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What Is Glass Wool?

Mary McMahon
By
Updated: May 17, 2024

Glass wool is an industrial product made by spinning glass into a fibrous material that can be packed in mats and blankets. This product is used as insulation and in other applications, like for air filters. It is available through home supply stores and manufacturers can also produce wools for special purposes, like insulation in aircraft, where the standards may be higher for health and safety reasons. Numerous companies make glass wool products along with lines of other insulation materials for a variety of applications.

This product is made from molten glass mixed with a binder and forced through a fine sieve to turn it into delicate spun fibers. The fibers can readily mat together, and may be packaged in pre-cut batts or rolled blankets. Blankets allow users to cut the glass wool to size for the given application, while batts can be useful for standardized construction. Some glass wool products have a backing made from paper to make them easier to handle. The paper may include markings discussing the grade and type of wool for the convenience of workers.

For basic insulation in homes and other structures, this product can provide adequate loft and depth to limit heat transfer and block some sound as well. It is also possible to purchase special-purpose glass wool designed as acoustic insulation for activities like building sound booths or soundproofing a house in a noisy location, like next to a freeway. Other specialty products are used in aeronautics applications, and as insulators for equipment like batteries.

The glass wool is strong, durable, and resistant. It can potentially become a home for microbial growth if it gets wet, but otherwise should resist mold and other issues. In applications like construction, it is typically applied in walls wrapped with Tyvek® and other materials, which successfully keep water out of the building envelope. Special-purpose products are even more durable and can withstand harsh conditions.

Workers handling glass wool must exercise caution. It is an irritant that can cause itching and discomfort if it comes into contact with the skin, mucous membranes, or eyes. It can also cause lung problems if inhaled. Protective gear, including long sleeves, gloves, eye protection, and a respirator, is a good idea when handling this insulation product, particularly special-purpose products because of their increased strength. If someone does develop symptoms of exposure like itching or wheezing, it is advisable to consult a doctor.

About Mechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a About Mechanics researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By anon349696 — On Sep 28, 2013

It is also a very good insulator for HVAC systems.

By indigomoth — On Jan 11, 2012

@umbra21 - Another good place for the stuff is in attic insulation, particularly if your attic isn't used very much. If it's basically a storage space in the roof, you can pop some glass wool pads up there to stop heat from escaping through the roof of your house.

Most modern houses are built with insulation, but you'd be surprised how many older houses don't have it. Particularly in places which get cold, but not freezing cold, since it's not a necessity, so people just don't bother.

But heating bills can be really high in a house with no insulation.

It really makes a huge difference if you put even the smallest amount in and the attic is a good place to start since you probably won't have to tear out the walls to get it there.

By umbra21 — On Jan 10, 2012

We always called this rockwool. It makes pretty good pipe insulation if you want a quick way of bringing down your electric bill.

You just buy a few pieces of it, and stick it in around the hot water heater and as far along the pipes leading from it as you can.

Usually they only work as hard as they need to to keep the water at a certain temperature, so if you can help keep it there by using insulation, they won't need to use so much power.

By pastanaga — On Jan 10, 2012

When I was young my parents decided to do up the basement and wanted to install insulation before they put up the walls.

They bought the glass wool insulation long before they planned to use it and left it in stacks in the basement.

They told us to keep away from it, but didn't really explain why and it didn't take long before we realized that it was basically a pile of what seemed like plastic covered mattresses, just perfect for play.

We jumped all over those things, and built forts with them and so forth and always wondered why our skin was so itchy. I think we decided the dog must have fleas or something.

Eventually we burst a hole in one of the bags and dad realized what was going on. We got a spanking for that although, frankly, the itching was much worse and we were lucky we didn't get a lungful of glass.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

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