Asbestos Content in Mineral Wool or "rock wool" ?

Is there asbestos in Johns Manville Spintex mineral wool, Gyproc Wool, Rock Wool Manufacturing Co. & other stone wool, rock wool, slag wool products?

Do Rock Wool, Slag Wool, or Mineral Wool Insulation contain asbestos fibers?

Mineral wool insulation, slag wool insulation, and "rock wool" building insulation either in batt form or as loose fill would, in almost all cases, not be expected to contain asbestos fibers.

There were a few exceptions but those are not likely to be found as ordinary building insulation.

There were some mineral wool products that deliberately combined asbestos, such as layers of asbestos paper, with mineral wool, and other inventors experimented with combining other fibers such as flax with mineral wool to reduce its tendency to settle in vertical installations such as wall cavities.

Below you'll find our references to asbestos combined with mineral wool building insulation by an the Alabama Rock Wool Manufacturing company.

Do Old Rock Wool Blankets Residential Home - contain asbestos?

Do old Rock Wool blankets (kraft or foil faced insulating batts) contain asbestos? As described by an InspectApedia.com reader:

These insulating blankets are quite heavy, filled with what looks like reddish brown dirt and tiny pebbles and tiny pieces of fiber, paper covered with a blue or black manufacturer's label box framed picture of a house on the right and instructions on the left that states Rock Wool above it.

I'm not sure of the date it was installed. My father and uncle could have installed it in or after 1975 when my mom and dad and my uncle's family purchased the place, or it was installed by the original owner.

I'll have to check the deed to see when the house was built. My sisters and I inherited the summer home which is in Espyville, PA.

About four years ago I got permission from my family to begin remodeling.

I was so excited to do the job that I began pulling the paperboard ceiling and walls on the second floor without thinking and out plopped one of these blankets that broke open spewing dust into the air. I stopped immediately.

After returning home, I tried to find this insulation on the Internet. I did find an old homes and historic homes site that had an exact picture of it and the manufacturer's label that looked identical and it stated that this type old insulation does not contain asbestos.

I found another site that stated some old Rock Wool insulation did contain asbestos, but this type was only used in high heat applications on hydronic piping, and not likely in residential attic/wall applications.

I convinced myself that I would be OK for I was anxious to remodel and my brother in law and I continued the job wearing only paper masks. It sure was a dirty job.

The second floor only has two bedrooms, but I was surrounded in dust.

I did open the Florida windows and placed a fan inside for ventilation, waited for some dust to dissipate out of the windows, took frequent breaks to fresh cool outside air when the heat and dust got to be too much. also doubled up on the paper mask when I noticed dust was getting below a single mask and frequently changed masks.

But I don't know what good those paper masks did for me if at all. It took us two (6 hr days) and one (4 hr day) to complete removing the wall and ceiling boards and insulation (only one bedroom had this insulation).

Then my sister and I went there the following weekend to wash things down and place fiberglass insulation (6 hr job). All and all I would say I exposed myself to about 12 min. to 18 max. hours to Rock Wool dust using only paper masks.

Now I'm worried sick from seeing Mesothelioma commercials making me check more sites on the net and found sites that state some old Rock Wool blankets can contain asbestos.

What to do? Please help with any knowledge of old Rock Wool. Meantime I'm going to see if I can find some of it on the first floor and have it tested. I don't have any health symptoms, but I am going to make an appointment with my doctor anyway and get a ct scan for peace of mind. Thank you very much for your help, J.C. - (July 25, 2011) JC

And from another InspectApedia reader:

I found Gold Bond rock wool name on it. I think the manufacturer is or was in Buffalo New York. Does it contain asbestos just like the picture above?

Its the same as the picture above - (Dec 5, 2012) Mike

Reply: Normally mineral wool or "rock wool" slag wool or stone wool insulation does not contain asbestos but there are exceptions

It would be unusual for a residential home to have rock wool insulation containing asbestos - to know with absolute certainty I'd have a sample of the insulation tested.

