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Can You Blow Insulation Over Vermiculite?

Updating or upgrading your insulation is never as simple as simply installing new insulation. This is especially true when you have vermiculite insulation, which has a bit of a checkered history.

Blowing insulation over vermiculite is possible only if a particular condition is met. If this condition is not met, then the practice is considered to be dangerous.

Insulation should not be blown over vermiculite because it may contain asbestos. If installing blown-in insulation is necessary, first test the vermiculite for asbestos. If the test is positive, rather install batt insulation over the vermiculite.

Vermiculite Insulation May Contain Asbestos

Vermiculite is a naturally occurring mineral that is not inherently harmful.

However, between the 1940s and the 1980s, most of the vermiculite used in insulation in North America was supplied by the Libby mine in Montana and distributed by the Zonolite Company. This mine was contaminated with asbestos.

The number of asbestos fibers in vermiculite insulation depends on where the vermiculite was from in the mine and the extent to which that part was contaminated. However, there is no level of safe exposure when it comes to asbestos.

Asbestos is friable, which means it can be easily broken up, and the small fibers are released into the air from where they can be inhaled.


When the particles enter the lungs, they remain there for an extended period. This results in abrasions and accumulated scar tissue in the lungs. The build-up of scar tissue limits respiratory function.

Research also shows that asbestos is a carcinogen that can cause cancer.

Vermiculite Must Be Left Alone

Vermiculite that contains or may contain asbestos is something you should avoid messing with.

The Canada Mortgage and Housing Corporation, Health Canada, the EPA, and other reputable sources recommend leaving vermiculite alone. This means you should not remove it unnecessarily and you should not enter the attic unnecessarily and without taking the proper precautions.

As mentioned, asbestos in your home or building is a hazard for the occupants. However, the risk of removing it is often greater than the risk of leaving it in and ensuring it is not disturbed.

Blowing Insulation Will Disturb the Vermiculite

Blowing in new insulation involves using specialized equipment, i.e., blowers. They are designed to propel insulation into small, hard-to-reach areas.

The blower is connected to a hose pipe, which is attached to an insulation bag. This insulation is then blown into the desired area.

When blown insulation is distributed throughout your attic, it stirs up and disturbs the vermiculite as well as any asbestos fibers present.

Asbestos fibers are light enough to remain suspended in the air for an extended period. In this time, they can move through any small openings into other areas of your home.

Most often, the insulation is blown in from inside the attic. Additionally, because the vermiculite insulation is already laid, reaching certain parts of the attic with the new insulation may require moving the vermiculite to the side temporarily.

This means that the person installing the new insulation will be exposed, the equipment will be contaminated, and the open door access door/hatch can allow any airborne fibers to leave the attic into other parts of the house.

As not disturbing the vermiculite is the recommended practice and blowing in insulation will disturb it, covering it with blown-in insulation is not recommended.

Test for Asbestos if Necessary

There is no way to visibly determine if vermiculite contains asbestos.

If your vermiculite insulation was installed between 1940 and 1990, then the chances are high that it does contain asbestos. Although, it is not guaranteed because there were other mines and suppliers during this time frame.


The only way to tell reliably is to get the insulation professionally tested.

If you really want to add new insulation to the existing vermiculite, you must have it tested for asbestos.

How Does Testing Work?

Testing for asbestos in vermiculite involves sending a sample to an EPA-certified laboratory. LCS laboratory inc., for instance, offers such testing for both public and industrial clients. They also issue guidelines for collecting a sample.

As it’s unsafe to inhale asbestos, remember to put on an N100 or P100 respirator with a NIOSH rating of 95+ percent if you have to sample it yourself. 

However, leaving the job to a certified asbestos abatement specialist is recommended.

When sampling, include samples from a variety of locations and the bottom layer as well. This helps to ensure a more representative sample.

Because the vermiculite is only contaminated with asbestos, it means that there may be places in the vermiculite insulation where there are no asbestos fibers but a few inches away, there may be a whole bunch of these fibers.

In addition, asbestos can settle into the lower layers of vermiculite.

The testing process uses various methods, including microscopic analysis and Chatfield Method. 

Regulation 278 of the Ontario Building Code recommends the latter for analyzing vermiculite insulation following EPA method 600/R-04/004. 

The extraction process of separating the amphibole asbestos fibers makes this method more precise and accurate.

In a two-step extraction process, the sample is soaked and mixed in water, then separated into two fractions. Amphibole materials that are heavier sink while those that are lighter float. This is called the ‘sink fraction’ and ‘float fraction,’ respectively. 

The original sample is weighed along with the fractions to determine the asbestos concentration and the asbestos recovered. The Chatfield Method calculates asbestos percentages by the weight of the sample.

What to Do With the Results

If vermiculite asbestos test results return positive, do not blow in new insulation over it. The risk of releasing the asbestos and being exposed is too high.

You will probably also struggle to find an installer to do the job with a positive asbestos test result.

You should rather contact someone to come and remove it professionally or rather opt for batt insulation over vermiculite.


If the test results show that no asbestos is present, it’s probably okay to blow in new insulation. However, you should not assume that it’s 100% safe to do so.

It is important to remember that asbestos may not be spread throughout the entire vermiculite. Perhaps you or the specialist happen to sample around the asbestos.


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