Mineral wool insulation in an atticAsbestos Content in Mineral Wool or "rock wool" ?
Johns Manville Spintex & asbestos in mineral wool, stone wool, rock wool, slag wool

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Rock wool or mineral wool insulation:

Was there asbestos found in mineral wool, slag wool also commonly referred to as rock wool used for building insulation? Properties of Johns-Manville Spintex® and other mineral wool products.

This mineral wool or "rock wool" insulation article discusses the asbestos content in mineral wool insulation products. The short answer is "no asbestos" but we found that there are exceptions and some mineral wool products indeed were combined with asbestos in paper or other forms.

This document assists building buyers, owners or inspectors who need to identify various insulation materials in buildings by simple visual inspection. We provide photographs and descriptive text of various types of mineral wool insulation and describe its properties, how it is made, health and maintenance concerns, and its insulating values.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Mineral wool or "rock wool" or "slag wool" building insulation properties

Johns Manville Spintex Mineral Wool Insulation (C) InspectApedia DKMineral wool insulation, developed in the 1850's, patented in 1875 in the U.S. and this material, also called rock wool or in some texts slag wool insulation remained in popular use in the U.S. up to the 1950's, and is still in use today (2008) in some new construction, in manufactured housing, and in special applications such as the insulation of low-slope roofed cathedral ceilings and scissors-truss roofs.

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

Mineral wool insulation, slag wool insulation, and "rock wool" insulation would not be expected to contain asbestos fibers - We have been unable to find reports indicating otherwise.

However as we replied to a reader question about mineral wool containing asbestos, beginning

at MINERAL WOOL - ROCK WOOL 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 read that we found some references to asbestos combined with mineral wool building insulation by an Alabama company.

Question: Old Rock Wool Blankets Residential Home - contain asbestos?

(July 25, 2011) JC said:

Rock wool insulation © Daniel FriedmanDo old Rock Wool blankets contain asbestos? The 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.

(Dec 5, 2012) Mike said:

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

Its the same as the picture above

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

Gold Bond brand Mineral Wool in a Haddonfield New Jersey Home in the U.S. (C) Daniel FriedmanIt 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.

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

Asbestos Use in Mineral Wool Products

Gyproc Wool insulation produced by GLA in Canada, at InspectApedia.comA 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. Here 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 would have been recognizable as layers of thin sheets of stitched-on paper.

Properties & Contents of Johns Manville Spintex® Insulating Batts

Johns Manville Spintex Mineral Wool Insulation (C) InspectApedia DK Johns Manville Spintex Mineral Wool Insulation (C) InspectApedia DK

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

05/03/2015 Dan said:

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

Johns Manville Spintex Mineral Wool Insulation (C) InspectApedia DK

This question was originally posted at INSULATION INSPECTION & IMPROVEMENT

Johns Manville Spintex Mineral Wool Insulation (C) InspectApedia DK

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

Johns Manville Spintex insulating batts - Life Magazine

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 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

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.

Research on Asbestos in Mineral Wool / Rock Wool Insulation

Contemporary mineral wool batt insulation from Johns Manville - at original:

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.


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