What Is Mineral Wool?

Mary McMahon

Mineral wool is an industrial product available for use in insulation and fire stops. It is produced artificially with the use of molten rock or furnace slag that can be spun to create a dense, wooly material that may be treated in a variety of ways for different uses. It comes in a loose fill format as well as a blanket style, allowing technicians to cut blankets to size for insulation; molded products for pipes and other objects are also available. Manufacturers may be able to produce custom components on request from customers, depending on the nature of a project.

Protective garments may be necessary when working with mineral wool.
Protective garments may be necessary when working with mineral wool.

This product has a number of properties that make it useful for insulation. It is fire resistant, and may be installed for fireproofing or to create fire resistant barriers in structures that contain flammable materials and other fire hazards. It also blocks sound and can be used to make sound booths or to limit noise from a factory floor. Mineral wool insulation can also be useful for differential temperature control in buildings where different environments may have their own heating and cooling needs.

Mineral wool fibers may enter the eyes and cause irritation.
Mineral wool fibers may enter the eyes and cause irritation.

Loose fill can be blown or piped into walls and other structures to create insulation. Batting can be installed like other forms of sheet insulation, and can also be wrapped around objects of interest like chemical tanks. Molded forms of mineral wool can be snapped over pipes and other objects to create a snug insulating barrier to limit heat loss or transfer, depending on the setting.

Fibers from mineral wool can enter the lungs and create irritation.
Fibers from mineral wool can enter the lungs and create irritation.

Home improvement stores may sell mineral wool and can also order it for specific applications. For industrial projects, contractors may order directly from manufacturers and wholesalers to cut costs. Companies that specialize in blow-in insulation and related products can obtain a range of mineral wool types for different applications, all rated in terms of the level of insulation and protection provided. This product can be used in new construction as well as retrofits and remodels, and meets insulation standards set by regional building codes.

Products derived from rock are known as rock or stone wool, while slag wall uses furnace slag as the raw material. Mineral wool is a potential irritant and needs to be handled with care. Protective garments, eye wear, and respirators should be worn while working with this product. Fibers can enter the skin, lungs, or eyes and create irritation and discomfort. Prolonged exposure may lead to chronic inflammation and other health care problems.

A roll of mineral wool insulation.
A roll of mineral wool insulation.

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Discussion Comments


@irontoenail - I feel so bad for you as a kid! That stuff is horrible to get in your skin. It's not a chemical irritant, which is good in some ways, but not so good in others, because it means all you can do is wait for the fibers to come out and wash the area.

It's basically hundreds of very thin, tiny needles being inserted into your skin. It feels like being brushed by one of those cactus with the thin spines.

So, yeah I wouldn't recommend it. Although in general, mineral wool as a batt insulation material is fantastic and I like that it is basically made from recycled industrial waste.


@irontoenail - It's a good thing you didn't keep playing with it, because I've heard that long term exposure can lead to people getting cancer.

I imagine that means people who work with these kinds of insulation materials though rather than just getting exposed to it once. But kids can be more vulnerable to these sorts of things, so who knows?

It's a good cautionary tale. I think it's another reason, too, to warn kids away from construction sites, or abandoned buildings. You never know what they might end up getting exposed to.


I had no idea that rockwool was made from actual rocks.

I remember when I was a kid, my parents were doing a bunch of renovations on the house and they brought in a couple of pallets of mineral wool to use for batting.

They were all bundled up in plastic, so my parents didn't realize they needed to warn us away.

Being kids, we almost immediately realized that these were basically big soft cushions, perfect for jumping on.

Of course, until one of them burst and we all got itchy, painful skin.

Luckily none of us breathed it in or anything, but needless to say, our parents were very annoyed.

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