What is cavity wall insulation?

It is important to get your cavity wall insulated, we will explain what cavity walls insulation is and how it works in this Blog.

About a third of all the heat lost in an uninsulated home escapes through the walls. By properly insulating cavity walls, you will save energy and cut costs off your heating bill.

In general, houses built from the 1990's on-wards have wall insulation to keep the heat in, but if your house is older than that, it may not have any wall insulation at all.

Houses in the UK mostly have either solid walls or cavity walls:

 If your house was built after the 1920's, it is likely to have cavity walls. A cavity wall is made up of two walls with a gap in between, known as the cavity; the outer leaf is usually made of brick, and the inner layer of brick or concrete block. Pre-1920 older houses are more likely to have solid walls. A solid wall has no cavity; each wall is a single solid wall, usually made of brick or stone.

Working out your wall type

The first thing you need to find out is what sort of walls you have. If you can see the brickwork on the outside of the house, look at the pattern of the bricks.

If your home has cavity walls, the bricks will usually have an even pattern with all the bricks laid length ways. Or you can ask a cavity wall company to come inspect your walls. They can drill into the wall and check there is a cavity is there and that it is not too narrow or check for debris in the cavity (which can be removed)

If your home has solid walls, the bricks will have an alternating pattern, with some bricks laid across the wall so you can see the smaller ends from the outside.

f the brickwork has been covered, you can also tell by measuring the width of the wall. Examine a window or door on one of your external walls.

If a brick wall is more than 260mm thick then it probably has a cavity.A narrower wall is probably solid. 150mm Stone walls may be thicker still but are usually solid 500mm+

Some houses have a different type of wall structure altogether. If your house is a steel-frame or timber-framed building, or is made from pre-fabricated concrete, then you will need to ask a specialist insulation installer to advise you.

Cavity wall insulation explained

Many cavity walls can be insulated by injecting insulation material into the cavity from the outside. A specialist company will drill holes in the outside walls, inject insulation through the holes and then seal them with cement. The insulation materials is usually either mineral wool or polystyrene beads, but polyurethane foam may sometimes be used instead.

To insulate your cavity walls, the installer drills small holes around 22mm in size at intervals of around 1m in the outside wall of your home. The installer then blows insulation into the cavity using special equipment. Once all the insulation is in, the installer fills the holes in the brickwork so you'll barely notice them.

Filling cavity walls is not a job you can do yourself, you will need to employ a registered installer. A professional can do the job in around two hours for an average house with easily accessible walls. It shouldn’t make any mess.

The Benefits of Insulation

6 million homes in Britain have now had cavity wall insulation installed, and it’s easy to see why – it’s the smart way to save money.

The Government regards cavity wall insulation as one of the most effective energy savings measures that most people can carry out on their homes and apart from saving money it’s a major contributor to reducing emissions of carbon dioxide, the main greenhouse gas.

What’s more, millions of homeowners will tell you that insulation is quick, simple and mess free to install, and cavity wall insulation is a safe reliable system that has been used for many years and has a proven track record. In the unlikely event of a problem occurring the CIGA 25 year Guarantee ensures that access to specialist technical help and assistance is available to provide complete peace of mind.

External walls account for 35% of heat loss from the average house, and studies suggest that every square metre of Cavity Wall Insulation will save more than a tonne  of Carbon Dioxide over the average life of the building. For a semi detached house with an external wall area of 80m2, this equates to savings of 80 tonnes or more.

With an uninsulated cavity heat can easily escape meaning it requires more fuel to maintain a comfortable temperature.

The insulation present in a filled cavity reduces this heat loss, making the house warmer or reducing the amount of fuel required to maintain a comfortable temperature.

Around 5 million homes still have empty cavities that could have CWI installed, allowing the occupants to enjoy a warmer and cheaper to heat house. Various Grants and schemes are available to help with the cost, so there really is no reason not to benefit from a warmer and cheaper to heat home by contacting a CIGA Registered installer.

Cavity wall insulation


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