Fixing Attics With Vermiculite Insulation

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Fixing Attics With Vermiculite Insulation

In an older house, 8 inches of attic insulation is sometimes much, much worse than no insulation at all

Posted on Apr 17 2015 by Martin Holladay

If you're under the impression that natural insulation materials are the safest ones to use, it might be time to think again. Vermiculite is a natural insulation material — but it’s one that you definitely don’t want to have in your attic.

Vermiculite is a mineral mined from the earth, composed of shiny flakes that look like mica. When this mineral is put in an oven, it expands like popcorn. Expanded vermiculite is lightweight, fire-resistant, and odorless; since it has an R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of about R-2 per inch, it was used for decades as an insulation material.

There is only one problem with this wonderful material: most vermiculite contains friableEasily broken down. A friable insulation material may lose its effectiveness; some friable materials release hazardous dust into the home. asbestosMineral fiber once commonly used in many building materials, including insulation, fireproof siding, and resilient flooring. Inhalation of invisible asbestos fibers can lead to chest and abdominal cancers as well as scarring of the lungs. The use of asbestos in some products has been banned by the EPA and the U.S. Consumer Products Safety Commission; manufacturers also have adopted voluntary limitations on its use. When found in older buildings (most commonly in floor tiles, pipe and furnace insulation, or asbestos shingles), the product's friability is a major determinant in how it must be handled during renovations. More information: When inhaled, vermiculite dust can cause cancer.

Owners of homes with vermiculite have a huge headache. If your attic contains vermiculite:

  • It’s dangerous to enter your attic.
  • It’s dangerous to perform a blower door test.
  • It’s dangerous to perform any attic air sealing work until all of the vermiculite has been removed by a certified asbestos abatement contractor, at a cost ranging from $7,000 to $12,000.
  • It’s dangerous to install cellulose insulationThermal insulation made from recycled newspaper or other wastepaper; often treated with borates for fire and insect protection. on top of the vermiculite.

That’s why it’s so much better to have an attic with no insulation at all than it is to have an attic with 8 inches of vermiculite.

If an attic is insulated with a thin layer of vermiculite — a layer that provides less than the minimum R-value required by code — it's hard to come up with a good way to improve the insulation layer, especially if the ceiling has air leaks. Addressing attics with vermiculite is a particular challenge for weatherization agencies.

Where does it come from?

Vermiculite insulation was sold in the U.S. from 1919 to 1990. More than 70% of U.S. vermiculite came from a single mine near Libby, Montana. Vermiculite insulation was sold in bags to builders and homeowners under the Zonolite brand name. Founded in 1919, the Zonolite company was acquired by W.R. Grace Company in 1963.

According to a 1985 estimate made by the Environmental Protection Agency (EPA), about 940,000 American homes were insulated with Zonolite.

Zonolite was rarely installed after the mid-1980s. Closed in 1990, the Libby mine became an EPA Superfund site in 2002.

Vermiculite from the Libby mine contained asbestos fibers (variously described as amphibole, tremolite, or actinolite asbestos). Although not every bag of Zonolite contained asbestos, a lot of them did — enough that all vermiculite-insulated attics in the U.S. must be assumed to contain asbestos.

Health risks

Breathing vermiculite dust is definitely dangerous. Vermiculite dust often contains asbestos fibers, and inhaling asbestos fibers can cause asbestosis, lung cancer, or mesothelioma. The latency period for asbestos-related cancers is 15 to 45 years.

Encapsulated vermiculite (for example, vermiculite installed in stud cavities) is not particularly dangerous, as long as no one opens up the wall or engages in demolition. Disturbing vermiculite insulation on an attic floor is definitely dangerous.

According to the EPA, “Exposure to asbestos increases your risk of developing lung diseases … The risk of disease increases as the level, duration, and frequency of exposure increases. That risk is made worse by smoking. If you are concerned about possible exposure, talk to your doctor.”

What does vermiculite look like?

Have you poked your head into your attic and looked at the insulation, wondering if it is vermiculite? The key to the identification process is looking at your insulation without touching it. Whatever you do, don’t disturb it or move it around — and don’t spend any more time in the attic than necessary.

Vermiculite is a pour-in-place insulation made up of small particles (not fibers). The particles vary in size from rice-sized grains to particles that are almost an inch long.