Shown here: photographs of Gold Bond™ brand mineral wool insulation in a 1960's Haddonfield New Jersey Home.

A more immediate concern is doing any construction demolition involving lots of dust and debris without wearing adequate HEPA-rated filtered respirators.

Acute exposure or chronic exposure to many if not most dusts can lead to lung and eye irritation and adult onset asthma. And of course if the building dust was contaminated with bird droppings, rodent droppings, or similar, there may be bacterial or viral hazards too.

If you are having respiratory distress you'll want to go to your primary care physician, discuss your concern and case history, and most likely the doctor will refer you to a pulmonologist for some simple lung tests, or to a doctor specializing in environmental medicine.

Bottom line: According to a 1980 US EPA study the principal airborne hazards associated with mineral wool products were in its manufacture.

Also see MINERAL or SLAG WOOL HEALTH EFFECTS

• U.S. EPA, SOURCE CATEGORY SURVEY: MINERAL WOOL MANUFACTURING INDUSTRY [PDF] U.S. Environmental Protection Agency, Office of Air, Noise, and Radiation, Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina 27711 (March 1980)

Examples of Asbestos Use in Mineral Wool Products

A look at mineral wool patents between 1900 and 1930 finds hundreds of patent citations: there was a lot of activity for blowing mineral wool from slag, for making mineral wool felt, for numerous heat-insulating applications. Below are a couple of examples. Other research its cited throughout this article series.

Of interest was research on combining mineral wool with other fibers such as flax (which didn't settle) in an effort to reduce settling in walls (Kelly Sept 1901). So indeed we might find some hybrid mineral wool or slag wool products.

And while mineral wool is not an asbestos material, some applications experimented with stitching asbestos and mineral wool together. (Kelly Feb 1901).

Not to worry, from reading the patent description the asbestos combined with mineral wool by Kelly (cited below) would have been recognizable as layers of thin sheets of stitched-on paper.

• Emrick, Frank C. "Insulating material and method of manufacturing the same." U.S. Patent 1,426,163, issued August 15, 1922.
• Gyproc Wool Insulation, produced by GYPSUM, LIME & ALABASTINE CANADA, LIMITED, 50 Maitland St., Toronto, Ontario, Canada, with facilities in Vancouver, Calgary, Winnipeg, Toronto, Montreal Canada, [illustration shown here] was advertised in The Lethbridge Herald from Lethbridge, 27 January 1950, p. 11.
  
  There is no mention of asbestos in this product.
• Hall, Charles C. "Process of making mineral-wool felt." U.S. Patent 737,099, issued August 25, 1903.
• Kelly, George. "Insulating and fireproof sheeting." U.S. Patent 668,684, issued February 26, 1901.
• Kelly, George. "Composite insulating material." U.S. Patent 683,208, issued September 24, 1901.
  Excerpt:
  
  The object of my invention is to produce a sheet of the character specified of natural fireproof materials-as, for instance, asbestos paper and mineral-wool fiber united in layers by means of stitching of novel form designed to retain the layers without pulling through the soft material, the uniting stitching or lines of stitches being disposed and arranged in a manner to facilitate the folding or rolling of the sheets into small compass for storage or transportation.

Asbestos Used by the Alabama Rock Wool Company

Insulating cement products using asbestos led to litigation and bankruptcy.

The original Rock Wool Company, (located in Leeds Alabama, founded in 1943) produced rock wool used for blown-in building insulation and other insulating products.

From about 1958 to 1970, as a new product line, the company added asbestos to rock wool to form insulating cement boards and other insulating cement-based products such as an insulating lagging or paste applied to heating pipes and possibly some heating boilers.

The principal exposure hazard was to workers of Rock Wool Co. where these products were manufactured.

- AF Cement

- Delta Maid High Temp Insulating Cement

- Delta Maid High Temp Mater-Cement

- Delt Maid One-Shot Insulating Cement

In 1994 Rock Wool was found guilty of producing "unreasonably dangerous products" and was required to pay damages. The company faced about 150,000 asbestsos-related lawsuits.

