Kiwa Watertec

Kiwa introduces new cavity wall insulation installer assessment

  • 31 May 2017

Kiwa BDA has introduced a new cavity wall insulation installer assessment and surveillance scheme to provide customers with the assurance they are entitled to.

In order to reduce the amount of energy consumed by domestic buildings, about 50 years ago, insulation manufacturers developed systems that involved injecting insulating material into the cavity walls of existing houses, as well as systems that could be built or injected into the cavity walls of new build houses as they were being constructed.

However, introducing a material into the cavity wall might allow damp to cross from the outer to the inner leaf. Therefore, it is vital to ensure quality installation to mitigate this risk.

The quality of installation is easier to monitor with new build housing, with project architects, clients, site foremen and building control all playing their part. Most built-in systems are “partial fill’, with a cavity retained between the outside of the insulating material and the inside face of the external wall.

Some full fill built-in systems were introduced over the years, but from the very beginning injected cavity wall insulation was full fill.

It is much more difficult to monitor the quality of installation when the material is being injected into a cavity that requires specialist equipment to be seen. Consequently, the industry responded with the certification of systems and their installers.

Originally, polyurethane foam was used but this was overtaken by the expanded polystyrene bead and mineral fibre systems used today.

Over the years it became clear that some properties were not suitable for CWI, and quality schemes were updated to take account of this. Even now though, BBC News carries details of damp penetration in houses in Lancashire allegedly due to faulty CWI.

Kiwa has developed new approval schemes for injected systems and their installers and has recently awarded BDA Agrement to System Designers including Warmfill, Moulded Foams, Thermabead and Energystore. These documents are easily accessible via the website.

Thermal performance, resistance to moisture penetration, adequacy of fill, condensation risk and durability have all been assessed. The approvals cover the use of the systems in the UK and the Irish Republic where applicable, all subject to consideration of the location of the installation and degree of exposure.

The System Designer must approve the installer in the first instance, and there is an on-going rigorous and thorough independent check in the form of the Kiwa Installer Assessment and Surveillance Scheme to address installer competence via training and qualifications, as well as site practice – all verified by site and office inspection.

Properties under consideration for CWI must be surveyed thoroughly before any material is installed. A check-list assessing the exposure of the location, the layout of the property, details of its construction, chimneys and heat-producing appliances and type and position of the damp proof course must be completed. In addition, the topography and age of the property needs to be established and described.

The condition of windows, doors and rainwater systems must be reported and any damage to render or defects in masonry, such as spalling, loose mortar joints or damage due to failed or failing services must be noted.

The wind-driven rain conditions typically experienced by the property, using the guidance given in BS 8104 and relevant national Building Regulations, must be assessed. BRE Report 262; thermal insulation avoiding risks in walls up to 12m high should also be consulted. Gradings run from Sheltered – less than 33 litres per rain spell to Very Severe – 100 or more litres per rain spell.

A borescope investigation should be carried out at survey stage to look at the condition of the cavity. Any remedial measures required should be set out and must be completed before any CWI measures are undertaken.

If the property is considered suitable for CWI, the surveyor will detail the drilling pattern from the System Designers’ Installation Guide and determine the volume of material required.

The leader must document details of the fill material and equipment used, as well as on-site test data, once the installation has commenced. When completed, the installer must then sig off the job and declare that the work has been undertaken correctly and all necessary checks have been carried out.

All documentation should be retained and is subject to audit by Kiwa inspectors.

The Kiwa scheme provides the customer, whether developer, housing association or householder with the assurance they should be entitled to.


Kiwa UK Group
Kiwa House,
Melvern View Business Park,
Stella Way, Bishops Cleve,
Cheltenham.  GL52 7DQ

Tel: +44 (0)1242 677877

Visit the Kiwa BDA website

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