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Mineral wool with cellulose inclusions from a 2002 home (C) Daniel FriedmanComposition of Mineral Wool Building Insulation

Ingredients in "rock wool" stone or vitreous fibers

  • POST a QUESTION or COMMENT about Rock Wool mineral fiber insulation & microscopic examination or identification of mineral wool fibers

Rock wool or mineral wool insulation composition:

This article describes the composition of mineral wool or slag wool insulation used in buildings.

We include images of Gold Bond rock wool and other newer mineral wool products both in place in buildings and at higher magnification under the microscope. Details given here also help identify and confirm mineral wool or slag wool in the laboratory as well as in the field.

We describe old-house or "antique" mineral wool insulation as well as modern mineral wool insulating products still used in buildings.

Our photograph at page top shows modern mineral wool insulation sampled in a home constructed in 2002. This mostly-white mineral fiber insulation includes cellulose (chopped paper including newsprint) fragments that you can see as red and blue particles.

These paper fragments and fibers are a minor constituent in mineral wool insulation, possibly added to reduce settlement or in some building samples these particles might be volunteer fragments from nearby cellulose insulation.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

What are the Constituents of Rock Wool or Mineral Wool Insulation? (it's not asbestos)

Gray colored mineral wool or rock wool insulation in a 1990s mobile home (C) InspetApedia.com Treibs

This mineral wool or "rock wool" insulation article series illustrates and describes mineral wool or "rock wool" and slag wool insulation materials. Rock wool or "rockwool" insulation is also called mineral wool and slag wool though there can be differences among the components of these insulations.

Phot just above: typical dark gray mineral wool insulation submitted to us by an InspectApedia reader.

Just to add to the confusion about what to call this insulation, the insulation industry calls a range of products "mineral wool" and includes under that name: fiberglass (a very different material), slag wool, rock wool, "rockwool", stone wool, and vitreous fiber.

And as we explain below, though that term has been widely used generically in scholarly research, ROCKWOOL®, a Danish stone wool insulation company has trademarked the term "rockwool".

Rock wool or slag wool is a naturally-occurring mineral fiber that looks like chopped white cottony material. (It may have originally been formed by wind blowing across streams of lava from erupting volcanoes.)

As we noted at our home page for this product, MINERAL WOOL - ROCK WOOL INSULATION

Mineral wool is produced by melting rock and slag using coke as a fuel. The molten minerals are spun into fine fibers using high-velocity spinning rotor and a stream or air or steam.

A binder is applied to the fibers that are then collected on a wire mesh conveyer. The mineral wool fibers are then cut or granulated and packaged for shipment or they are further cured with additional binder so that the resulting fiber blanket can be cut into insulating batts and in some products, combined with a vapor barrier or facing.

Mineral wool insulation l is currently produced in the U.S. in Indiana, North Carolina, Texas, and Washington State as well as being produced in other countries. We list some current producers of rock wool or mineral wool insulation at Reviewers, below.

In an attic rockwool is typically about 1 1/2 pounds per cubic foot in density. In building walls this material is installed in more dense sprays of four to five pounds of material per cubic foot.

At roughly 1.2 pounds per cubic foot, rockwool or mineral wool has an R-value of R-30 (heavier than fiberglass).

Rock wool as a building insulating material remains in active use in the U.S. and has been reported in application in the Southern U.S. in the mid 1980's and continuing at least into the mid 1990's. [Home Energy Magazine Online, July/August 1997].

Currently stone wool, to use a synonym, is also used in acoustic control coatings for noise control, marine applications, fire-resistant coatings or insulations, and in vibration control systems. In addition, a number of researchers have studied the horticultural use of "rockwool" citing its advantages in the control of certain pathogens that affect crop growth. This research is cited in detail

at REFERENCES.

Modern mineral wool, widely referred to as "rock wool", is a manufactured product comprised of a mix of limestone, slag waste from steel blast furnaces, and basalt or diabase. Typically but varying by manufacturer, mineral wool insulation is about 3/4 steel slag and 25% basalt rock. Some rockwool producers use nearly pure recycled steel slag.

Similar to the production of fiberglass, rock wool is manufactured by heating these materials and spinning them into fine fibers that are then often applied in a sprayed-on chopped fiber form. Unless product packaging (or on older mineral wool installations, labeled vapor barriers) is present it is almost impossible for a consumer to identify the original brand or source of stone wool or mineral wool fiber insulation that has been installed in their home.

