Insulate your cavity walls for free and save up to £275 a year

More than a third of all heat lost in uninsulated homes escapes through external walls, which is tough on the environment and your pocket. Heat flows from warmer to colder temperatures and in the winter, the colder it is, the more quickly heat will escape from your home if the walls have a cavity that’s not insulated.

Under the Energy Companies Obligation (ECO) scheme, you could be eligible for free cavity wall insulation, as well as free loft insulation.

What are the benefits of cavity wall insulation?

  • Reduces heat loss through your walls
  • If you qualify, it could be free, so there's no cost to offset against savings
  • Could reduce your energy bills
  • Keeps your home warmer in winter
Workman carrying out cavity wall insulation

How much money can cavity wall insulation save?

Cavity wall insulation is a great way to save money. According to the Energy Saving Trust, having your cavity walls insulated to the correct specifications, can save you up to £250* per year.

Cavity wall insulation

By installing cavity wall insulation, you could save up to 1,100kg* of carbon dioxide emissions each year.

Savings will vary from property to property.

All cavity wall insulation comes with an independent 25 year guarantee from CIGA (Cavity Insulation Guarantee Agency) to provide complete peace of mind.

Source: *Energy Saving Trust 2018. These are estimated figures based on insulating a gas-heated, detached house. Figures are based on fuel prices as at April 2018.

What is a cavity wall and why do I need to insulate it?

A cavity wall refers to the type of wall where the property is built from an inner and outer wall. The gap between the two walls is the cavity which was designed in the 1920’s to stop damp penetrating homes. The outer wall is typically blockwork with render or brickwork. The inner wall is usually concrete block or breeze block with an internal plaster finish.

Filling that gap with insulating material can be very effective in reducing heat loss from your home and cutting the cost of your energy bills. Savings of as much as £250 per year for the average detached home are possible, according to the Energy Savings Trust.

How do I know if I have cavity walls?

Most homes built in the past 100 years were built with two layers of wall, leaving a small space or ‘cavity’ between the two layers. If your home was built before 1920 the walls are more likely to be solid without a cavity, but if it was built after 1920 and before 1990, it most likely will have cavity walls. Most houses built after 1990 have wall insulation already installed at the point of building the house to keep the heat in.

To be certain if your home has cavity walls, there are a few visual clues you can use:

  • Measuring the thickness of the walls
    Measure the wall next to a window or a door. If the wall is thicker than 26cm, it’s likely to have a cavity.
  • Checking the pattern of the brickwork
    If you can see the brickwork then it’s also worth checking the pattern of the bricks. If the bricks are laid in a familiar oblong end-to-end pattern like the photo on the left below, then it’s likely to have a cavity. If you can see some of the bricks have been laid with both the square and the oblong end facing like the photo on the right below, then it probably won’t and you will have a solid wall.
Cavity wall
Cavity wall
Solid wall
Solid wall

Of course if your wall is made entirely of stone, so a solid wall, it won’t have a cavity.

How do I know if my cavity wall is insulated?

There are a few ways you can find out if your walls are insulated but if you’re unsure or you can’t find out, we recommend that you assume they’re not.

To find out:

  • Check your property’s EPC certificate or search for it on Landmark
  • Check your property’s documents and see if you have a certificate, such as aCIGA guarantee certificate

How is cavity wall insulation installed?

Even if you’re a dab hand at DIY, it's not a job that anyone can do and you'll need an expert to complete this for you. However, it’s not that big a job so can be fairly quick and straightforward to complete.

Your installer will drill some small holes in the external wall and inject the insulating material into the cavity, which stops the warmth passing through the walls. In most cases the work isn't disruptive and, depending on the property, may only take a couple of hours to complete. The holes are filled once the cavity has been filled.

Workman installing cavity wall insulation

What is cavity wall insulation made out of?

The two most common cavity wall insulation materials used by our professional installers are mineral wool and Polypearl polystyrene beads. They are blown into the cavity wall using high pressure compressed air.

Mineral Wool - this is made from recycled glass that is spun into a fibre-like structure. It’s rigorously tested and used nationwide by approved installers of cavity wall insulation. As well as being able to install it in any weather, it also has a low environmental impact since it uses recycled glass, plus a 25 year guarantee.

Polystyrene Beads – They consist of small, white and grey bead like material and will be more likely to be used by our installers for spaces that the mineral wool may not be suitable for, such as partially filled cavity wall spaces or narrow wall cavities. Both of these cavity wall insulating materials are covered by British Board of Agrement (BBA) certificates.

Does cavity wall insulation cause damp?

There's a common misconception that cavity wall insulation causes damp since the space being filled was designed to prevent damp. But according to a Which? report this is very rare and could only occur in properties as a result of cavity wall insulation if there’s a combination of the following:

  • your home being exposed to severe levels of wind-driven rain;
  • your home being located in an unsheltered position unprotected by trees or other buildings;
  • the external walls are poorly built or maintained with, for example, cracks in the brickwork or rendering.
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