Glass wool

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Glass wool is an insulating material made from fibres of glass arranged using a binder into a texture similar to wool. It also features raw materials including silica sand and limestone. The process traps many small pockets of air between the glass, and these small air pockets result in good thermal insulation properties.

It is available in a range of densities and as such has varying levels of thermal conductivity. It is typically used in masonry cavity walls, timber frame walls as roof rafter insulation and in loft and suspended floor applications.

The product has good acoustic and reaction to fire properties and uses post-consumer waste in its manufacture.


Masonry cavity walls
Timber frame walls
Rafters and lofts
Suspended floors


Good acoustic properties
Uses post-consumer waste
Good reaction to fire properties

PIR = Superior thermal performance

Because of its superior thermal performance PIR insulation offers optimal insulation value meaning a thinner layer will achieve the same insulation properties.  This has other benefits, as using thicker insulation will mean a larger building footprint or smaller internal dimensions for a property.

The diagram shows the typical thicknesses of different wall insulation materials needed to achieve an R value of 4.5.