Celotex Isover

Glass Mineral Wool

Glass mineral wool is a type of mineral wool insulation. It is a flexible and fibrous insulation material that can be used as both thermal insulation and acoustic insulation in a range of different applications.

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When referred to generically, the material may be described as ‘glass wool’ or ‘glass fibre’. It is different from stone mineral wool insulation.

How is glass mineral wool insulation made?

A molten glass formulation is spun into fibres, which are then sprayed with a binder before being shaped into a blanket. The blanket is cured by passing it through a curing oven, where it is also compressed into its final shape. Finally, the material is cut to size and packed.

Glass wool can be supplied as either slabs or rolls depending on how the product will be handled and installed. The aim is to supply products that require very little cutting, and generate minimal waste. In addition, typically with ISOVER glass mineral wool up to 80% of the material is manufactured from recycled materials.

The manufacture of glass mineral wool insulation, including the testing and declaration of its performance characteristics, is covered by the harmonised European standard EN 13162.

What is the performance of glass wool insulation?

The glass wool manufacturing process creates a product with a random fibre structure, and the density of the fibres can be altered to create products with characteristics suitable for different applications, with benefits including:

  • Low thermal conductivity.
  • Acoustically insulating.
  • Excellent fire performance.
  • Easy installation.

The random fibre structure of glass mineral wool traps pockets of air, helping to reduce air pressure variations passing through the quilt and acting to dampen the energy of the sound. Density in itself is not a measure of performance. As well as acoustic insulation, the trapped air also acts to give the material its thermal insulation properties. Glass mineral wool insulation products also achieve the highest possible ratings when tested in accordance with British or European standards for fire performance. Most types of glass mineral wool can be classified as ‘non-combustible’ or ‘of limited combustibility’.

In what applications is glass mineral wool insulation used?

Glass mineral wool is a popular thermal insulation option for the external walls of buildings, including as a full fill masonry cavity wall insulation, or installed within a timber frame. It also features within both masonry separating walls and timber frame separating walls.

The Robust Details scheme, which outlines a variety of separating (party) wall constructions that can be used as an alternative to pre-completion testing, features both generic and proprietary glass mineral wool specifications to help achieve the stated performance.

Internal floors should be insulated with glass mineral wool to reduce sound transmission between adjacent rooms. Internal partition walls, whether constructed from timber studs or metal studs, must be constructed to comply or exceed national building regulation requirements. Going a little beyond that minimum requirement can result in a substantial improvement in occupant comfort.

In pitched roofs, glass mineral wool laid at ceiling level is a common loft insulation solution. It can also be fitted between rafters when building a ‘room in the roof’, maybe as part of a loft conversion project, to provide both thermal and acoustic comfort.

Glass mineral wool is also used significantly in the lagging of ductwork and pipework and other similar HVAC applications.


Insulation products to consider
Product Name Thickness Range Sizes Lambda
ISOVER Acoustic Partition Roll (APR 1200) 25-100mm Width 2x600mm, Length 9170mm-20000mm NA
ISOVER Acoustic Slab 50-100mm Width 600mm, Length 1200mm NA
ISOVER Cavity Wall Slab (CWS 32) 65-150mm Width 455mm, Length 1200mm 0.032 W/m.K
ISOVER Cavity Wall Slab (CWS 34) 75-150mm Width 455mm, Length 1200mm 0.034 W/m.K
ISOVER Cavity Wall Slab (CWS 36) 50-150mm Width 455mm, Length 1200mm 0.036 W/m.K
ISOVER Cladding Roll 37 120mm Width 1200mm, Length 5050mm 0.037 W/m.K
ISOVER Cladding Roll 40 80-200mm Width 1200mm, Length 4100-10200mm 0.040 W/m.K
ISOVER Climcover CR ALU2 40-100mm Width 1200mm, Length 3000-6000mm See datasheet
ISOVER Climcover Roll ALU2 25-50mm Width 1200mm, Length 9000-18000mm See datasheet
ISOVER Climcover Roll ALU2 Strong 25-50mm Width 1200mm, Length 7500-15000mm See datasheet
ISOVER Climcover Slab ALU2 40-50mm Width 600mm, Length 1200mm See datasheet
ISOVER Climcover Slab ALU2 Standard 40-50mm Width 600mm, Length 1200mm See datasheet
ISOVER Metac 50-200mm Width 1200mm, Length 3200-9300mm 0.034 W/m.K
ISOVER RD Party Wall Roll 75-150mm Width 2 x 455mm, Length 4000-8500mm 0.036 W/m.K
ISOVER Spacesaver 100-200mm Spacesaver: Width 1160mm, Length 5200-12180mm | Spacesaver Ready-Cut: Width 3x386 or 2x580mm, Length 5200-12180mm | Spacesaver Lite: Width 1160mm, Length: 3500-7000mm 0.044 W/m.K
ISOVER Spacesaver Plus 100-200mm Width 1160mm, Length 3500–7000mm 0.040 W/m.K
ISOVER Steel Frame Infill Batt 50-100mm Width 600mm, Length 1200mm 0.036 W/m.K
ISOVER Timber Frame Batt 32 50-140mm Width 570mm, Length 1175mm 0.032 W/m.K
ISOVER Timber Frame Batt 35 90-150mm Width 570mm, Length 1175mm 0.035 W/m.K
ISOVER Timber Frame Batt 40 90-140mm Width 570mm, Length 1175mm 0.040 W/m.K
ISOVER Timber Frame Batt 43 90-140mm Width 570mm, Length 1175mm 0.043 W/m.K
ISOVER Timber Frame Party Wall Roll 50mm - 100mm Width 1200mm Un-split, Length 6000mm - 12000mm 0.036 W/m.K
ISOVER Timber Frame Roll 32 90-140mm Width 2x570mm, Length 2700-4200mm 0.032 W/m.K
ISOVER Timber Frame Roll 35 90-140mm Widths 2x570mm, 3x400mm (140mm only), Length 4000-5300mm 0.035 W/m.K
ISOVER Timber Frame Roll 40 90-140mm Width 2x570mm, Length 6500-10130mm 0.040 W/m.K
ISOVER Unislab 50-140mm Width 400mm or 600mm, Length 1200mm 0.036 W/m.K