The particles are often (but not always) shiny, and sometimes look like very small pebbles. The color of vermiculite insulation ranges from gray-brown to silver-gold.

Should I test the stuff in my attic?

In the past, some government agencies recommended that vermiculite insulation should be tested for asbestos. However, these days all reputable sources recommend that homeowners should assume that all vermiculite insulation contains asbestos, and that homeowners and builders shouldn’t waste any money on testing.

According to the EPA, “Since the Libby mine was estimated to be the source of over 70 percent of all vermiculite sold in the United States from 1919 to 1990 and vermiculite from Libby was contaminated with asbestos, further testing is not necessary to take the appropriate precautions. … While you can hire a trained professional to test your attic for asbestos, this may be expensive and, depending on the methods used, might give you erroneous results.”

According to the Vermont Department of Health, “Due to the uncertainties with existing testing techniques, it is best to assume that the material may contain asbestos.”

Testing vermiculite for asbestos is no longer recommended because:

  • Commonly used testing procedures are unreliable, and
  • A vermiculite sample gathered near an attic access hatch may not be representative of vermiculite installed elsewhere in the attic. Even if the bag of Zonolite installed near the attic hatch was asbestos-free, other bags of Zonolite used to insulate the rest of the attic might have contained dangerous levels of asbestos.

Marc Companion, a civil engineer working for Vermont’s Healthy Homes Program, sums up current advice: “Don’t bother to pay money to test for asbestos. Presume that the vermiculite contains asbestos.”

Advice to owners of homes with vermiculite in the attic

If your house has vermiculite in the attic:

  • Don’t touch or disturb the insulation in your attic.
  • Don’t use your attic for storage.
  • If at all possible, don’t enter your attic.
  • Don’t allow children to play in the attic.
  • Don’t open your walls to see if there is vermiculite inside.
  • Don’t attempt to remove the vermiculite yourself. If you want to have the vermiculite removed, hire a certified asbestos abatement contractor for the job.
  • Don’t let untrained contractors — for example, electricians or cable installers — into your attic, since contractors may cause a new hazard where none existed.
  • Install a warning sign near your attic access hatch reading, “Cancer Hazard: Insulation contains asbestos. Do not disturb or create dust.”
  • Remember, common dust masks are not effective against asbestos fibers.
  • It’s probably a good idea to seal any cracks in your ceiling (for example, cracks around ceiling-mounted electrical boxes) to reduce the chance that vermiculite dust will enter your home. This work should only be performed from below — never from the attic.

Is it safe to do a blower-door test in a house with vermiculite?

At this year’s Better Buildings By Design conference in Burlington, Vermont, Marc Companion was asked about the advisability of blower-door tests on homes with vermiculite insulation. He answered, “It’s a can of worms. Frankly, it’s an issue that we have not yet addressed in Vermont. Our advice is, ‘Don’t do a blower door test.’”


Vermiculite has many uses. In addition to being used for insulation, it is often used in potting soil mixes and as a soil amendment. If you have a greenhouse or do a lot of gardening, you may be wondering whether your health has been damaged by handling vermiculite.

Unfortunately, there is no clear answer to the question. According to Health Canada, a government agency, “Based on current information, there is no evidence that vermiculite currently available for horticultural purposes (e.g. potting plants) is a health risk when used as directed.”

However, information provided by the EPA is more nuanced. The following question is posted on a Q&A site maintained by the EPA: “I used vermiculite to enhance my potting soil. Should I be concerned?”

Here’s the response: “EPA’s investigation into these products indicates that consumers face only a minimal health risk from using vermiculite products at home or in their gardens. To further reduce the risk associated with the occasional use of vermiculite products during gardening activities, EPA recommends that consumers use vermiculite outdoors or in a well-ventilated area; avoid creating dust by keeping vermiculite damp during use; and avoid bringing dust into the home on clothing.”

Companion continued, “Some people wonder, ‘Maybe we could do a pressurized blower door test?’ I don’t recommend it. It’s probably not safe to do it. A blower door and asbestos don’t go well together.”

A pilot project in Vermont

Accompanied by co-presenter Todd Hobson (who works at Clay Point Associates, a consulting firm specializing in hazardous materials), Marc Companion gave a presentation at the Burlington conference called “Weatherization and Vermiculite: Toward Solutions.”