In 1996 the Alabama Rock Wool Company filed for Chapter 11 bankruptcy as a result of that asbestos-related litigation. In December 1999 the company emerged from bankruptcy to form the Rock Wool Asbestos Trust to settle various litigation-related claims.

The period for filing claims against the Rock Wool Company trust ended on 13 January 2011.

GLA Gyproc Wool Insulation Identification

Above: the "GLA Product" logo found on mineral wool insulation by our reader who commented:

I am renovating basement in Toronto Canada found those old insulation bags they look like they are from 1990s gyprock wool insulation reading this website I think it don’t contain asbestos we did since it do t have black tar paper and we did no disturbed it just worked around it - Johnny 8/21/2025

Earlier on this page we included advertisement sheets identifying mineral wool insulation produced by GLA and identified as Gyproc Wool Insulation. The Gyproc Insulation photos here were provided courtesy of our InspectApedia reader Johnny.

We explained that GLA - clearly identifies the 1950s company, cited in more detail in other of our responses to reader questions on this page and we emphasized that mineral wool isn't asbestos.

We noted, however, that there is a separate question about asbestos in other GLA products such as drywall - see

ASBESTOS in CANADIAN GYPSUM LIME & ALABASTINE GLA DRYWALL - GYPROC [Web page]

Above: GLA Gyproc insulation installation instructions imprinted on the product's kraft facing paper. GLA's first mineral wool insulation plant was built in 1936 at Caledonia, adjacent to its plaster mill. The new product was called "Gyproc Wool". Additional gyproc wool (Mineral wool) plants were constructed in 1942 and in 1947. By the late 1940s Gyproc Wool was being shipped from Caledonia to all of the Canadian provinces.

In 1950 an additional Gyproc Wool plant was completed in Calgary.

Here's a 1950's document from McGill University that gives some of the Gyproc and GLA Corporation and Mineral Wool Insulation history in this

1950 Annual Report for Gypsum, Lime, and Alabastine Company, Canada [PDF] - local copy saved as GLA-History-1950.pdf You'll see that GLA had facilities in Winnipeg( (Sales and Plaster and board mill), Gypsumville (Gypsum quarries), Calgary (Plaster mill and mineral wool plant), Vancouver (Sales office), Falkland (Gypsum quarries) and New Westminster (Plaster & Board Mill).

(The word "Asbestos" doesn't appear in this report).

Below: the GLA insulation fibers showing in this photo are difficult to distinguish from fiberglass vs. mineral wool.

Below: other insulation from the same home, with partial labeling and whose manufacturer we did not identify.

Properties & Contents of Johns Manville Spintex® Insulating Batts

Reader Question: Is there Asbestos in Johns Manville Spintex Batt Insulation? History & Properties of Johns Manville Spintex® Insulation

Does John Manville Aluminum Wrapped Spintex batt Insulation (with aluminum foil on one side and [brown kraft] paper on the other side) contain asbestos and what would be the R value.

The insulation is from the 1950's. There's a number on the aluminum side Hl-131B - Dan. 05/03/2015

This question was originally posted

at INSULATION INSPECTION & IMPROVEMENT

Reply: Most mineral wool insulation does not contain asbestos but there is at least one known exception from an Alabama manufacturer

The short answer is that all research we've made to date indicates that Johns Manville Spintex® batt insulation was a rock wool or "mineral wool" foil faced insulating batt product.

Spintex™ foil faced insulating batts produced by Manville were sold in thicknesses up to 6 inches.

Rock wool (or slag wool or mineral wool insulation) is not an asbestos material.

Watch out: however historical research cited below claims that asbestos was added to rock wool by at least one manufacturer, Rock Wool Manufacturing Company, in Leeds, Alabama.

Asbestos was added to the company's "rock wool" insulation for insulating value or as a binder according to sources cited below.

