Cavity Wall Insulation With E.P.S. Beads

Cavity wall insulation involves the injection of a suitable insulant, using a specified and approved system designed to ensure a complete fill of the cavity wall area.

undefinedThe Cavity Insulation Guarantee Agency provides independent 25 year guarantees for Cavity Wall Insulation fitted by registered installers. The Cavity Insulation Guarantee Agency was established in consultation with the Government to provide householders with an independent, uniform and dependable guarantee covering defects in materials and workmanship. Independent research has confirmed that cavity wall insulation is a very reliable process. Problems are therefore extremely rare, but if they do occur, CIGA has the expertise to ensure that they are swiftly rectified.

Composition & Durability

Cavity Wall InsulationThe polystyrene used for CWI is in the form of virgin pre-formed bead which is usually combined with a binding agent or adhesive at the time of injection. Polystyrene beads are produced to a specified size and density which remains unaltered during the installation process.

The materials are produced under strict quality control to ensure compliance with the performance requirement of the appropriate British Board of Agreement Certificate.

The installation must be carried out in accordance with the relevant BBA Certificate, their surveillance scheme, the System Suppliers installation Manual and all CIGA guides to best practice.

Once installed, the bead filling in the cavity will remain an effective insulant for the life of the building and will require no further maintenance.


Thermal Conductivity: The k value of white expanded polystyrene bead should be taken as 0.038 W/m C - 0.040 W/m C (ref. individual BBA Certs)
The k value of Carbon (Grey) expanded polystyrene bead should be taken as 0.032 W/m C - 0.034 W/m C (ref. individual BBA Certs)

Density: A typical installed density is 12kgm3 +/- 2kgm3 (ref. individual BBA Certs)

Fire: The use of polystyrene bead for cavity wall insulation does not prejudice the fire resistance properties of the wall.

Water: The material is resistant to water penetration and will not transmit water across the cavity by capillary action or from below dpc level. Any rainwater penetrating the outer leaf will drain harmlessly to the footings. The product is not designed to be a water vapour barrier.


Survey: A pre-installation assessment is carried out to determine the suitability of the property for cavity wall insulation.

Preparation: Internal and external checks are carried out by the Technician prior to installation. Injection holes are drilled in the external wall of the cavity as specified by the relevant BBA Certificate and System Suppliers manual. Typically holes are drilled around the upper part of the building only and below windows and lintels. The cavity at any party wall line is sealed with a closure approved by the BBA for the purpose.

Installation: The polystyrene beads are injected into the cavity via an injection gun in a specified sequence to ensure a complete fill of the cavity.

Making good: Following the installation the injection holes are made good to match the original wall surface as closely as possible.

Post Installation Check: All fuel-burning appliances and their flues or source of air supply are checked to confirm their effectiveness.

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