Companion began the presentation by describing the extent of the vermiculite problem. “In Vermont, 20,000 houses have vermiculite,” said Companion. When these homes need energy upgrades, “Weatherization work is often halted until vermiculite is removed. Certified removal is expensive.”

Companion continued, “We want to seal air leaks in the attic deck, and we can’t seal it if there is vermiculite. You need a certified contractor, and there are insurance and liability issues. To remove vermiculite from a typical Vermont attic costs $7,000 to $12,000. Low-income weatherization agencies often just walk away. There are now 406 families on Vermont’s weatherization waiting list because of vermiculite.”

Hobson chimed in. “When owners investigate the cost of removal, they find out it is unaffordable,” he said. Hobson went on to describe the required steps for certified vermiculite removal, which include the need for polyethylene containment barriers, the creation of a negative pressure work environment, the installation of HEPA filtration equipment, and wet removal methods that require sprayers and misters. Workers need respiratory protection as well as protective clothing and gloves.

Brainstorming for a new approach

In light of the high cost of certified asbestos abatement, a group of concerned Vermont experts — including both weatherization experts and asbestos experts — decided in March 2013 to form a brainstorming group to try to develop lower-cost approaches to the vermiculite problem. Companion asked, “Do we really need to remove the vermiculite? Not really. We really just need access to the attic floor.”

The group came up with a new approach to handling vermiculite — one they dubbed the “hybrid approach.” Companion explained, “The key aspect of the hybrid approach is to put weatherization and asbestos abatement personnel together in the attic. The asbestos people will pull aside some of the vermiculite as directed by the weatherization supervisor. Then weatherization work [air sealing] happens. The abatement contractor does the spray foam air sealing. Then loose-fill cellulose is installed on top of the vermiculite.”

The Vermont working group obtained funding for a pilot project to perform “hybrid approach” weatherization work at five Vermont houses insulated with vermiculite.

Of course, since the hybrid approach requires workers to disturb vermiculite, it is still essential to follow all of the safe work practices required for an asbestos abatement job. According to Hobson, “You need a clean room, a shower, a dirty room, and containment of the abatement work area. You need a makeup air source.”

The hybrid approach costs less than full abatement

The results of the pilot project were mixed. The good news is that tests revealed that this type of work can be performed without endangering occupant health. According to the results of air sampling, no vermiculite-related asbestos was detected in the living area directly below the attics during or after the weatherization work.

Although the cost of the work was substantial, it was less than a full asbestos abatement job. “The hybrid approach cost $3,400 to $5,018 per house,” Companion reported, “That’s 45% to 65% less than full abatement. Some savings come from the fact that weatherization work and asbestos work happen at the same time. We also saved the cost of disposing of the vermiculite.”

Companion provided a “lessons learned” list. “This approach is not for every situation,” he reported. “It makes more sense for large attics than smaller attics. We learned that you can’t easily remove vermiculite from the slopes. We also learned that abatement contractor skills are critical. For this approach to work, the asbestos contractors need weatherization training.”

Companion also noted, “One possible criticism of this approach is that we now have more contaminated material than before.”

After attending the presentation by Marc Companion and Todd Hobson, I came away with two thoughts:

  • The problem of vermiculite insulation is a thorny one.
  • While no simple solutions to the vermiculite problem have yet emerged, I’m glad that weatherization workers and abatement contractors are wrestling with the problem and experimenting with new approaches.

During the discussion that followed the presentation, an audience member suggested that the best solution might be to install rigid foam on the interior side of the ceiling, followed by new gypsum drywall. This sounds like a sensible way to beef up the R-value of a vermiculite-insulated attic — as long as the ceilings aren’t too low.

Postscript: In response to litigation initiated by owners of homes with Zonolite insulation, the W.R. Grace Company agreed to set up a fund called the Zonolite Attic Insulation Trust. According to the trust's web site, "The Trust may provide a reimbursement contribution of 55% of the abatement cost for eligible Claimants up to a ceiling of 55% of a $7,500 removal bill (or $4,125). For example, if you spent $7,500 removing and replacing the insulation, you are potentially eligible for the maximum reimbursement of $4,125. If you spent $3,000 for abatement and re-insulation, you are potentially eligible for reimbursement of $1,650 (55% of $3,000)." Visit the trust's web site for more information.

Martin Holladay’s previous blog: “Using a Glycol Ground Loop to Condition Ventilation Air.”

Click here to follow Martin Holladay on Twitter.

