Low Energy House

Low Energy House - What is Glass Wool Insulation?

Glass wool insulation is manufactured by the ‘Crown Process’ from sand, lime and soda ash, with recycled glass added

Glass Wool Insulation - Loft Insulation - Image Provided by Knauf InsulationProduction of Glass Wool Insulation

The raw materials are melted in a continuously operated furnace at temperatures around 1550 degrees C. The liquid flows from the furnace through a series of channels known as forehearths.

From the forehearth, the glass flows by gravity into a rapidly rotating alloy steel dish or ‘Crown’ which has  several hundred fine holes round its periphery. The molten glass is thrown out of the holes by centrifugal force to form filaments which are blasted with high velocity hot gas to increase the fineness.

The resulting mat of fibres is then coated with resin to bind it together. After passing through an oven, which cures the resin, the mat is then cut to individual blankets or quilts that are rolled and packed.

Recycling Glass Wool Insulation

Manufacturers of glass wool insulation can replace around 50 per cent of their raw materials with recycled glass, which leads to energy savings in the production process and reduces demand for quarried raw materials.

Forms of Glass Wool Insulation

The density of the product determines what form the insulation takes. Glass  wool insulation is available in various forms:

  • lightweight quilt rolls, either unfaced or faced with polythene, for use in roofs, within timber-frame construction and inside floors.
  • loose fibre for hand filling or blown for cavity filling and loft insulation
  • batts and slabs for complete cavity filling of new masonry walls
  • semi-rigid slabs for the partial cavity filling of new masonry walls
  • laminates of rigid glass wool and plasterboard for dry lining

Physical Qualities of Glass Wool Insulation

Glass wool insulation is lightweight and its long strand fibre gives good tear strength. It is non-combustible, water repellent and rot proof. Glass wool insulation can withstand temperatures of up to 230 degrees C and is non -combustible.

Thermal Performance of Glass Wool

Three layers of 100mm (300mm thick) glass wool insulation batts in a loft floor will achieve a very low U-value of 0.11 W/m²K

The thermal conductivity of glass wool insulation products typically ranges between 0.040 and 0.031 W/m K at 10 degrees C.

In the UK, when comparing the thermal values of insulation materials, it is important to remember that the best performing material is the one with the lowest thermal conductivity value

About Glass Wool Insulation - Loft Insulation - Cavity Wall Insulation