Cavity Wall Insulation Cost

When Britain is cold, it’s really cold. As a nation, we spend billions of pounds heating our homes and apartments every year. In an effort to cut down our household bills and to reduce the amount of harmful greenhouse gasses escaping into the atmosphere, the government have spent the last 10 years and more encouraging homeowners and tenants to install cavity wall insulation in their homes.

The good news is that it can cost as little as £280 to £770 for a full installation and your investment can be paid back in as little as three to six years. The even better news is, that for many Britons, you can have cavity wall insulation installed in your home (whether you’re a homeowner or a tenant) free of charge or at a heavily subsidised price.

In this article, the Compare Companies team looks at:

  • Cavity wall insulation installation costs
  • Cavity wall insulation energy bill savings
  • What cavity wall insulation actually is
  • The pros and cons of cavity wall insulation

Want to find out more about cavity wall insulation and whether you qualify for free or heavily-subsidised installation under the government ECO3 scheme? We connect homeowners and tenants across the UK with reputable and trusted cavity wall insulation professionals for the best advice and the very latest information. If you’re paying for your cavity wall insulation installation, we can even help you save up to 40% on your costs. Click here to fill in our no-obligation quote form and remember that our service is 100% free.

How much does cavity wall insultation cost?

Different sizes and types of property require different levels of labour and insulating material. The amount you pay will also vary depending on the part of the country you live in but you should look to budget the following:

Type of propertyInstallation cost
Four-bed detached£670-£770
Three bed semi£425-£525
Three bed mid-terrace£320-£420
Two-bed bungalow£380-£480
Two-bed mid-floor flat£280-£380

How much does cavity wall insultation save in utility bills?

Up to 35% of heat loss from your property is through your walls so how much would you save on your utility bills if you actually install cavity wall insulation? According to the Energy Saving Trust, the likely annual energy bill savings depending on the type of property you live in look like this:

Type of propertySavings Per Year
Four-bed detached£175-£275
Three bed semi£115-£185
Three bed mid-terrace£75-£115
Two-bed bungalow&85-£125
Two-bed mid-floor flat&50-£90

As you can see, you may be able to pay off your installation in full from those savings within three to six years depending on the size of your property and the price you pay for the installation.

What is cavity wall insulation?

Most homes built in the 1920s and later in the United Kingdom were constructed using cavity walls. What that means is that there’s an outer “leaf” which is made of brick and an inner wall which is made of either brick also or from concrete block. There is a gap between the outer leaf and the inner wall – that’s the cavity.

An installer will 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 and there is no rubble or other obstructive material between them
  • your property, particularly the brickwork or the masonry, is in good condition
  • your property is not often subjected to conditions of intense, heavy, or driving rain
  • you don’t live in an area at risk of flooding

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

Mineral wool, made from either melted rock or glass spun into high density fibre strands, is the most widely used type of insulating material. It’s generally considered to be both affordable and environmentally friendly. Polystyrene beads, on the other hand, are adhesively-bonded and more commonly used when the cavity between your walls is narrower than standard (for example, many conservatories are retro-fitted with beads for insulation).

For homes with very narrow cavities or where the cavities are uneven, your installer may recommend a polyurethane foam however this will be more expensive for you. Installers may direct you towards polyurethane foam insulation if you live in an area prone to flooding or your wall is exposed to the elements.

For semi-detached and terraced properties, your installer will fit a cavity barrier between your home and your neighbours’ homes. Likewise, for a flat, you will need to speak to the people living in the flats surrounding your property to insulate the whole of the building.

Cavity wall insulation pros and cons

There are some disadvantages to cavity walls however most experts, including those at the Energy Saving Trust, agree that the advantages outweigh them greatly in most cases.


Helps you keep your home warm

Did you know that nearly 60% of what you spend on your utility bill is spent on your boiler? Your boiler provides you with all the warmth and hot water you need but it comes at a big price every year for British households.

Cavity wall insulation works, in many ways, like the gas between two glazing panels in that it bounces much of the heat generated by your boiler and your radiator back into your home. And, as we’ve seen, according to Energy Saving Trust figures, cavity wall insulation can save you up to £275 on your annual energy bills.

Very quick and easy to install

Working with a skilled insulation fitter means that the whole job can be carried out in as little as two hours, even on larger properties. All the work is done from the outside meaning that there’s no need for disruption inside your home.

Outside noise

The level of the sound you hear from outside your home is often greatly reduced once you have cavity wall insulation installed and you’ll notice it immediately.



If your home already has issues with damp and you’re considering cavity wall insulation, you should get this sorted before anything else. Insulation intentionally affects the way that air moves in your walls to keep the heat in and this effect could actually make your damp worse. It’s always really important to ask your fitter prior to installation to thoroughly check for damp.

If cavity wall insulation is installed before sorting out any damp problem, the material used could actually act as a means of travel for the moisture to move from your outer brickwork to your inner walls. Excessive moisture in your home promotes the growth of mould and mould can be a very serious health threat particularly for the very young and very old.

Potential visual damage to your property’s exterior

Depending on the skill of your fitter, a poor installation may leave scar marks on your exterior walls. These scar marks will be visible and will likely require the painting of the side of your house which is affected by it to completely obscure the scar marks from view.

Wall tie damage

A cavity wall is held together by “wall ties” – they’re rods made from metal that hold each side of the wall in place and together. Depending on the substance used to fill your wall cavities, your wall ties may be at risk of rusting. In extreme cases, this may lead to the eventual collapse of the outer leaf of your cavity wall.

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