Written By: Michelle Whitmer,
Last modified: April 13, 2021
Quick Facts
  • Years Produced:
    1866 – 1978
  • Places Used:
    Attics, ceilings, walls and basements in residential and commercial construction as well as around pipes, boilers, furnaces and electrical boxes
  • Toxicity:
    High
  • Asbestos Use Banned:
    No
  • Friable:
    Yes

What Is Asbestos Insulation?

Pipe near rafters with damaged asbestos insulation
Damaged asbestos insulation around pipes in basements presents an exposure risk.

Asbestos insulation was the biggest source of asbestos exposure for workers throughout the 20th century, and it remains a toxic hazard in many homes and businesses to this day. Asbestos was long considered an ideal material for almost all types of insulation, until its cancer-causing effects were revealed to the public.

The naturally occurring mineral has a unique fibrous nature that allows it to take on a cotton-like consistency. The space between the fibers slows down the transfer of heat through the material to make it extremely resistant to heat.

Asbestos fibers are easily pulled apart, which allows manufacturers to mix it with other materials such as magnesia to make different types of insulation. If insulation was needed, asbestos was used. For much of the 20th century, insulators were often referred to as “asbestos workers” because they handled the material so frequently.

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Companies Associated with Asbestos Insulation

Some brands of asbestos-containing insulation include:
Manufacturer Brand
Johns Manville Air Cell, Marinite, Superex, Thermobestos
Armstrong Contracting and Supply Hi-Temp, Kaylo, Limpet
W.R. Grace Zonolite, Monokote
National Gypsum Gold Bond
EaglePicher Super 66
Pittsburgh Corning Unibestos
Celotex Careytemp
Nicolet Hy-Temp

Asbestos insulation manufacturers in the U.S. included:

  • 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

Types of Asbestos Insulation

Asbestos-containing thermal insulation can be grouped into four major categories: Loose-fill, wrap, block and spray-on.

Loose-Fill Asbestos Insulation

Loose-fill asbestos insulation

Loose-fill insulation is designed to be poured onto attic floors or blown into hollow spaces inside walls and other building structures. Fluffy loose-fill asbestos insulation — sometimes made almost entirely of the toxic mineral — is extremely dangerous because even a slight air current can disturb it, sending inhalable asbestos fibers into the air. This product was also known as asbestos attic insulation.

Asbestos Insulation Wrappings

Insulation coverings for pipes, ducts and other plumbing and HVAC components in old buildings often contain asbestos. Asbestos pipe insulation was also a major health hazard on Navy ships for many decades.

Asbestos pipe wrapping

Before 1980, insulators typically wrapped pipes with asbestos-based air-cell insulation, which is essentially a type of cardboard made out of asbestos paper. This kind of insulation becomes crumbly as it ages, releasing large quantities of asbestos dust if it is damaged or cut off to be replaced. A product known as asbestos wool insulation was also wrapped around pipes.

The fabric of old valve insulation jackets also often contains asbestos fibers, which may be dispersed through wear and tear.

Asbestos blocks

Asbestos Block Insulation

One simple way to insulate the wall of a building is to glue a slab of insulation to it. In the past, these insulation blocks or boards were often made of nearly pure asbestos, which creates a major exposure hazard whenever such blocks are sawed or damaged. This product was also known as asbestos wall insulation.

Spray-On Asbestos Insulation

Spray-on asbestos

Spray-on insulation was developed to reduce the amount of labor required to apply insulation and fireproofing materials to ceilings, walls and structural beams. You can see spray-on insulation in many large commercial buildings where the ceiling is coated with a thick layer of grey material.

Unfortunately, many spray-on insulation products contained up to 85% asbestos, putting the workers who applied them at extreme risk. Further, these products can be damaged easily, releasing a cloud of asbestos fibers into the air. They present a major exposure hazard unless they are thoroughly encapsulated.

