Cavity Wall Insulation Cost

When Britain is cold, it’s really cold. As a nation, we spend billions of pounds heating our homes every year.

The government has spent the last decade and more encouraging homeowners and tenants to install cavity wall insulation to cut those bills and reduce the amount of harmful greenhouse gases escaping into the atmosphere.

The good news is that the average cost of cavity wall insulation is relatively low compared to other home improvements.

A full installation can cost as little as £280 to £770, and your investment can be paid back in as little as three to six years through lower energy bills.

How Much Does Cavity Wall Insulation Cost?

Different sizes and types of property need different amounts of labour and insulating material, and the price also varies depending on where in the country you live.

As a guide, here’s the average cavity wall insulation price by property type:

Because most installers quote per property rather than per square metre, there isn’t one fixed cavity wall insulation cost per m2.

However, working from the figures above and typical wall areas for each property type, cavity wall insulation usually works out at roughly £4 to £12 per m², with most average-sized homes landing somewhere around £5 to £8 per m².

That makes it considerably cheaper per square metre than solid or external wall insulation.

How Much Does Cavity Wall Insulation Save On Utility Bills?

Up to 35% of the heat lost from your property escapes through your walls, so how much would you actually save by installing cavity wall insulation?

According to the Energy Saving Trust, likely annual energy bill savings by property type look like this:

What Is Cavity Wall Insulation?

Most homes built in the UK from the 1920s onwards were constructed using cavity walls: an outer “leaf” made of brick, and an inner wall made of either brick or concrete block, with a gap (the cavity) between them.

If your home falls into this category, older properties in particular can see a big jump in energy efficiency once that gap is filled.

An installer will typically recommend cavity wall insulation for your home if:

• there is no insulation currently present at your property;
• there is at least 5cm between your outer leaf and inner wall, with no rubble or other obstructive material between them;
• your property, particularly the brickwork or masonry, is in good condition;
• your property isn’t often subjected to intense, heavy, or driving rain;
• you don’t live in an area at risk of flooding.

For these types of home, your installer will typically recommend mineral wool or polystyrene beads.

For homes with very narrow or uneven cavities, your installer may recommend polyurethane foam instead, though this will usually cost more.

Installers may also suggest polyurethane foam if you live in an area prone to flooding or your walls are heavily exposed to the elements.

For semi-detached and terraced properties, your installer will fit a cavity barrier between your home and your neighbours’ homes.

For a flat, you’ll need to speak to the residents of the surrounding flats to insulate the whole building.

Cavity Wall Insulation Pros And Cons

There are some disadvantages to cavity wall insulation, but most experts, including those at the Energy Saving Trust, agree the advantages outweigh them in most cases.

Pros

Helps keep your home warm: Nearly 60% of what you spend on your utility bill goes on your boiler. Cavity wall insulation works a bit like the gas between two glazing panels.

It bounces much of the heat generated by your boiler and radiators back into your home.

Quick and easy to install: a skilled insulation fitter can often complete the whole job in as little as two hours, even on larger properties.

All the work is done from the outside, so there’s no need for disruption inside your home.

Reduces outside noise: the level of sound you hear from outside your home is often noticeably reduced once cavity wall insulation is installed.

Cons

Moisture: if your home already has issues with damp, get this sorted before considering cavity wall insulation. Insulation intentionally changes how air moves within your walls to keep heat in, and this can make existing damp worse.

It’s always worth asking your fitter to thoroughly check for damp before installation.

Potential visual damage to your exterior: depending on the skill of your fitter, a poor installation may leave scar marks on your exterior walls, which will likely need repainting to fully hide.

Wall tie damage: a cavity wall is held together by metal “wall ties.” Depending on the material used to fill your cavities, your wall ties may be at risk of rusting.

Frequently Asked Questions

How much does cavity wall insulation cost in the UK?

Cavity wall insulation cost in the UK typically ranges from £280 for a two-bed flat up to £770 for a four-bed detached house, including materials and labour. The exact cavity wall insulation price depends on your property’s size, type, and location.

How much does cavity wall insulation cost for a 3-bed semi?

A three-bed semi typically costs between £425 and £525 for a full cavity wall insulation installation, based on current UK average pricing.

Is cavity wall insulation worth the cost?

For most homes, yes. Since up to 35% of heat loss happens through your walls, cavity wall insulation can pay for itself within three to six years through lower energy bills, and many installations are eligible for free or subsidised funding.

How much can cavity wall insulation save on energy bills?

According to Energy Saving Trust estimates, annual savings range from around £50-£90 for a two-bed flat up to £175-£275 for a four-bed detached home, with a typical three-bed semi saving roughly £115-£185 a year.

How much does it cost to remove cavity wall insulation?

Removing cavity wall insulation is usually more expensive than installing it, since the material has to be carefully extracted from the cavity and the exterior brickwork often needs repairing and redecorating afterwards.

Are there grants to cover the cost of cavity wall insulation?

Yes. The Energy Company Obligation (ECO) scheme, currently in its ECO4 phase, funds free or heavily subsidised cavity wall insulation for eligible households, typically based on the benefits you receive, your property’s EPC rating, and your local authority area. See our cavity wall insulation grants guide for full eligibility criteria.