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Musings of an Energy Nerd

Fixing Attics With Vermiculite Insulation

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

Almost one million U.S. homes were insulated with vermiculite. Most of this vermiculite contains asbestos fibers which can cause cancer when inhaled.
Image Credit: Environmental Protection Agency

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-value 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 friable asbestos. 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 insulation 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…

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  1. KEVIN ZORSKI | | #1

    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.

  2. GBA Editor
    Martin Holladay | | #2

    Response to Kevin Zorski
    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.

  3. Andy Kosick | | #3

    I'll try to keep this short.
    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.

  4. GBA Editor
    Martin Holladay | | #4

    Response to Andy Kosick
    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.

  5. Paul Baier | | #5

    Vermiculite - test or don't?
    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.

  6. GBA Editor
    Martin Holladay | | #6

    Response to Paul Baier
    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.

  7. Jim Baerg | | #7

    Response to Andy
    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.

  8. Bo Jespersen | | #8

    Possible mitigation from Zonolite Trust
    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.

  9. GBA Editor
    Martin Holladay | | #9

    Response to Bo Jespersen
    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)."

  10. Andy Kosick | | #10

    Response to Bo and Jim
    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.

  11. user-7334393 | | #11

    More background info -

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