Watch out: about mixing trademarked words in normal human speech. Within this article and at this article's REFERENCES section more than 50 scholarly citations as well as many reader inquiries make generic use of these terms: rockwool, rock wool, stone wool, mineral wool, and slag wool and vitreous fiber.

However Rockwool® is a registered trademark of Rockwool International. In this un-dated

ROCKWOOL® letter [PDF]

received on 11 November 2016 the company has asked that their term "ROCKWOOL" be used only to describe their own products and that the terms "mineral wool" or "stone wool" be used for other products not marketed by ROCKWOOL International.

ROCKWOOL® is a registered trademark of ROCKWOOL International A/S and should be distinguished by our readers from all of the more-generic names or other product names used in this article series.

Therefore we ask our readers, IF they know that their specific mineral wool product is not made by this company that they keep in mind and use other synonyms for this mineral-fiber-based insulation product.

...


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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: what is the composition of this 1990's fibrous gray insulation in my mobile home?

Gray colored mineral wool or rock wool insulation in a 1990s mobile home (C) InspetApedia.com Treibs

(July 28, 2019) David Treibs said:

I have a mobile home manufactured in the early 1990s and it has this great blown in insulation that appears to be fiberglass.

Do you have any information on what its composition is and what is the R-value of it.

This Q&A were posted originally at

FIBERGLASS INSULATION IDENTIFICATION & PROPERTIES

Moderator reply:

MINERAL WOOL - ROCK WOOL INSULATION - home

Is probably what you have. It is similar to but is not fiberglass; it's a spun mineral fiber.

You can compare the R-values of Mineral Wool or rock wool and other insulation products in the table found

at INSULATION R-VALUES & PROPERTIES


...

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MINERAL WOOL / "Rock Wool" COMPOSITION at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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Citations & References

In addition to any citations in the article above, a full list is available on request.

