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Vermiculite Insulation | Does It Always Contain Asbestos?

Even if you don’t have asbestos insulation in your home, you may not be safe from the toxic effects of this substance. It turns out that, despite not being made of asbestos, some vermiculite insulation was contaminated by it.

I say “some” because asbestos is not naturally found in vermiculite. Unfortunately, there is no way to visibly tell if vermiculite is contaminated by asbestos. However, there are other ways of figuring it out, which have to do with why vermiculite insulation is so closely associated with the toxic asbestos.

Not all vermiculite insulation contains asbestos. Asbestos in vermiculite insulation is the result of contamination in one mine in America. Unfortunately, over 44 years, this mine supplied 70-80% of vermiculite (under the brand Zonolite). Production ended in 1984, but homes still contain this insulation.

Vermiculite Is Its Own Mineral

Vermiculite is a naturally-occurring mineral that is often described as glossy and flaky. Its colors range from a dark gray to a light brown color. 

This mineral is often found in rocks that contain, or once contained, biotite or phlogopite (types of minerals). Vermiculite is formed when these minerals are hydrothermally altered, i.e., when hot water causes them to alter. 

One of the reasons why vermiculite is ideal for insulation is because, when exposed to high temperatures, it can expand from eight to thirty times its original size. This means that only a bit of vermiculite can create lots of insulation. 

When vermiculite is heated to expansion, it looks a bit like small chunks of wood that have been burnt. The shape of the vermiculite after expansion is often referred to as accordion-like. 

Close-up of vermiculite

Vermiculite is also light and fire-resistant. This is what makes vermiculite ideal material for building products, such as insulation.

Although vermiculite shares certain qualities with asbestos, it is not dangerous on its own.

It also does not inherently contain asbestos. However, vermiculite can become dangerous when it is contaminated with asbestos. 

Asbestos Contaminated One Vermiculite Mine

In a terrible stroke of misfortune, the US-based mine that supplied between 70% and 80% of the vermiculite used in vermiculite insulation happened to be contaminated with asbestos

As I’m sure you know, asbestos is a dangerous substance and a carcinogen that easily finds its way into the air and inside of the lungs, causing damage with exposure to even one single fiber. 

This mine was based in Libby, Montana, and its products were distributed across the US and Canada by a company called Zonolite. 

While the pockets of asbestos were not found everywhere in the mine, the propensity of asbestos to become airborne meant that mining vermiculite spread the dangerous fibers. So, all of the vermiculite mined in the Libby Mines was contaminated or considered to be contaminated with asbestos.

Furthermore, the people in the area surrounding the mines were experiencing adverse health effects related to asbestos exposure because the fibers, once airborne, traveled beyond the borders of the mine.

Zonolite distributed the contaminated vermiculite insulation for 44 years, from 1940-1984, before the asbestos and the danger thereof was discovered.

They ceased insulation production in 1984 and the mine was later closed in 1990.

Can Still Buy Vermiculite Insulation

Despite the Libby vermiculite’s danger to health, vermiculite insulation is not banned because it is not normally an asbestos risk.

Despite this, due to the situation that surrounded the Libby mine, any vermiculite insulation that was produced in the 2000s or later has been tested for asbestos before it is used or sold. 

Zonolite insulation has been off the market for decades with its formal discontinuation being in 1984. 

Despite the fact that only the vermiculite insulation manufactured before 1984 is in danger of containing asbestos from the Libby mines, it is estimated that as many as 35 million homes in the United States still contain this dangerous insulation. 

For this reason, it is imperative that you figure out the type of insulation in your home and the year that it was installed if you live in the US or Canada.

What This Means for Existing Vermiculite Insulation

Homes known to contain vermiculite insulation are not necessarily at risk. You have to determine when the insulation was installed.


Unfortunately, while you can to a certain extent identify asbestos insulation by looking at it, there is no way to visibly detect if your vermiculite is contaminated with asbestos.

If your vermiculite insulation was installed in the 90s or later, your insulation is free of asbestos. 

However, if it was installed in 1984 or earlier, it is very likely that it is Zonolite brand and is, therefore, a hazard to your health. 

If you do not know when your vermiculite insulation was installed, it is best not to assume that it is safe. Instead, it is best to assume that this vermiculite insulation contains asbestos. 

In a situation where your insulation contains asbestos, you may wonder how much there is and how dangerous it is. 

Depending on where the vermiculite that makes up your insulation was mined inside Libby, the asbestos content may vary. This is because the asbestos was not evenly distributed throughout the entire mine.

If it was mined in an area where the asbestos was concentrated, your insulation would have a much greater asbestos content. 

Despite the fact that the asbestos concentrations will vary widely, all insulation materials from the Libby mines should be regarded as dangerous. Asbestos is harmful even in small amounts so the contents won’t matter much. 

You can test your insulation for the presence of asbestos and these companies will also recommend some options to you. However, the most common recommendation is to just leave it alone.

If the asbestos-containing insulation in your home is not at risk of releasing asbestos into the air, professionals can make sure that the insulation is sealed. 

Unfortunately, this sealed insulation can create problems for future renovations and even selling the home since the home value would be impacted by the presence of asbestos, despite it being sealed away. 

The other option, the more invasive one, would be to professionally remove the insulation. This would be more costly and potentially dangerous, but the professionals will be as safe as possible, and the problem will be gone for good. 


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