer over time. Its hazardous potential remains constant, awaiting only the application of some disturbing force. For this reason, some experts believe that vermiculite should always be treated as if it were ACM, regardless of the level of asbestos. Indeed, the state of New York currently requires loose bulk vermiculite to be designated and treated as ACM notwithstanding the EPA definition.

learn more

The liability of W.R. Grace and the designation of the town of Libby, Montana, as a Superfund site are well documented. See, e.g., Schneider, A., and McCumber, D. An Air That Kills: How the Asbestos Poisoning of Libby, Montana Uncovered a National Scandal. New York: Penguin, 2004; and Schneider, A., and McCumber, D. An Air That Still Kills: How a Montana Town’s Asbestos Tragedy Is Spreading Nationwide. Seattle: Cold Truth, 2016.

See EPA best practices for vermiculite attic insulation.

For more information about the Zonolite Attic Insulation Trust fund and claim requirements, see or

For the EPA definition of ACM, see NESHAPS Regulations 40 CFR 61.141.

Erwin, D. Libby Vermiculite Insulation: A Guide for Homeowners, Homebuyers, Home Inspectors, Real Estate Professionals, Residential Contractors and Tradespersons Edition 1.5 (Jan 1, 2017) Kindle, 2014.

For more on the study mentioned above that was part of the W.R. Grace litigation, see Ewing, William M., et al. “Zonolite Attic Insulation Exposure Studies.” Int. J. Occup. Environ. Health no.16 (2010): 279–90.

Regarding New York regulations, see Shah, M.D., M.P.H, N. R., and Kelly, S. “Testing Requirements for Surfacing Material Containing Vermiculite” (Letter written May 6, 2016 to Interested Party). Retrieved January 16, 2018.

Economic Consequences of Having Vermiculite

Not all vermiculite-related comparisons are without merit. Consider the possibility that the attic contains venomous snakes. They are potentially lethal, but only if they bite you. Similarly, asbestos is only hazardous if inhaled. One solution, therefore, is to simply stay out of your attic and make sure that migration pathways are sealed off. But what if you want to use your attic? What if a prospective buyer wants to use the attic or has an aversion to sharing any portion of his home with snakes? What if, in spite of your efforts to seal off pathways, migration is still possible? What if any number of common residential activities are required, such as installing phone and internet lines, electrical or plumbing repairs, or basic renovations? What if, as long as vermiculite is present, you are considered ineligible for generous weatherization subsidies and energy upgrades offered by various agencies?

More and more, the presence of vermiculite is becoming a sticking point in real estate transactions, and/or the homeowner is deferred and not eligible for various weatherization subsidies, such as free insulation, until the vermiculite is removed. Consider also real-world examples where an ill-advised blower door test was performed, resulting in massive cleanup costs. Or one of several cases where an unwitting contractor knocked a hole in a ceiling or wall to do renovations, only to have vermiculite pour into the living space, necessitating asbestos cleanups costing in the $50,000–100,000 range. Unfortunately, such horror stories are not as rare as one might think.

Decision Time

In a major win for homeowners and those committed to healthy homes, the W.R. Grace litigation resulted in the creation of the Zonolite Attic Insulation Trust fund. Depending on the amount of vermiculite across the country and the number of claims filed over the next 25 years, the Trust will pay between $60 million and $140 million to homeowners who spend money abating vermiculite. To be sure the funds are used as intended, two basic evidentiary requirements must be met—namely, proof that the vermiculite is the Zonolite brand and proof of the claimant’s abatement cost. Also, given the limited amount of funds available and to ensure that the money will be used to assist as many homeowners as possible, the amount of reimbursement is limited to 55% of the abatement costs with a cap of $4,125.

Obviously not everyone can afford to spend a dollar to get back 55 cents, even if doing so abates a potential health hazard and increases the value of their home. Hopefully weatherization agencies and those in a position to offer financial incentives will make vermiculite abatement a priority and channel more resources to vermiculite abatement projects. Such incentives, together with ZAI Trust funds, can help to mitigate the toxic legacy of Libby vermiculite.

Edward B. Cottingham, Jr. was a litigation attorney at the Motley Rice Law Firm, where he worked for 15 years on the property damage team representing plaintiffs in asbestos property damage litigation. He is now in private practice with the Cottingham Law Firm but currently works almost exclusively as the Trustee and Claims Director of the Zonolite Attic Insulation Trust. As Trustee, he is responsible for distributing $60-140 million to an estimated million-plus homeowners in the country with asbestos-containing Zonolite/vermiculite attic insulation. He is also responsible for implementing an education program to alert homeowners and industry professionals to the issues surrounding ZAI/vermiculite.

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