Since 1990, spray-on insulation products containing more than 1% asbestos have been prohibited in the U.S. unless the products are encapsulated with a bituminous or resinous binder during spraying.

Other types of asbestos-containing insulation include:

  • Cement
  • Plaster
  • Certain brands of batt insulation
  • Electrical panels

Zonolite and Mr. Fluffy Insulation

Zonolite insulation in an attic
Zonolite attic insulation was installed by many homeowners until 1984.

One of the most notorious asbestos insulation products is Zonolite insulation. It originated in the 1940s, and production thrived beginning in the 1960s when W.R. Grace and Company acquired the brand. Zonolite is a type of loose-fill insulation made of asbestos-contaminated vermiculite, and it was installed as attic insulation in millions of American homes.

Unlike many other insulation products of the time, Zonolite was never actually intended to contain asbestos. The vermiculite used in the product came from a mine in Libby, Montana, which was contaminated with asbestos. Zonolite contains tremolite asbestos, which is a type of asbestos known to cause disease at lower rates of exposure than other types of asbestos.

An estimated 30 million homes may still have Zonolite in their attics, according to internal documents from the U.S. Environmental Protection Agency and the Agency for Toxic Substances and Disease Registry.

Asbestosfluf insulation vintage ad
Also known as Mr. Fluffy, Asbestosfluf was widely used throughout Australia.

One of the most toxic insulation products used in Australia was the Asbestosfluf attic insulation sold in the 1960s and 1970s by a company popularly known as “Mr. Fluffy.” The lighthearted name comes from the fluffy appearance of the loose-fill insulation product.

The Australian government carried out a removal program in the 1980s but did not appreciate the true extent of the contamination. Even though the Asbestosfluf insulation was successfully removed from the attics where it had been installed, by that time mineral fibers had already been blown into every nook and cranny of the affected homes.

After conducting new tests in 2014, Australian government officials had to inform residents of the so-called “Mr. Fluffy homes” that their homes were still heavily contaminated. Because removing the asbestos in the homes poses such a challenge, the government has actually found it less costly to buy the homes outright and demolish them.

Diseases Asbestos Insulation Can Cause

Asbestos-related illnesses, such as asbestosis and mesothelioma, develop when microscopic asbestos fibers accumulate in the body after being inhaled or swallowed. Asbestos is almost impossible for the body to break down or expel, and over many years the toxic mineral fibers cause scarring, inflammation and genetic damage to cells.

Asbestos insulation is known to cause the following diseases:

  • Mesothelioma
  • Lung cancer
  • Ovarian cancer
  • Laryngeal cancer
  • Asbestosis
  • Pleural plaques and other benign pleural conditions

For much of the 20th century, it was common for the asbestos content of most insulation products to be 15% or greater, with many products being almost entirely composed of friable asbestos, which can easily release dust into the air. Historically, most asbestos-related diseases have been caused by occupational exposure. The greatest risk by far is borne by those who worked in the factories that manufactured asbestos insulation products.

In addition, whenever construction workers and shipbuilders poured or blew in loose-fill asbestos, handled crumbling asbestos pipe wrapping, cut asbestos blocks to size or sprayed asbestos insulation onto a structure, enough asbestos dust was released to endanger the health of everyone in the surrounding area. Asbestos insulation remains in so many buildings in the U.S. that tradesmen are still routinely at risk of exposure.

Occupations at risk of coming into contact with asbestos insulation include:

Families living in old homes and employees working in old commercial buildings are also endangered when aging asbestos insulation is disturbed through maintenance, renovation or wear and tear. Asbestos insulation in old school buildings has created an ongoing public health crisis that has affected multiple generations of students and teachers. Today, asbestos-related illnesses disproportionately affect veterans because of the military’s extensive use of the toxic mineral in the past.

Many experts also warn that the rise of do-it-yourself renovations may lead to a new wave of asbestos victims if homeowners do not take the proper precautions when fixing up old homes.