Also if mineral wool or rock wool was produced at a facility that also handled asbestos there is a possibility of some cross-contamination between the materials. So without a lab test one cannot absolutely guarantee that mineral wool or "rock wool" is asbestos free.

[Click to enlarge any image]

Spintex® was described as well as a "blown home insulation" in the form of Spintex batts and blankets. - Johns-Manville Corp.,

"Asbestos the Magic Mineral", [8 MB PDF] Johns Manville on the occasion of its 100th Anniversary, when in 1958 the company described its use of mineral slag (obtained as a byproduct from metal refining) beginning as early as 1928 and producing mineral wool. Quoting from that document,

The mineral wool is formed into small nodules and blown into the walls of older, uninsulated houses by special blowing machines. J-M mineral fibre products for home insulation include Spintex® Blown Home Insulation and Spintex batts and blankets.

These fibres are also used to produce insulations widely used in industry by manufacturers of home freezers, refrigerators, kitchen ranges, air-conditioning ducts, and many types of industrial products.

Johns-Manville plants manufacturing mineral wool products are located at Alexandria, Ind., Manville, N.J., Richmond, Inc., Watson, Calif., Waukegan, Ill, and Toronto Ontario. - [est. 1958] - retrieved 3 May 2015 original source http://www.scribd.com/doc/36151062/Johns-Manville-Document#scribd

The R-Value for Manville Spintex was about 4.8 per inch before allowing for the effects of insulation gaps or material inconsistencies.

See the illustration of this product from an October 1958 Life Magazine advertisement shown at above left.

Watch out: while Spintex® is a mineral wool or "rock wool" non-asbestos product, if it was produced at a location where asbestos products were also manufactured one cannot presume that there cannot possibly be any asbestos particles found in the material. However the lab test reports that we have reviewed have not confirmed asbestos in any rock wool or mineral wool samples.

Following are some research citations that explain the derivation of the "Spintex" term and how it was used to produce fibers and insulating products. I think the origin of spintex was a German invention (see Bechler (1947) and Eugen (1959) and earlier US Patents citing Rollenlager-Spindelfabrik Spintex GmbH, Stuttgart-Bad Cannstatt, Germany Application July 8, 1954 or earlier)

The term "spintex" described a process used to produce a spun fiber. See these citations describing Spintex Insulation and the spintex process as well as its applications. Adding to confusion about the term, Spintex Inc. continues as a Illinois corporate name in the U.S. as well as in Canada and in India.

Currently In the U.S. Spintex is an injection molding company with offices in the U.S. and Japan. In Canada Spintex is currently a furniture manufacturer in Alberta. In Bangaladesh Spintex is a textile manufacturer. And there are of course more users of the Spintex name.

Additional Photographs of Spintex® Insulation from Johns Manville, courtesy of reader DK.

Spintex H1-131B aluminum foil wrapped mineral wool insulation

Below: Johns-Manville Spintex Insulation, Long Fiber Rock Wool, H1-128-B

also provided by reader Dan, sampled from a home in N. Royalton, OH, USA.

Notice that JM's product facing identifies it as "long fiber Rock Wool" insulation.

...

Bulk sample images of these Spintex insulation samples will be followed by micro-photographs of these insulation products examined by transmitted and polarized light under the microscope.

Above: Johns-Manville Rock-Wool Insulation, black kraft-faced H1-128-B insulation, bulk sample.

Below: Johns Manville Rock Wool Insulation, silver or aluminum-foil faced H1-131-B insulation, bulk sample.

Also see MINERAL WOOL by MICROSCOPE

Forensic Lab Microscope Photos of Johns Manville Spintex Foil Faced Mineral Wool Insulation No. H1-131-B

These lab photos are arranged in order of increased magnification from about 10x under the stereo microscope up to 1200x under transmitted light microscopy using triacetin with phenol as a mounting fluid.

