Cavity Wall Insulation

What is it:

Cavity walls have two walls with a gap or ‘cavity’ between them. If your home was built after the 1920s, it’s likely to have cavity wall

Cavity walls can be insulated by injecting insulation into the cavity from the outside through drill holes in the outside walls. Insulation is usually mineral wool or polystyrene beads, or polyurethane foam. The holes are filled after this process making them hard to see.

This insulation helps reduce the heat lost through your walls.

Cavity wall insulation

What are the benefits?

Save money on your bill

Insulating the walls of your property means less heat can escape, lowering the cost of heating

Reduce your carbon footprint

Using less energy to heat your property means less CO2 is released into the atmosphere, reducing your impact on climate change

Increase your property value

Increasing the energy efficiency of your property increases the value of the property and makes it more appealing to buyers and renters

Improve living conditions

A well insulated property will be easier to heat to a comfortable temperature. It will also help keep the property cooler in summer

Brick wall

What properties is it suitable for? 

Cavity walls can be identified by their brick pattern which is usually an even pattern with all the bricks laid lengthways.

If the brickwork has been covered, you can measure the thickness of the wall. Anything over 260mm is likely a cavity wall

Your home will be suitable for standard cavity wall insulation if it meets the following criteria:

  • Its external walls are unfilled cavity walls.
  • Your cavity is at least 50mm wide, and is clear of rubble.
  • The masonry or brickwork of your property is in good condition.
  • The walls are not exposed to driving rain.
  • Your house is not at risk of flooding.

You will need an installer to carry out a survey to check that your house is suitable. If so, they will then be able to insulate your walls using mineral wool or polystyrene beads.

Click here to find out what insulation measures would be suitable for your property.

Typical cost

The cost depends on the size of your property and the walls to be insulated, but a general rule of thumb is that it will cost around £200 per each two-storey wall.

A mid-terraced house with only two external walls could cost under £400, while a detached property may be £800 or more.

Available funding

Funding is available for owner-occupiers and privately let properties where occupiers meet certain eligibility criteria. Click the below tiles to find out if you’re eligible for funding.

How to find an installer

When choosing an installer, make sure they are Trust Mark accredited. This is a government backed accreditation that demonstrates installers are reliable and professional. This information can usually be found on an installers website. Click here to visit the TrustMark website to find an insulation installer near you.