Glass wool insulation Glass wool insulation, also known as fibreglass, is made from glass fibres. Glass is heated to very high temperatures until it melts, and is then spun quickly to create fibres. These fibres are then bound together to be used as insulation. The glass fibres create pockets of air which act as barriers to prevent heat loss because air is a poor conductor of heat. Glass wool can be found in batts and rolls, loose-fill insulation and also within insulation boards. Mineral wool insulation Mineral wool, also known as ROCKWOOL or stone wool, is made from a selection of raw materials, such as stone and glass. These raw materials are treated in a similar way to glass, in that they are melted at high temperatures until they melt, and then they are spun to form fibres, similar to wool. This wool is then packaged up into batts, rolls or slabs.