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Image Credits:

  1. Environmental Protection Agency

Apr 17, 2015 2:00 PM ET


Martin - Thanks for the informative article. Air sealing from below seems like a good idea with added cellulose on top. Why would extra foam be needed before the new drywall? Or to ask it another way, after sealing all the penetrations into the attic, what would the foam be doing that the new drywall layer was not doing? It seems akin to a double stud,cellulose filled wall vs. a stud wall with foam sheathing, but in this case there is pretty much unencumbered drying to the attic side.

Apr 17, 2015 2:07 PM ET

Response to Kevin Zorski
by Martin Holladay

The suggestion to install rigid foam on the interior side of the ceiling drywall (or plaster) is not an air sealing measure. It is an attempt to increase the R-value of a ceiling with a thin insulation layer.

There is no easy way to add cellulose on top of vermiculite, as you suggest. Any attempt to do that requires the help of an asbestos abatement contractor, which costs thousands of dollars above and beyond the cost of the cellulose insulation.

Apr 21, 2015 2:11 PM ET

I'll try to keep this short.
by Andy Kosick

Thanks for this post because the most dangerous aspect of vermiculite is that almost nobody knows about it.

This stuff is all over my area, in my own attic, and the bane of my existence as a home performance contractor. Once I became aware of the problem (after working in my own attic) I've become an advocate for a real solution and am extremely frustrated by the giant "gray area" that is vermiculite, I feel it is often willfully ignored. If you bring up this subject to an official (code, MiOSHA, EPA, even abatement contractors) they're eyes all get the same look fear and embarrassment (I know this because I've felt this way myself now), fear because they know it's a serious issue and they don't have a good answer for you, embarrassment because they're going to give it to you anyway. The answer is of course don't touch it or have it abated, and everybody knows that neither of those things are going to happen. I've done energy audits on half a dozen houses now that the owners had just purchased and I was the first person to tell them about the vermiculite in the attic. I've also never had a single home owner have it abated and the reason every time is cost. Usually they just hire someone else to blow over it. There's probably a electrician or insulator within a few miles of me being exposed to it as I type this. You get the point, so enough of me complaining.

Solutions. While I applaud any attempt at a solution I have to say I disagree with the "hybrid method" above. It's basically kicking the can, I have a feeling it's still more expensive than most home owners are willing to pay for and in the end the attic is still full of asbestos. I would liken it to adding 4 inches of cellulose to an attic (big pet peeve of mine), the truck's in the driveway, the hose is in the attic, but save a little money and only add 4 inches. As I see it if you have to touch it at all and get in a HAZMAT suit to do so, get it out of there so someone else doesn't have to deal with it again someday. The real problem is how do we pay for it. It's expensive to do abatement, the abatement contractor I deal with most around here says that by far the easiest way to abate it is with a large HEPA vac setup and the only way to get the cost of that down is to do more of it. Using that method and coordinating with the abatement contractor in terms of them removing and us air sealing and insulating, they've got their cost down to $4000 to $5000 on some smaller attics (800-1000sqft). This is full abatement and seems on par with the hybrid pilot. Of course that's a smaller attic and I've never actually got to do one of these only price them out.

The only solution I have to suggest is to force the issue and finance it. Spinning off of my experience above, since this stuff is friable, why can't disclosure of vermiculite be required at time of sale, with a mechanism to include all or most of the cost of abatement in the mortgage. Most people are honestly concerned about this when informed and if the cost was mixed into a mortgage, which has way bigger numbers in it than the cost of abatement, and the resulting air sealing and insulating offsets that cost a bit, I think people would bite and we would finally start getting rid of some of this stuff. Does anyone think this is a good idea? It's almost like an EEM except there's going to be some cost that the energy savings won't cover in the life of the mortgage. Maybe some kind mortgage insurance would have to cover it. I'm just throwing stuff out here, this is the best I've got and would appreciate any advice on how to get the ball rolling.

Apr 21, 2015 2:25 PM ET

Response to Andy Kosick
by Martin Holladay

Thanks for your comments. I agree with you. I think that a careful reading of my article will reveal that I have the same misgivings about the "hybrid approach" that you do. (In fact, the researchers who were part of the pilot project share most of the same misgivings.)

The fact is, there is no easy solution to this problem. Your suggestion that the presence of vermiculite be disclosed during a home sale so that the cost of abatement can be rolled into a mortgage is a good one.