If you develop an asbestos-related disease it is important to seek medical care from a doctor specializing in your diagnosis. These doctors work at the nation’s top cancer centers where you gain access to innovative treatment and clinical trials.

Compensation for Exposure to Asbestos Insulation

Because manufacturers continued to incorporate asbestos into their insulation products even after experts reported on its toxicity, victims of asbestos-related diseases have won thousands of lawsuits against these companies. Many of them, including W.R. Grace and Johns Manville, were caught hiding what they knew about asbestos from employees and government officials.

  • In September 2020, a California jury awarded $2.5 million to a retired U.S. Navy admiral who claimed he developed mesothelioma by working with asbestos insulation made by Metalclad Insulation Corp. during his service.
  • In May 2009, a jury awarded $6 million to Dean Busatto and his wife after he was diagnosed with mesothelioma. Busatto had been a machinist mate in the U.S. Navy from 1956 to 1959, where he worked with asbestos-containing insulation jackets made by Melrath Gasket Inc.
  • In 1996, a verdict of nearly $3.5 million was awarded to the estate of Jesse Rivera, who died from mesothelioma cancer. Rivera worked for Owens Corning from 1963 to 1966, and was exposed to asbestos in its Kaylo insulation product.

Since the 1980s, many asbestos product manufacturers have filed for bankruptcy because of the volume of lawsuits against them. Johns Manville set an important precedent by filing for bankruptcy in 1982 and resolving it six years later by setting up the $2.5 billion Manville Personal Injury Settlement Trust, which provides compensation to present and future claimants. This plan was considered a novel use of bankruptcy law at the time, but many other companies have set up similar trust funds since then.

An experienced mesothelioma attorney can review your case and advise whether you qualify to file trust fund claims and lawsuits, such as a personal injury claim or wrongful death claim.

How to Handle and Dispose of Asbestos Insulation

Do-it-yourselfers should never attempt to abate asbestos insulation. It is important to hire a licensed asbestos abatement company to remove asbestos insulation because these materials are highly friable and handling them will result in asbestos exposure.

Make sure the company you hire is licensed to perform asbestos abatement. You could incur steep fines for improper asbestos removal and disposal if you don’t select a licensed company to do the job properly and safely.

The long latency period of asbestos-related diseases allowed the mass use of asbestos insulation to continue up until successful personal injury lawsuits in the 1970s finally brought the health consequences to light. Use of asbestos insulation faded in the 1980s and ended by the 1990s.

Military use of asbestos insulation spanned from the World Wars to the Cold War, and the building and manufacturing boom of the 1950s and 1960s spread asbestos insulation throughout suburban homes and factories across the country. U.S. Navy ships, in particular, drove demand for asbestos to new highs, as miles of high-temperature pipes and many other components of naval vessels were wrapped and coated in asbestos insulation.

One of the titans of the asbestos insulation industry was created in 1901 when the H.W. Johns Manufacturing Company, famed for its asbestos-containing roof shingles, merged with the Manville Covering Company, which specialized in pipe insulation and operated its own asbestos mine. The resulting H.W. Johns Manville Company went on to become the largest manufacturer of asbestos products in the U.S. It reincorporated in 1926 as Johns Manville Corporation.

The young asbestos insulation industry enjoyed fantastic growth, but the warning signs were already apparent. Henry Ward Johns, who had given his name to the company he founded, died at just 40 years old of what a coroner then called “dust phthisis pneumonitis” — now believed to be asbestosis.

Asbestos has been used since ancient times to make fireproof cloth for the burial shrouds of kings and the tablecloths of wealthy landholders, but the modern asbestos industry did not arise until the machinery of the Industrial Revolution created a great need for insulation materials.

In 1828, asbestos was used in a steam-engine lining. It was the first asbestos product patented in the U.S. As boilers and high-temperature pipes became increasingly common fixtures in businesses and vehicles during the 19th century, asbestos insulation products gradually proved their effectiveness, finally going into commercial production on a mass scale by 1874.


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