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I received an e-mail from a homeowner concerned that his attic might have asbestos insulation. A home inspector pointed out that the insulation behind the upstairs knee-walls is called “something wool”. It’s old, dirty and fibrous and the inspector told him that it should be tested for asbestos fibers.
Mineral Wool Insulation
“Rock wool” is made from mineral fibers manufactured from stone and waste from mining . It consists of aluminum silicate rock (basalt), furnace slag and limestone or dolomite.
“Slag wool” is produced mainly from blast furnace slag with some natural stone.
The term for both types of this fibrous insulation is mineral wool. Mineral wool was the most common thermal insulation for residential use until the 1960’s, when fiberglass insulation become the standard. The raw materials are melted in furnaces and blown with air or steam over spinning drums or a centrifuge to create the fibers (picture making cotton candy).
Asbestos is a naturally occurring fiber that is mined. Since mineral wool is a man-made fiber, it does not contain asbestos. I’ve read about mineral wool, asbestos and resins mixed together to manufacture a couple specific industrial insulating products, but it’s not likely the kind of stuff used for residential insulation.
Other Insulation
“Balsam wool” is a shredded wood product, treated with borax as a fire-retardant. It’s considered a very natural product and does not contain asbestos.
There is one type of older insulation that has a significant possibility of being contaminated with asbestos. That is the loose, granular insulation called vermiculite. See this article on vermiculite and asbestos for more information.
Fiberglass and cellulose are the most common insulation installed in residential attics today. I have never read or heard of either containing any asbestos fibers.
Other than vermiculite, it’s actually quite rare to find thermal insulation in residential attics that contains asbestos. In those rare cases, the asbestos containing materials used for insulation were manufactured for some other purpose. It was likely brought home from work at a factory or salvaged from some other type of building. I heard one story of a worker at a ship-yard bringing the stuff home regularly and stuffing his attic full.
21 Responses to “Does Some Attic Insulation Contain Asbestos?”
I have a question regarding attic insulation in an older home outside of Detroit, Michigan, built in the mid to late 1950’s. Below some newer insulation, I found a 1″ layer of tan to toast colored fiber that looked like wool, bonded to black paper. Was wool used in that era or am I looking at something else? I’m an electrician and would like to avoid any hazardous materials such as asbestos, so knowing what I’m looking at would be helpful.
Please respond to my E-mail address with any information you might have.
Thank you,
Phil Szwedo
How can I tell if drywall has asbestos? Is it harder to cut than standard drywall? I have sometimes cut drywall that was extremely tough to cut.
I too am an electrician, doing lots of work in old homes. I’d like to minimize exposure but still have to make a living.
Excellent site, keep up the good work
I have encountered what appears to be a hardened, somewhat rounded, shiny, mostly black (with some silver) material in an older homes attic. Do you have any ideas of what this might be?
Thanks
Bill E., could you be describing vermiculite?
See:
http://www.oldhouseweb.com/how-to-advice/vermiculite-and-asbestos.shtml
Hello, I’m about to buy a house built in 1925. During the physical inspection i was advised that the attic may have asbestos material. Is this a problem? Should I be concerned?
My house has insulation that looks like slag wool but also has a great deal of heavy black sand in it. The sand separates when the insulation is disturbed.
I am concerned that the fiber part may contain asbestos but I can not find any discriptions of an attic insulation that contains the black sand. My house was built in 1937.
Please help identify this strange insulation.
Thanx
Harold
Harold - This is what I found on mineral wool:
Old style ‘rock wool’ insulation is made in a similar process, but the raw material was coal boiler and blast furnace slag. It is darker in color (usually gray), is much heavier, and contains a lot of impurities that appear as black specs and particles that did not form into spun fiber.
I think it is possible the black specs and your black sand may be the same thing.
Here is the website I got the description from.
http://www.energytechpro.com/demo-res/Building/Insulation_Types.htm
I have this rockwool insulation in my attic and through my research feel confident that it
is free of asbestos and carcinogens. Follow
regular safety precautions and wear a nice mask anyways.
Thank you for posting this very informative and helpful website. I worked with asbestos years ago, and it is important for people today to have this kind of information to avoid it and to have it handled correctly by licensed professionals when abating or encapsulating.
we are remodeling and older home and have come across vermiculite insulation in the parts of the wall. is one able to remove this themselves? i have heard that asbestos removal can be very expensive and we simply cannot afford to hire professionals but in the same regard, cannot afford to work with this dangerous materail either. any suggestions or direction
Asbestos is one hell of a health hazard that is why we have removed all asbestos based insulation in our homes.-~`
Does the attic insulation that has wood chips and the powdery white stuff contain asbestos?
Does insulation used now a days have asbestos?
I am remodeling a bathroom, and when I removed the ceiling dry wall, a cascade of “furrie” insulation came down. I am guessing it some type of rock wool. It is dark grey to mostly black, and resembles what poodle hair would look like after being clipped. There are no signs of any other material being mixed with it. Am wondering if asbestos is an issue. The House is fifty years old.
Thanks for your comments.
Regarding rock wool aka mineral wool you are probably right that in and of itself it does not contain asbestos, however have you ever considered the possibility of cross-contamination in older homes (30 to 100 years old) when the walls were sanded and the paints contained lead or asbestos or removal of old asbestos insulated pipes when they became old and started to leak, or removal of any other asbestos containing materials like old wall tiles from your home? And we have not even talked about mice droppings and the like.
Better safe than sorry, and for peace of mind, why not remove very old rock or mineral insulation and replace it with new fiberglass insulation? The R value will go up (the old rock wool was only about 3 1/2″ thick with an R value of about 10 to 12 compared to the new attic fiberglass insulation with a R rating of 40) as does your re-sale value?
Do I make sense or just wasting your time and money?
Vermiculite is easy to spot. It looks like little rocks of different colours that more than likely contains asbestos (but not always!).
It should be removed carefully by an experienced professional wearing a safety suit and it best be sucked out through the roof not indoors! Any openings to the indoor (attic doors, etc.) should be taped off properly. Do not attempt to do this yourself. It is not worth your and your families health.
If you don’t have the money and are planning to stay in your home and not re-sell it you may keep the vermiculite in you attic but don’t disturb it by entering your attic. Leave it alone. Moving it around is very unsafe.
Asbestos is very dangerous to the health, this material is already banned’;`
Those two pictures alone are worth reading this article! Finding information or good pictures of old slagwool insulation is difficult, and the brands are nolonger around. I have the exact insulation in my home (1946) and was looking for information on asbestos for that brand. Im relieved to find that there isn’t any added asbestos in that type of insulation. Now if only i would have been so lucky with my floor tiles, ceiling tiles, mastic, lead paint, etc…
By the way Asbestos has been banned for the use in North America, however there is a dirty little secret that we (Canada), im not sure of the U.S. is STILL selling asbestos by the boat load to third world countries (Africa, India, Asia, etc). Politicians will not address this issue because its a very HOT BUTTON political issue in the province of Quebec (french canadians). They are so proud of their asbestos industry that they renamed a town after it http://www.ville.asbestos.qc.ca/ (its in french).
asbestos is a lung killer but some countries are still using asbestos as a heat insulator .,;
The insulation in our attic was exposed because of leaking during the winter rains. The date of construction was about 1970 and the brand of the insulation is PREMIUM BRAND High Density BUILDING INSULATION. It is in large bags with an Indian Head Symbol on them.
The actual material inside is dark grey or black in color and looks like cotton in consistency and texture. Do you or anyone reading this article know if this insulation is dangerous in anyway as it has been exposed by the rains.