Apr 22, 2015 11:13 AM ET

Vermiculite - test or don't?
by Paul Baier

I question the comment about not having the vermiculite tested. We recently bought a house that had an inspection revealing "vermiculite". In Canada - my understanding is - 50-60% of the vermiculite is sourced from the Libby mine - the rest came from Canada (no asbestos). We worked in the abatement cost into the buying price. We plan to tear down the house and build a new one now - so asbestos contamination was a huge concern. Our environmental assessor was confident that it was NOT vermiculate despite "looking like it" What our environmental lab assessment found was Mica Flakes insulation. There is NO asbestos in this - and in fact it is still sold. We saved 15k in abatement and have moved on to other concerns. Assuming every "vermiculite" looking insulation is deadly will ultimately cost consumers greatly.

Apr 22, 2015 11:43 AM ET

Response to Paul Baier
by Martin Holladay

I appreciate your comments. Certainly in the U.S., the issue of "Should we test or not?" has been batted around a lot over the last 15 years or so. I am accurately reporting the current consensus from vermiculite experts: basically, it's "Don't bother to test."

This advice stems from the fact that a lot of testing results were false negatives. You are warning us of a different problem -- the possibility that visual inspection (rather than testing) could result in false positives.

It's hard to evaluate your warning without knowing more about the insulation material you describe as "mica flakes insulation." I have no idea (a) whether this material was only sold in Canada, or was also sold and installed in the U.S., or (b) whether mica flakes look anything like vermiculite -- in other words, whether it takes a trained eye to distinguish between these two types of insulation, or whether a few photos could clarify the issue.

Apr 22, 2015 11:47 AM ET

Response to Andy
by Jim Baerg

Here in Montana, where there is lots of Zonolite in attics, the Weatherization crews routinely test for aesbestos. Cost is about $45 as I recall. An inspector suits up, carefully takes 3 samples from different parts of the attic, mixes them into one and sends the sample in. Turn around is very quick. If the insulation is clean, then work can proceed. It happens enough to make the testing worthwhile.

Regarding home sales; I agree that this is the obvious point of intervention, especially financially. Many Real Estate agents don't want to know what is in the attic because it really complicates the sale. If they have found unsafe conditions, they have to disclose it to the potential buyer. Sounds like we need to get some education and collaboration between the Realtors and the abatement people so the Realtors can guide their clients. $5,000 on a 30 year note at todays rates is about $30/month.

Apr 22, 2015 2:42 PM ET

Possible mitigation from Zonolite Trust
by bo jespersen

Another great article. Thanks.

A good friend, Richard Burbank, sent me this link; ( I have not had any experience with the trust yet but plan on contacting them the next time we run into the product.

Apr 22, 2015 3:05 PM ET

Response to Bo Jespersen
by Martin Holladay

Thanks for the information and link about the Zonolite Attic Insulation Trust. Much appreciated.

The Web page notes, "The Trust may provide a reimbursement contribution of 55% of the abatement cost for eligible Claimants up to a ceiling of 55% of a $7,500 removal bill (or $4,125). For example, if you spent $7,500 removing and replacing the insulation, you are potentially eligible for the maximum reimbursement of $4,125. If you spent $3,000 for abatement and re-insulation, you are potentially eligible for reimbursement of $1,650 (55% of $3,000)."

Apr 22, 2015 4:23 PM ET

Response to Bo and Jim
by Andy Kosick

Thanks for the link to the Zonolite trust.

It looks as though it may be a bit of a gable. Some form of product identification is necessary by receipt of purchase, bag photographed in attic, lab results, or a sample sent to them. I've never seen a receipt, the only bag I've seen is from my own attic, and lab results have had a lot of false negatives. That's the reason testing not recommended. As I understand it asbestos content varied from bag to bag so the 3 places you sample could be negative but 3 feet away could be positive. Also, as I understand it, the lab test is threshold based, the results from one I had done showed a small amount of asbestos content but it was below a threshold so it's considered negative. So, on one hand this makes me nervous about working with any vermiculite regardless of test results and on the other means there's a definite chance of not qualifying for a claim. The final option of sending them a sample states that it "does not test for asbestos content", so they must be identifying it by other means. In all cases the work has to be done first making the claim seem like a bit of a gable.

That said, I'll definitely pursue this on the next job, in fact I might contact a previous customer.

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