Cavity Wall Insulation: Everything You Need To Know


How Does Cavity Wall Insulation Work?

Air acts as a natural insulator – in other words, heat does not travel through air very easily. Most people know that the best way to keep your body warm is to wear several layers of clothing. This is because the layers trap air in between them and keep it still. CWI works in a very similar way. The wool-like material used to insulate your home traps air in between its fibres to create an ‘air matrix’. This is why CWI is much more effective at retaining heat than empty cavity walls.

How Do I Know If I Have Cavity Walls?

Before you decide to have your cavity walls insulated, you need to know whether or not your property has them. One clue is the age of your house. People started to build houses with empty cavities roughly around the 1920s. This was standard practice up until the mid-1980s, when building regulations stated that all new houses had to be built with insulation material already inside the walls. So if your house was built between 1920 and 1980 there is a good chance that you have empty cavity walls.

If you’re not sure about the age of your house, another simple way to tell is by looking at the brick pattern of you outside walls. In a typical cavity wall, all of the bricks will look the same K Render Manchester with the long side of the brick visible on the outside. With solid walls the bricks will be in an alternating long-short pattern.

What if your walls are rendered or the brickwork isn’t visible for some other reason? In that case, take a look at the thickness of your exterior walls. You can do this easily by looking at a doorway or a window. If it is more than 260mm thick, chances are you have cavity walls.

Finally, how do you know if a previous owner hasn’t already had the CWI installed? You can actually tell by taking a close look at your external walls. If the cavities have already been insulated, you will notice a few small drill holes in the mortar between the bricks – they will have been filled and won’t be very obvious, but look closely and you will see them. This is where the installers will have blown the insulation into the walls.

Still not sure? A trained energy surveyor can inspect your walls for free and let you know if they are suitable.

If it turns out you have solid walls, or for some other reason your house is not suitable for CWI, then you may want to consider solid wall insulation instead.

Grants for Cavity Wall Insulation

Paying for your own cavity wall insulation can potentially cost several hundred pounds. The good news is that at the time of writing this article, you can have it done for free – your energy provider will cover all of the cost. There is no catch and everyone qualifies for a grant thanks to the governments CERT initiative.


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