Greengates Builders Merchants

Isowool Cavity Wall Insulation

Silicone impregnated glass mineral wool slabs providing thermal insulation in masonry cavity walls.


Isowool CWS is designed to be installed during construction in the cavity between two masonry leaves in external walls.

The slabs can be used either to fully fill the cavity, or alternatively as a partial cavity fill when held against the outer face of the inner leaf in conjunction with a minimum 25mm residual cavity.

The product is a non-combustible, silicone-impregnated glass mineral wool slab, supplied in a variety of thicknesses, in         1200mm x 455mm dimension compatible with conventional wall tie spacing.

Isowool CWS is composed of high quality glass wool, which is bonded with a synthetic, thermo-setting resin, silicone impregnated, to form a strong yet resilient insulating slab, which is easy to handle, cut and install.


  • Water repellent - BBA Certified for all exposure zones.
  • Can be used in multi-storey construction.
  • Completely fire safe - Euroclass A1 fire rating.
  • Durable - not easily damaged, in storage, during transport or during installation.
  • Long product life - will not age.
  • Long installed life - will tolerate structural movement and settlement.
  • Robust - fibrous faces will follow wall contours leaving no airspaces and edges of adjacent slabs will 'knit', leaving no penetrating air gaps.
  • Does not hinder the natural drying out process of the building.
  • Will not accelerate corrosion of steel, copper or aluminium.
  • Odourless, inert and fully compatible with all standard building materials and components.
  • Will not slump or consolidate.


Isowool CWS is a glass mineral wool product, manufactured from silica sand, the Earth’s most abundant naturally occurring mineral. Glass mineral wool is one of the most environmentally friendly insulation materials. Inorganic and completely inert, over 70% of the raw material used in the production cycle are recycled. This process does not include the use of, CFC’s,

HCFC’s or other environmentally damaging gases.

Thermal Performance

A cavity wall of brick outer leaf and a 100mm concrete block inner leaf finished internally with 12.5mm Gyproc WallBoard on dabs, and with Isowool CWS insulation batts completely filling the wall cavity. U-value calculation assumes 6.7% mortar fraction.

Acoustic Performance

Isowool CWS helps to reduce flanking sound transmission along wall cavities, particularly when used as a full cavity fill.

Walls incorporating Isowool CWS batts will therefore constitute an effective design to help meet acoustic Building Regulations requirements.

Contact Greengates Builders Merchants, Lancashire Today To Hear More!

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