Vermiculite insulation was a popular material in the 1950's and continued with the energy crisis into the late 1970’s. In Canada, it was one of the insulating materials allowed under the Canadian Home Insulation Program from about 1976 to the mid-1980’s.
Vermiculite is resistant to fire and chemical corrosion and is an excellent insulating material.
Pure vermiculite is harmless, but vermiculite mined alongside asbestos can pose a risk for asbestos exposure.
For Canadian use, most of the raw product was from the Libby mine in Montana and was shipped to western Canada. At these plants, it was processed and sold as Zonolite.
According to the U.S. Environmental Protection Agency, 70 percent of the world’s supply of vermiculite came from the asbestos-contaminated mine in Libby, Montana. The Libby mine which became so contaminated by asbestos that the U.S. Environmental Protection Agency (EPA) has now been working to clean the area up for almost 20 years
So what does Health Canada say?
Health Canada released, on April 1st, 2004, the fact sheet It's Your Health - Vermiculite Insulation Containing Asbestos.
Vermiculite is a naturally occurring mineral mined around the world and has been used for insulation and agricultural purposes. However, Health Canada has found some brands of vermiculite insulation may contain tremolite asbestos and could present a health hazard.
These products can cause health risks if disturbed during maintenance, renovation or demolition. However, there is currently no evidence of risk to your health if the insulation is sealed behind wallboards and floorboards, isolated in an attic, or otherwise kept from exposure to the interior environment.
From a distance, vermiculite insulation resembles pebbles or gravel, and it fades to a grey colour over time.
The product is very lightweight because vermiculite has the unique ability to be puffed out when heated, much like popcorn.
Handling or removal of asbestos-containing Zonolite is a task that must be performed by a professional abatement specialist. This can be a significant cost, as they must cordon off the area and place the area under negative pressure to stop the spread of the fibres, and the material must be bagged before it's disposed of. Microscopic asbestos dust cannot be seen, smelled or tasted, and the toxic mineral fibres can slip through a standard dust mask.
The bottom line
The risk of exposure increases with the amount of time spent in the attic, performing renovations or other tasks that will disturb the vermiculite. If you're planning any types of task that will disturb this insulation you should get it tested to see if the vermiculite contains asbestos and if it comes back positive you should seek professional help to remove it prior to any renovations and consider the cost of abatement before you purchase.