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Asbestos in Insulation

From its initial use in the 1860s through to the late 1970s, asbestos was considered a ‘wonder’ material for insulation products because it was tough, fire-resistant, and extremely cost-effective. Unfortunately, companies valued the benefits of asbestos over the health of their customers- many continued to use asbestos in their products for decades after becoming aware of the link between asbestos exposure and diseases like mesothelioma. In fact, asbestos insulation products have been one of the biggest sources of asbestos exposure and asbestos-related disease in the 20th Century.


What is Asbestos Insulation?

Asbestos insulation can be any insulating product that contains asbestos fibers. The concentration of asbestos varies between products with some containing just 15% asbestos and others containing upwards of 85-100% asbestos.
Owing to the versatility of asbestos fibres, the dangerous mineral could be used in a range of different insulation products so its use in residential, commercial, and industrial properties was widespread. In fact, tradespeople working with asbestos insulation were often simply referred to as ‘asbestos handlers’.

Why was Asbestos so Widely Used?

Asbestos is known for its desirable chemical properties- i.e. its fire resistance- but it’s important to understand just how easy asbestos was to work with for manufacturers. As a naturally occurring mineral compound, asbestos is fibrous – with many types having long, curly, and pliable fibres. This made asbestos extremely easy to work into an expansive range of products. It was so widely used, in fact, that asbestos is commonly found in cement, sealants, tiles, and an almost never-ending list of construction products.

Types of Asbestos Insulation

Asbestos insulation products can be grouped into the below four categories:

Loose-fill insulation

One of the most commonly used in residential settings, loose-fill insulation was generally poured or blown on attic floors or the hollow ‘cavity’ inside walls. It was not uncommon for loose-fill insulation to contain 100% asbestos. Loose-fill was particularly dangerous, as even a slight draft can cause the asbestos to become airborne.

Asbestos Insulation Wrappings

Asbestos insulation or wrapping on pipes was widely used in trades such as construction and aboard Navy vessels. Asbestos pipe cladding often looked like corrugated cardboard; using a combination of asbestos and air pockets to insulate the piping. Light and easy to handle, this lagging would wrap around pipes easily and was often itself wrapped with a wool insulation that also contained asbestos. These wrappings often deteriorated over time releasing asbestos fibers when removed from pipework.

Asbestos Block Insulation

Perhaps the simplest use of asbestos insulation was large blocks that were formed to create walls of insulation. Although robust and tightly packed as solid slabs, they created a deadly hazard when cut or damaged.

Spray-on Asbestos Insulation Materials

To reduce the labor required to apply asbestos insulation, spray-on versions were developed. These products were especially dangerous because they became immediately airborne by design and often contained up to 85% asbestos. Although some spray-on insulation products still contain asbestos today, regulations require that they contain no more than 1% asbestos.

Zonoline: Asbestos in Non-asbestos Products

Perhaps the most notorious of all asbestos insulation products is Zonolite – a type of asbestos insulation that was not initially intended to contain asbestos.

Zonolite was the brand name of a vermiculite insulation sold between the 1940s and the 1990s. The vast majority of Zonolite is contaminated with a particular type of asbestos called tremolite. Tremolite is even more dangerous than chrysotile asbestos that was used in many insulation products.

When pure, vermiculite is not dangerous; however, around 75% of the vermiculite that was used in Zonolite was contaminated with asbestos fibres.  As a result, highly toxic asbestos contaminated vermiculite insulation was introduced into millions of American homes.

What Companies are Associated with Asbestos Insulation?

Hundreds of companies were involved in the manufacture of asbestos insulation in the U.S. including:

  • Armstrong Contracting and Supply
  • Certainteed Corporation
  • Celotex
  • Combustion Engineering
  • Crown Cork & Seal
  • E. Thurston & Sons
  • EaglePicher
  • Ehret Magnesia
  • GAF Corporation
  • Johns Manville
  • Kaiser Aluminum
  • Keasbey & Mattison
  • National Gypsum
  • Nicolet
  • Owens Corning
  • Owens-Illinois
  • P. Green Industries
  • Pacor Incorporated
  • Pittsburgh Corning
  • Rock Wool Manufacturing
  • Shook & Fletcher
  • The Flintkote Company
  • Unarco
  • Western MacArthur
  • W.R. Grace

Brand names that asbestos insulation was sold under include:

  • Air Cell
  • Careytamp
  • Celotex
  • Gold Bond
  • Hi-Temp (or Hy-Temp)
  • Hy-Temp
  • Kaylo
  • Limpet
  • Marinite
  • Monokote
  • Superex
  • Supper 66
  • Thermobestos
  • Unibestos
  • Zonolite

What damage does asbestos insulation cause?

The dangers of asbestos a numerous,  and since asbestos insulation products were widely used for decades, these invisible killers have been sitting in millions of homes across the U.S. often undetected.

The health risks of exposure to asbestos insulation can be extremely serious. It has been proved to cause the following diseases:

  • Mesothelioma
  • Lung cancer
  • Esophageal cancer
  • Laryngeal cancer
  • Colon Cancer
  • Asbestosis
  • Pleural plaques and other benign pleural conditions

The invisible asbestos dust that is released from insulation products becomes cumulative when inhaled or swallowed. Asbestos is virtually impossible for the body to break down or expel so it will build up over years causing internal organ damage, inflammation, and genetic damage that often results in cancer.

Who is at risk?

All individuals who come into contact with airborne asbestos fibres are at risk of developing asbestos-related diseases and illnesses.

Workers who manufactured and handled asbestos-containing insulation or other asbestos materials are at the highest risk, as they were often exposed daily without protection. Additionally, any individuals who installed or removed these asbestos products, including construction workers and shipbuilders, were at high risk.  Lastly, family members of those who worked with asbestos insulation are at risk from asbestos fibers brought home on the clothing of those who had worked with it.

Sadly, the issue is not going away any time soon. Today, tradespeople who work in commercial buildings are still often exposed to the dangerous fibers where asbestos insulation materials have been used in the past.