Using PLM microscopy we did not detect asbestos in these two samples of Spintex mineral wool.

and

and with a scale giving the diameter of one fiber

Below: lab photographs of Johns Manville Spintex black kraft-paper faced mineral wool insulation No. H1-128-B

[Click to enlarge any image]

and

Research on Mineral Wool, Rock Wool, Slag Wool & Asbestos in Mineral Wool Insulation

• "Asbestos in Alabama", Mesothelioma Center ( a website supporting litigation and health claims concerning asbestos exposure), Website: http://www.asbestos.com, retrieves: 2015/12/06, original source: http://www.asbestos.com/states/alabama/, Excerpts:
  
  ... Alabama has no history of mining asbestos, use of the fibrous mineral spanned multiple industries before it was recognized as a human carcinogen in the 1980s. ...
  
  In 2004, the Birmingham News printed a series of reports on the severity of asbestos problems in Alabama.
  
  One story detailed how Rock Wool Manufacturing, a cement manufacturer in Leeds, added asbestos to its products as a bonding agent.
  
  When unprotected workers handled the cement, they were exposed to the toxic substance. ... A July, 2010 report in the Huntsville Times showed that workers also found asbestos during a renovation of the Von Braun Center. ... in four sections of the building.
  
  Crews reported finding asbestos in the ductwork, in the floor tiles and in some exterior panels.
  
  Really? Where in that report of finding asbestos "in the floor tiles and in some exterior panels" does mineral wool or rock wool appear? And where and when did the Rock Wool manufacturing company ever produce floor tiles? - Ed.
  

• Alabama: Birmingham News, "The Business of Death - Rock Wool, a Bad Decision", retrieved 2015/12/06, original source: http://www.al.com/birminghamnews/asbestos/ [Note: The Birmingham News does not provide the actual article text online - Ed.] Quoting:
  
  The business of death: Rock Wool Manufacturing's decision to add asbestos to cement cost the company 140,000 lawsuits.
  

More recently RockWool products from the currently-existing (2024) Canadian RockWool Company are described just below. Note that documentation that we found for the Canadian Rockwool Company's products described below do not include the word "asbestos".

• RockWool Manufacturing Co., 8024 Esquesing Line, Milton, Ontario Canada L9T 6W Web: https://www.rockwool.com/ - The company currently produces a wide range of building insulation products.
  
  Customer service and delivery inquiries: 1-855-876-3755 (Direct) 1 (800) 265-6878 Email: cs@rockwool.com Technical product inquiries: 1-877-823-9790 (Direct)
  
  ROCKWOOL SAFE USE INSTRUCTION SHEET [PDF] (2022)
  
  Example products: Delta Marine Board, a semi-rigid mineral wool insulation used in marine applications, illustrated above as found for sale at https://www.generalinsulation.com/products/marine/marine-insulation/rockwool-delta-marine-board/
  and also
  Pre-Formed rock wool Searox PS968 NA Marine Pipe Insulation - shown below.

Other businesses with similar names such as Delta Thermal Services, Inc. (f. 1994) a specialist in pipe and ceramic spray insulation continue in operation.

Contact: Delta Thermal Insulation, 55121 211th Lane, Mankato, MN 56001 USA, Tel: (507) 388-0757 Web: https://www.delta-thermal.com/

In July 2024 we tried to access deltainsulation.com but only found "not authorized " error messages.

 

• Gold Bond Rock Wool building Insulation (photo above) is not likely to contain asbestos but other products from that company did, including some including the Rockwool name such as Gold Bond Rockwool No. 340 insulating cement.
  
  Photo above from a 1970's home in Haddonfield New Jersey. Some Gold Bond products sold between 1940 and the early 1980s contained asbestos.
  
  Gold Bond was a subsidiary of Nataion Gypsum. Both Gold Bond and National Gypsum filed for bankruptcy in 1990, establishing an asbestos settlement trust fund of $370 million to handle asbestos claims.
  
