Mineral Wool Insulation Pros and Cons

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R-values of loose-fill insulationThere are three main types of conventional loose-fill insulation used in the walls and ceiling of residential and commercial buildings: fiberglass, cellulose and mineral wool. Each has certain advantages and disadvantages. This article looks at the third of the three – mineral wool insulation.

What is it?

Mineral wool is a fiber insulation like fiberglass, but it is made of natural materials instead of glass. There are two types of mineral wool: rock wool consists of fibers of natural stone (basalt or diabase, for example); slag wool consists of fibers made from iron-ore waste. It is sold in batts and as loose-fill, just like fiberglass. Mineral wool was, for many years, the most widely used type of insulation in North America and Europe.


  • Mineral wool is naturally moisture-resistant. It retains its insulating qualities even when wet.
  • Sound is blocked much more by mineral wool, so the interior of a building suffers less acoustic invasion .
  • Mineral wool will not burn until temperatures reach beyond 1,800°F (1,000°C). The insulation actually performs as a fire barrier, slowing down house fires and giving the fire services more time to get things under control.



  • Protective gear must be worn when installing mineral wool insulation: the tiny slivers will lodge in skin and are small enough to be inhaled.
  • Inhaled slivers of mineral wool irritate the alveoli and can cause lung disease.
  • There is some data which suggests mineral wool slivers in the lungs may cause cancer, by slicing DNA and causing cell mutation, in the same way as fiberglass.