Vermiculite Insulation (Libby)

Vermiculite insulation became one of the most widespread sources of unintentional asbestos exposure in North America and beyond. Vermiculite is a naturally occurring mineral that expands when heated, producing lightweight, fire-resistant granules ideal for insulation. However, the world's largest vermiculite mine, located near Libby, Montana and operated by the W.R. Grace company under the brand name Zonolite, was contaminated with naturally occurring tremolite and winchite asbestos.

From the 1920s through 1990, an estimated 35 million homes in the United States alone received Zonolite vermiculite attic insulation. The product was sold as a loose-fill, pour-in-place attic insulation that homeowners could install themselves. It was also used as an aggregate in lightweight concrete, plaster, and fireproofing sprays. Approximately 70 % of all vermiculite sold in the US originated from the Libby mine.

The contamination was catastrophic for the town of Libby. Over 400 residents have died from asbestos-related diseases, and the EPA designated Libby as a Superfund site in 2002. W.R. Grace filed for bankruptcy in 2001 due to asbestos liabilities and established the Zonolite Attic Insulation Trust (ZAI Trust) to help fund remediation for affected homeowners.

Vermiculite insulation appears as small, accordion-like granules, typically grey-brown, silver-gold, or tan in colour. It is found poured between attic joists, within wall cavities, and sometimes mixed into concrete or plaster. While not all vermiculite contains asbestos, the EPA recommends treating all vermiculite insulation as if it is contaminated unless testing proves otherwise.

Disturbing vermiculite insulation by walking on it, blowing additional insulation over it, or performing attic renovations can release tremolite asbestos fibres. The material should not be removed by homeowners. Professional testing and, if necessary, professional removal or encapsulation by qualified contractors is essential. The ZAI Trust may cover a portion of abatement costs for eligible properties in the United States.