  See details about Gold Bond asbestos products and National Gypsum asbestos-containing products
  
  at ASBESTOS PRODUCING COMPANIES & TRUSTS

• "Rock Wool Manufacturing Company Asbestos Trust Agreement", retrieved 2015/12/06, original source: http://www.resasb.org/Pdf%20Docs/trustagr.pdf
  Excerpt:
  
  Rock Wool filed a voluntary petition for relief under Title 11 of Chapter 11 of the United States Code (the "Bankruptcy Code") on November 18, 1996

• TANSIL v. RAYMARK INDUSTRIES, INC. et al Defendant: KEENE CORPORATION, ROCK WOOL MANUFACTURING CO., RAYMARK INDUSTRIES, INC. Plaintiff: LESLIE SEATON TANSIL
• Bakhshi, Shiv K., Steven H. Williams, James W. Scott, Randall M. Haines, and Ralph D. McGrath. "Method for manufacturing a mineral fiber product." U.S. Patent 5,490,961, issued February 13, 1996.
  
  Bakhshi, Shiv K., Steven H. Williams, James W. Scott, Randall M. Haines, and Ralph D. McGrath. "Multicomponent filaments comprising glass fibers and synthetic fibers joining with melted synthetic fiber particles; uniform distribution, flexibility, impact strength." U.S. Patent 5,736,475, issued April 7, 1998.
• Bakhshi, Shiv K., Steven H. Williams, James W. Scott, Randall M. Haines, and Ralph D. McGrath. "Method for manufacturing a mineral fiber product." U.S. Patent 5,490,961, issued February 13, 1996.
• Bakhshi, Shiv K., Steven H. Williams, James W. Scott, Randall M. Haines, and Ralph D. McGrath. "Multicomponent filaments comprising glass fibers and synthetic fibers joining with melted synthetic fiber particles; uniform distribution, flexibility, impact strength." U.S. Patent 5,736,475, issued April 7, 1998.
• Bechler, Andre. "Bearing adjusting device." U.S. Patent 2,424,013, issued July 15, 1947.
• Eugen, Maurer. "Top rolls for drawing systems of ring spinning frames." U.S. Patent 2,873,484, issued February 17, 1959.
• Eugen, Maurer. "Drawing top rolls for ring spinning frames." U.S. Patent 2,927,349, issued March 8, 1960.
• Mossbeck, Niels S. "Reinforced pocketed spring assembly." U.S. Patent 6,295,673, issued October 2, 2001.
• Udayakumar, T. "Insulation Materials for Solar Heating Systems and Their Application." In Solar Water Heating Systems, pp. 129-132. Springer Netherlands, 1986.
• Patel, Mayur M., and Timothy A. Walsh. "Blower for lifting insulation pack." U.S. Patent 6,244,075, issued June 12, 2001.
• Rice, Richard E. "Heat-storage breather system." U.S. Patent 3,320,724, issued May 23, 1967.
  Labate, Samuel. "Porous Materials for Noise Control." Noise Control 2, no. 1 (1956): 15-72.
• Rutledge, Richard A. "Acoustical panel." U.S. Patent 3,948,347, issued April 6, 1976.
• Wegener, Ing Walther, and Dilp-Ing Willi Zahn. "Vergleich der Gesamt-und der Querstreuung verschiedener Spinnverfahren." In Vergleich des normalen mit verschiedenen abgekürzten Baumwollspinnverfahren in Bezug auf Gleichmäßigkeit und Sortierungsstreuung der Garne, pp. 20-42. VS Verlag für Sozialwissenschaften, 1956.

Interestingly, a current incarnation of Johns Manville produces mineral wool insulating batts (shown above), giving us yet another version of this long-used product. The company notes that this product has a melting point of 2000°F.

• Johns Manville, a Berkshire Hathaway Company, retrieved 2016/11/15, Website: https://www.jm.com/en/home-insulation/products/mineral-wool/
  Excerpt: Johns Manville mineral wool insulation batts delay the spread of fire between interior rooms and provide superior fire resistance in exterior walls
• Also see more research on mineral wool, slag wool, stone wool, rock wool, or rockwool at References or Citations