Cavity wall insulation

Watch our video guide to cavity wall insulation.

In most houses built after the 1920s, the external walls are made of two layers with a small air gap or 'cavity' between them. If your home has unfilled cavity walls, a considerable slice of your energy bills will be spent heating the air outside. If you don't have cavity walls find out about the insulation options available for solid walls.

Typical brick formation for cavity walls

How cavity wall insulation works

Filling the gap between the two walls of a house with an insulating material massively decreases the amount of heat which escapes through the walls. It will help create a more even temperature in your home, help prevent condensation on the walls and ceilings and can also reduce the amount of heat building up inside your home during summer hot spells.

The savings

Around a third of all the heat lost in an un-insulated home is lost through the walls. If you have cavity walls, insulating them will make a great difference, and it could save you around £120 a year on your fuel bills.

The following table gives approximate costs, savings and paybacks for cavity wall insulation however the typical cost provided does not include any financial support or grants. Financial help may be available if you're planning to make energy saving improvements to your home.

The Government, energy suppliers and local authorities all provide grants or offers to help you implement energy saving measures in your home. For more information or to search for energy saving grants and offers, please click here.

How the savings add up

If all the houses in the UK with unfilled cavity walls had them filled, the energy saved could heat a staggering one million homes each year.

Cavity wall insulation can pay for itself within 4 years

How it is installed

Cavity wall insulation is quick, clean and relatively inexpensive to install. It's injected into the cavity from the outside taking between two and three hours in a three bedroom semi-detached house. It usually costs around £500, and with the savings you make on your heating bills, it can pay for itself in around four years.

See how cavity wall insulation is installed

Find out if you are entitled to a grant or offer to help you pay for the installation

What to do next

If you have other questions about cavity wall insulation why not visit our FAQ section. If you still have other questions why not call your local Energy Saving Trust advice centre on 0800 512 012 for free, impartial advice on saving energy in your home.

Find a registered installer by visiting the Cavity Insulation Guarantee Agency (CIGA) website or the National Insulation Association (NIA) website

• Find Energy Saving Recommended cavity wall insulation
• Savings assumptions

Sign up for regular email updates to help you save money and energy