Install cavity wall insulation

Priority for Completion: High

This recommendation is made when an assessor finds cavity walls in a property of an age suggesting that they have not been fully insulated and they are unable to find evidence that they have been fitted with retro-fit insulation.

We have rated this improvement as one of high priority for completion. Retro-fitting cavity wall insulation requires a specialist contractor but is generally low cost and pays back quickly. It can have a major impact on reducing heat loss from your home.

What is cavity wall insulation?

Cavity walls have an air gap in the centre between the masonry layers. This gap was originally introduced to prevent damp transferring through the wall but it was quickly discovered to also help insulate the wall. Cavity wall insulation fits into this gap and acts to further prevent heat loss from your home.

The Energy Saving Trust has found that one third (33%) of the heat loss from an uninsulated house is lost through uninsulated cavity walls. This means that the potential savings are high.

Other considerations

Whilst the majority of homes are suitable for retro-fit cavity wall insulation, there are some circumstances where it is not appropriate. Unfortunately the current Energy Performance Certificate system does not normally allow this to be considered so your EPC may suggest cavity wall insulation even where it is not suitable. Always choose a reputable installer who will be able to advise on the suitability of your property, the best type of insulation to use and any other work which may need to be completed first.

The installer you choose should be a member of one of the following organisations:


Check that the installer is signed up to a code of professional practice and that the installation is guaranteed for 25 years by CIGA, or through an independent insurance-backed guarantee.