Cavity Wall Insulation – How it Works and How you Can Get it Installed for Less

In most UK houses built after the 1920s, the external walls are made of 2 layers with a small air gap or cavity in between them. If your home has unfilled cavity walls, a considerable slice of your energy bills will be spent heating the air outside. In fact it is estimated that around 35% of the heat from your home is lost through the walls.

Filling the gap between the 2 walls of a house with an insulating material massively decreases the amount of heat (and money) that is escaping through your walls. This could save you between £130 and £160 a year on your fuel bills for an average house, according to the UK’s Energy Saving Trust, and pay back the cost of installation in under 2 years. It will also prevent around 1 tonne of CO2 emissions each year, so makes a significant contribution to fighting Climate Change. Plus having your cavity walls insulated will make your home more comfortable by evening out the temperature in your home, help reduce condensation, and also keep your home cooler in hot summer weather.

This is a job that is definitely best done by a professional, as it can be quite technically demanding and requires specialist equipment. However, despite paying a contractor, it can be done for little money. This is because the large UK gas and electricity companies heavily subsidise the cost of insulation through certain contractors, in order to reach their carbon reduction targets set by the government. Typically they pick up 30 to 70% of the bill, no matter what your income. The contractor will also take care of all the paperwork, so that you automatically get these subsidies. In addition, if you receive certain state benefits, the government will pick up the rest of the cost so you can get your home installed completely free. When you get a quote from a contractor, they will be able to tell you whether you qualify for these grants.

How is cavity wall insulation installed? The cavity wall is injected with insulating material by drilling small holes in the external wall through the mortar joints. The holes are generally around 2cm wide and are made good after the injection by the installer. The material injected is normally ‘mineral wool’ (fibres made from rock or glass), polystyrene beads or white foam. All materials have a similar insulation performance. The insulation normally takes about 2 hours to install, but the time does depend on the size of the house and other factors such as access.

How do you know if your house has cavity walls? Most houses built after the 1920’s have been built with cavity walls. An easy way to check is to look at the brickwork in your outside walls. If all the bricks are laid the same way, with just their sides showing (rather than their ends), then you have cavity walls. But you don’t need to make sure of this yourself. All good insulation contractors will offer you a free no-obligation insulation survey, when they can check for your and let you know what is possible.

All reputable cavity wall insulating contractors in the UK are members of the Cavity Wall Insulation Agency (CIGA) guarantee scheme. This scheme gives you a 25 year guarantee on your cavity wall insulation, so that you can be completely confident in the quality of the work. Plus you will be able to pass this guarantee on to any future purchaser of your house, which will help contribute to your house’s value.

If you are interested in installing cavity wall insulation, you should contact a reputable contractor to request a free no-obligation survey. You can do this through the site mentioned at the bottom of this article (go to the page about insulation), or else several contractors advertise on the Internet (if you type in ‘cavity wall insulation’ into Google)