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Cavity wall insulation

Cavity wall insulation costs and savings

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Cavity wall insulation costs and savings

Does your home have cavity walls? Find out how much it costs to get cavity walls insulated, and how much you could save on your heating bills.

Around than a third of all heat lost from an uninsulated home escapes through the walls. So it shouldn’t be a surprise that installing cavity-wall insulation is often one of the most cost-effective measures you can take to save energy in your home.

Cavity-wall insulation costs and savings

As you'll see in the table below, you could save up to £225 a year by insulating cavity walls.

Cavity wall insulation
Type of property Installation cost Savings per year CO2 savings per year (kg)
Detached house (four bedrooms) £725 £245 1,080
Semi-detached house (three bedrooms) £475 £140 640
Mid-terrace house (three bedrooms) £370 £90 400
Detached bungalow (two bedrooms) £430 £100 430
Mid-floor flat (two bedrooms) £330 £70 300

Table notes: figures based on a typical gas-heated home in England, Scotland and Wales. All data obtained from the Energy Saving Trust (EST).

All cavity wall insulation installations take fewer than 5 years to pay for themselves through energy efficiency savings, according to the Energy Saving Trust.

How wall insulation works

Wall insulation acts as a blanket that prevents heat from escaping through the walls, and uniformly spreads heat around the home. It can also help to stop your home getting too hot in summer.

Type of wall

The type of wall insulation you’ll need depends on whether your home has cavity or solid walls. If your home was built from 1920 onwards, it’s likely to have cavity walls. 

If you have solid wall insulation, see our separate guide for information on solid wall insulation

Both types should be installed by a professional installer. You can find a local, trustworthy installer on Which? Trusted traders.

Cavity-wall insulation

Cavity-wall insulation is injected through the outer wall of your home into the space between the inner and outer leaves of brickwork that make up cavity walls.

It’s cost effective – it costs between £330 and £720 depending on the size of your home. Cavity-wall insulation should pay for itself in four years or less through the savings you’ll make on your heating bills.

When Which? investigated cavity-wall insulation sales practices in 2011, we uncovered some concerns about assessments, price differences and poor advice. You can watch our undercover video by clicking cavity-wall insulation damp problems

To make sure you’re paying the right price for insulation and getting the right advice, see cavity-wall insulation installation.

Free cavity-wall insulation

People with cavity wall insulation that is defined as ‘hard to treat’ can benefit from subsidy under the Energy Company Obligation.

‘Hard to treat’ means walls that are not straightforward to fill because, for example, they need remedial work or have been already partially filled.

For more information on which grants are available and how to apply, see our guide on insulation grants.    

Insulation and home energy-efficiency ratings

An Energy Performance Certificate (EPC) is needed when you want to sell your house. A home’s EPC shows an overall energy-efficiency rating for your home from A-G. ‘A’ represents the most energy efficient properties and ‘G’ the worst. The EPC also contains advice on how to cut carbon emissions and fuel bills by making home improvements.

Fitting insulation is an effective way of raising your home’s energy-efficiency rating. If you don't have insulation installed, the EPC will recommend the type and level of insulation required for maximum efficiency.

Loft, roof and floor insulation

If you already have wall insulation, or want to make additional energy-saving improvements to help make your home nice and cosy and boost its EPC rating, there are a number of things you can do. 

These range from quick, easy fixes to stop draughts – such as using a draught excluder on your front door. For more on advice, see our expert guide to draught proofing. You could also consider installing loft, roof or floor insulation

Other home energy-efficiency measures include fitting a jacket to your boiler and installing double glazing.

Want to know what double glazing customers really think of the companies that installed their new windows? Read our double glazing company reviews.