According to the Energy Saving Trust, an un-insulated home loses around a third of its heat through the walls. So it comes as no surprise that there is a huge market for cavity wall insulation for all homes that are applicable.

If you live in a house built after 1920, there’s a good chance you have cavity walls. These are external walls made up of two layers with a small gap or ‘cavity’ between them. So cavity wall insulation means filling that cavity with insulating material to prevent heat escaping from your home.

Just like loft insulation, cavity wall insulation is an effective way of cutting the cost of your heating bills and reducing your CO2 emissions by keeping the heat your home generates inside rather than letting it easily escape.

In fact, the Energy Saving Trust claims you can save up to £115 a year by having cavity wall insulation. This figure is based on insulating a gas-heated, semi-detached home with three bedrooms.

You can even get a grant to help towards paying for the insulation as part of the Government’s Carbon Emissions Reduction Target (CERT). And you could even qualify for free cavity wall insulation.

In order to qualify for having cavity wall insulation you need to find out a few things first.

Do I have Cavity Walls?

Most importantly, find out if you have cavity walls, and if so are they already insulated? There are three checks you can do yourself to see if you have cavity walls.

Firstly, how old is your house? Cavity walls didn’t become a normality in construction of homes until the early 1930’s so any home built before 1932 is unlikely to have cavity walls and you may have to look into solid wall insulation or timber frame insulation. If the house was built between 1932 and 1982 then it’s highly likely you do have cavity walls. And it’s just about a certainty if your home was built post 1982.

The second think to check is the pattern of the bricks on your outside wall. There are three common styles – English bond, Flemish bond and Stretcher bond. Stretcher bond walls most likely to have cavity walls. This style is when all the bricks are laid horizontally.  You’ll be able to tell the difference as Flemish bond walls have bricks alternating between a full length brick and a half length brick and an English bond is when there are alternating rows of full and half length bricks. During these checks it’s also worth looking out for any damage to brickwork that could already be causing damp problems.

The third and final check you can do yourself is measuring the thickness of your outside wall. Cavity walls tend to be thicker than solid walls because they have the cavity gap between the internal and external brick. Measuring the thickness is easy – open your front door and measure from the outside face of the wall to the inside face of the wall. If it is less than 30cm/11.5 inches then it’s highly unlikely the walls are cavity walls. Anything over that measurement suggests you do have cavity walls.

Are my Cavity Walls Insulated?

If after these checks you think you do have cavity walls, you’ve now got to see if those cavities are insulated. If the house is less than ten years old there’s a good chance it will already have a block of insulation fitted in the cavity when the walls were initially put up. But you will have to check with your home documentation to see if there is any information from the original builder or a survey. There is a chance that an older house could have cavity wall insulation too, so again check your documentation.

Contact a professional

If you discover you have cavity walls but no insulation then your next move should be to contact a registered installer. There are no D.I.Y options with cavity wall installation; it has to be done by professionals.

To fill the cavity with insulation, the installer will drill small holes (approx 22mm in size) spaced between 1 and 1.5 metres apart. Tubing is then fitting into the wall through the holes and insulation material is blown into the cavity. The holes in the brick work are then covered up with colour-matching mortar.