  • Cummings, J. M. "Possibilities for the Manufacture of Mineral Wool in British Columbia" [PDF], British Columbia Department of Mines, (1937)- includes tables comparing properties of various insulation and other materials to mineral wool and balsam wool, retrieved 12/6/2014, original source: http://142.32.76.167/Mining/Geoscience/ PublicationsCatalogue/MiscellaneousPublications/ Documents/PossibilitiesManufactureMineralWool1937.pdf
  • [1] Seattle Energy Code, Seattle Energy Code History, web search 12/6/2011, original source: http://www.seattle.gov/dpd/Codes/Energy_Code/Overview/history.asp
  • Adams, P. "Effects of increasing the salinity of the nutrient solution with major nutrients or sodium chloride on the yield, quality and composition of tomatoes grown in rockwool." Journal of Horticultural Science 66, no. 2 (1991): 201-207.
  • Awang, Y. B., J. G. Atherton, and A. J. Taylor. "Salinity effects on strawberry plants grown in rockwool. I. Growth and leaf water relations." Journal of Horticultural Science 68, no. 5 (1993): 783-790.
  • Awang, Yahya B., and J. G. Atherton. "Growth and fruiting responses of strawberry plants grown on rockwool to shading and salinity." Scientia Horticulturae 62, no. 1 (1995): 25-31.
  • Eparvier, Agnès, Philippe Lemanceau, and Claude Alabouvette. "Population dynamics of non-pathogenic Fusarium and fluorescent Pseudomonas strains in rockwool, a substratum for soilless culture." FEMS Microbiology Letters 86, no. 2 (1991): 177-184.
  • Fonteno, William C., and Paul V. Nelson. "Physical properties of and plant responses to rockwool-amended media." Journal of the American Society for Horticultural Science 115, no. 3 (1990): 375-381.
    Abstract:
  • Fuchs, J-G., Y. Moënne-Loccoz, and G. Défago. "Nonpathogenic Fusarium oxysporum strain Fo47 induces resistance to Fusarium wilt in tomato." Plant Disease 81, no. 5 (1997): 492-496.
  • Galera, Melvin Maaliw, Eulsaeng Cho, Enkhdul Tuuguu, Shin-Jung Park, Changhee Lee, and Wook-Jin Chung. "Effects of pollutant concentration ratio on the simultaneous removal of NH 3, H 2 S and toluene gases using rock wool-compost biofilter." Journal of Hazardous Materials 152, no. 2 (2008): 624-631.
  • Kim, K-A., W. K. Lee, J. K. Kim, M-S. Seo, Y. Lim, K-H. Lee, G. Chae, S-H. Lee, and Y. Chung. "Mechanism of refractory ceramic fiber-and rock wool-induced cytotoxicity in alveolar macrophages." International archives of occupational and environmental health 74, no. 1 (2000): 9-15.
  • Leeman, M., J. A. Van Pelt, F. M. Den Ouden, M. Heinsbroek, P. A. H. M. Bakker, and B. Schippers. "Induction of systemic resistance byPseudomonas fluorescens in radish cultivars differing in susceptibility to fusarium wilt, using a novel bioassay." European Journal of Plant Pathology 101, no. 6 (1995): 655-664.
  • Marabini, Anna Maria, Paolo Plescia, Dante Maccari, Francesco Burragato, and Mario Pelino. "New materials from industrial and mining wastes: glass-ceramics and glass-and rock-wool fibre." International journal of mineral processing 53, no. 1 (1998): 121-134.
  • Marsh, G., R. Stone, A. Youk, T. Smith, M. Quinn, V. Henderson, L. Schall, L. Wayne, and K. Lee. "Mortality among United States rock wool and slag wool workers: 1989 update." JOURNAL OF OCCUPATIONAL HEALTH AND SAFETY AUSTRALIA AND NEW ZEALAND 12 (1996): 297-312.
  • McCullagh, M., R. Utkhede, J. G. Menzies, Z. K. Punja, and T. C. Paulitz. "Evaluation of plant growth-promoting rhizobacteria for biological control of Pythium root rot of cucumbers grown in rockwool and effects on yield." European Journal of Plant Pathology 102, no. 8 (1996): 747-755.
  • Mihuta-Grimm, L., W. A. Erb, and R. C. Rowe. "Fusarium crown and root rot of tomato in greenhouse rock wool systems: sources of inoculum and disease management with benomyl." Plant disease 74, no. 12 (1990): 996-1002.
  • Postma, Joeke, Margarit JEIM Willemsen-de Klein, and Jan Dirk van Elsas. "Effect of the indigenous microflora on the development of root and crown rot caused by Pythium aphanidermatum in cucumber grown on rockwool." Phytopathology 90, no. 2 (2000): 125-133.
  • Olympios, C. M. "Soilless media under protected cultivation rockwool, peat, perlite and other substrates." In Symposium on Soil and Soilless Media under Protected Cultivation in Mild Winter Climates 323, pp. 215-234. 1992.
  • ROCKWOOL INTERNATIONAL [PDF document on rock wool sustainability, Rockwool International A/S · Hovedgaden 584 · 2640 Hedehusene · Telephone (+45) 46 56 03 00 · Telefax (+45) 46 56 33 11 , website: http://www.rockwool.com/, is a current manufacturer of mineral wool insulation products used for fire insulation, sound insulation, and building insulation.
  • Savvas, D., and F. Lenz. "Effects of NaCl or nutrient-induced salinity on growth, yield, and composition of eggplants grown in rockwool." Scientia Horticulturae 84, no. 1 (2000): 37-47.
  • Smith, Denis. Rockwool in horticulture. Grower Books, 1987.
  • 3/07: thanks to Gary Randolph, Ounce of Prevention Home Inspection, LLC Buffalo, NY, for attentive reading and editing suggestions. Mr. Randolph can be reached in Buffalo, NY, at (716) 636-3865 or email: gary@ouncehome.com
  • ThermaFiber, Thermafiber, Inc., 3711 Mill Street, Wabash, Indiana 46992, Toll Free: 888-834-2371 (U.S. & Canada) ; Phone: 260-563-2111, is a current manufacturer of mineral wool insulation products. http://www.thermafiber.com/ Web search 07/28/2010, quoting:
  • INSULATION TYPES [PDF] table of common building insulation properties from U.S. DOE. Readers should see INSULATION R-VALUES & PROPERTIES our own table of insulation properties that includes links to articles describing each insulation material in more detail.
  • In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested

    CONTINUE READING or RECOMMENDED ARTICLES.

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