Did you know that around one-third of the heat loss from most homes is through the walls? By insulating your walls with cavity wall insulation, you can benefit from saving up to £485* per year on your energy bills, help to reduce your carbon footprint and keep your home warmer in the winter months and cooler in the summer.

We understand just how worrying those ever-increasing energy bills can be. That’s why we’ve put together this cavity wall insulation guide for householders, to explain what cavity walls are, help you understand whether your home is suitable for cavity wall insulation and what to look out for when choosing an installer.

The energy performance rating of your home

If you have recently purchased a new home or just sold one, you will know just how important the energy rating of your property is, with many people having access to the Energy Performance Certificate (EPC).

Energy Performance Certificates are a rating scheme to summarise the energy efficiency of buildings. Your home is given a rating between A – G. The EPC will also include recommendations on the most cost-effective ways to improve your home’s energy rating.

Cavity wall insulation is one of a number of insulation measures, that can improve the energy efficiency rating of your home and thereafter help improve the rating on your EPC.

Cavity wall insulation guide: What is a cavity wall?

The external wall of a house is constructed of two masonry (brick or block) walls, with a cavity (gap) of at least 40mm between. Cavity widths do vary depending on the build type of your home.

Houses built in the last 20 years are classed as ‘new build’ homes and will have already been insulated and meet the latest building regulation standards.

Cavity wall insulation guide: How can I tell my home has cavity walls?

If your home was built after the 1920s, it is likely to have cavity walls. Older houses (pre-1920) are more likely to have solid walls, with no cavities.

If you are unsure of the age of your home, then there is a simple way you can tell whether your home has cavity walls or a solid wall, by looking at the brick pattern. You can also find more information  by reading our comprehensive guide to how to find out if your home has cavity insulation

If your home has cavity walls, the bricks will all look the same size, like in the picture below:

Cavity wall insulation brick pattern

If your walls are solid, every other brick will probably be placed end-on and therefore not be suitable for cavity wall insulation, like this:

Solid wall brick pattern

Cavity wall insulation guide: Is my home suitable for cavity wall insulation?

An installer should carry out a thorough survey of your home and will be able to advise if cavity wall insulation is right for you.

• Check that your brickwork is in good condition
• That there is no existing dampness, mould, or condensation in your home
• That there is no existing insulation in your cavity walls by using a borescope
• There should be access to all areas of your home if possible, as cavity wall insulation is most effective when all walls can be insulated.  Access requirements and solutions for things like conservatories can be discussed with the installer.

Cavity wall insulation guide: How is cavity wall insulation installed?

Retrofit cavity wall insulation is injected with insulating material by drilling holes through the mortar joint of the external leaf. The drill holes are 22-26mm in diameter, dependent on the material used. The holes are then made good after injection. Each hole is injected in turn.

Installers commonly use a bonded bead product now, which is a system of cavity wall insulation that has been tested, assessed, and approved by the British Board of Agreement (BBA) and KIWA.

Cavity wall insulation guide: How long does it take to install cavity wall insulation?

Cavity wall insulation can be completed within 2 to 4 hours. However, this will depend on the size of the house and access around the property.

An installer will carry out a survey on your property to check suitability and will inform you of the time it will take to complete the installation.

Quality assurance: peace of mind

If you are looking to go ahead with cavity wall insulation, check the installer is Trustmark registered and for peace of mind, remember you will receive a 25-year industry-backed IAA (The Installation Assurance Authority) guarantee.

Trustmark registered

When you engage with a TrustMark registered business in relation to the installation of energy efficiency measures, you can have the confidence that the work is delivered to improved, recognised specifications.

Government-backed energy efficiency measure

The Government has backed cavity wall insulation as an effective energy efficiency measure for many years, which should offer you reassurance. As a result, cavity wall insulation has been included as a primary measure in several government schemes.

IAA guarantee 

Peace of mind with a 25-year industry backed Installation Assurance Authority (IAA) guarantee. The IAA is an independent body that provides a guarantee for cavity wall insulation fitted by registered installers in the UK.

Free insulation grants

Grant funding for those in receipt of benefits

If you are a low-income household in receipt of certain means-tested benefits and credits, and either a private homeowner or private tenant, living in a poorly insulated home with a low EPC rating, you may qualify for funding through the Energy Company Obligation.

The Energy Company Obligation is an obligation placed by the Government on to the energy companies, to provide funding for qualifying households, for energy-saving improvements.

Free home insulation for Council Tax Bands A to D

If you live in a home that falls into Council Tax Bands A to D, you may qualify for fully funded cavity insulation, as well as loft insulation, through the Connected for Warmth energy efficiency scheme.

New ventilation requirements

New Government driven standards, that came into effect from the 1st of July 2021, mean that householders who sign up to energy efficiency measures, for example cavity wall insulation through the Energy Company Obligation (ECO) scheme, will benefit from a new requirement to install additional ventilation in their homes, where required.

Effective ventilation helps keep your home energy-efficient, safe, and healthy as it helps to control the air flow.

You can find out more about new ventilation requirements and cavity wall insulation here.

Are you ready to beat those increasing energy bills by insulating your home?

Don’t forget, by ensuring your home is adequately insulated, you can benefit from:

• Savings on your energy bills
• Warmer home in the winter, cooler in the summer
• Helps to reduce your carbon footprint, playing your part in helping the environment
• Increases the value of your property
• Improves the Energy performance rating of your home
• Helps to reduce your carbon footprint

“We have to do our bit for future generations”

These are the words, Neil. Neil and Karen, a couple from Somerset, recently had cavity wall and loft insulation installed, which was funded through the Energy Company Obligation scheme and installed by Dyson Energy Services. They were keen to tell their story in the hope that it encouraged others to benefit from energy-saving insulation too.
Read their story.

*According to the Energy Saving Trust (EST):  Estimates based on a gas-heated detached home.  Figures based on fuel prices January 2024.