Action Surrey: Surrey's Low Carbon Community

Call us:

Insulation: Cavity Wall

Install cavity wall insulation and save up to £480 a year*

Approximately 1/3 of the heat from a home is lost through the walls. Insulation between the walls helps slow this transfer of heat from the warm air inside the property to the cooler outside air. Cavity wall installation is quick and can take only a couple of hours depending on the property. Disruption is minimal as the material is injected from outside.

New installation regulations may require additional ventilation to be fitted as part of a cavity wall install.

*Based on a gas heated, detached property.

Check your wall type

TIP: If you're unsure whether you have cavity walls, check the brick pattern: The brick pattern will show all the long side of the bricks (see below for example)

If your house was built after the 1920s it is likely to have cavity walls. Older houses are more likely to have solid walls. 

If you can see the brickwork on the outside of the house, look at the pattern of the bricks. If your home has cavity walls, the bricks will usually have a regular pattern like this:


If your home has solid walls, the bricks will have an alternating pattern like this: 

Solid walls need external or internal wall insulation, more information can be found here


How much could you save?

England, Scotland and Wales

 DetachedSemi-detachedMid terraceBungalowFlat            

Fuel bill savings per year






Typical installation cost (if no grant applies) 






Payback time

                               5 years or less

Carbon dioxide savings (kgCO2/year)

1,040 kg

620 kg

380 kg

420 kg

290 kg

Is your home suitable?

Your home is suitable if:

  • Your property was built between 1920 – 1990 - as it’s likely to have uninsulated cavity walls.
  • Your walls have a cavity of at least 50mm wide, and is clear of rubble (installers will check this upon survey).
  • The brickwork of your property is in good condition. 

Note: If you are renting you will need your landlord’s permission before any work can be undertaken. 

Grants & Subsidies

Subject to your property and circumstances, there can be grants available to help towards the cost of installing cavity wall insulation. Note that extraction of old cavity wall insulation is unlikely to be funded.

For more information, head to our Financial Support page or contact Action Surrey on 0800 783 2503 or email 

Alternatively, fill out our enquiry form online and one of ourteam will be in touch.

Enquire now

* All figures are taken from the Energy Saving Trust April 2022.
**Average unsubsidised professional installation costs, although these will vary. Figures are based on fuel prices as of April 2022.