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Walls

Mineral wool

Mineral wool is insulation made from glass or stone fibres, sold as batts, rolls or loose fill and used to fill the cavities between studs and joists.

Also known as mineral wool insulation, glass wool, stone wool, rock wool, insulation batts

Glass wool is spun from molten glass and recycled glass, stone wool from volcanic rock. Both trap air between fine fibres, which gives low thermal conductivity, and both are non-combustible and good at absorbing sound. Stone wool is denser and often chosen where fire or acoustic performance matters most.

In a timber-framed wall the insulation fills the stud cavities completely, without gaps or compression, because every void is a thermal bridge. Batts are cut to the cavity width; loose fill is blown in to a set density.

Related terms
Blown-in insulationBlown-in insulation is loose insulation material (cellulose, glass or stone wool) blown into a cavity until it fills it to a specified density. Wood fibre insulationWood fibre insulation is made from softwood fibres, as flexible batts, rigid boards or loose fill, and is used in walls and roofs as a bio-based alternative to mineral wool. U-valueThe U-value measures how much heat passes through a building element, in watts per square metre per kelvin (W/m²K); the lower the value, the better it insulates.
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