Cavity Wall Insulation (All You Need to Know)

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Your home probably has cavity walls if it was built after the 1920s. There’s a good chance that those cavities are empty unless it was constructed within the last 20 years. It could be very cost-effective to fill them with wall insulation and save on your energy bills if that is the case.

Most homes lose heat through the walls so cavity insulation could save you up to £160 in heating bills1. According to the Energy Saving Trust website, it is estimated that cavity wall insulation can pay for itself in less than five years.

This is the unsubsidized cost of installation Cavity wall insulation These figures are estimated based on insulating a gas-heated home in England, Scotland, and Wales. The payback period may vary depending on when the insulation is installed, since the amount saved varies from winter to summer.

Introduction of Cavity Wall

Cavity walls are made up of two thin walls (usually bricks, called skins or leaves) separated by a gap (or cavity). The walls are usually held together with metal wall ties.Cavity walls can be made of concrete, brick, and mortar. The cavity is filled with either concrete or mortar, depending on the strength required. Advantages and disadvantages of cavity wall construction Cavity walls are considered to be stronger than standard masonry walls because they have a larger amount of reinforcement between the two outer skins. However, cavity walls can be more difficult to construct and may require additional reinforcement.

How To Tell If a Wall Has Cavities

Your home’s age is the first indication that there are cavities. Nevertheless, if you’re not sure how old a wall is, or suppose it was built around 1930, so it could be either a cavity wall or a solid wall, look at the exposed brickwork. The bricks in your home with cavity walls will all look the same size, similar to this: … but if the walls are solid, every other brick will have been placed end-on, similar to this:

You may be able to determine the thickness of your home’s outer walls if all the brickwork has been rendered or clad so there can be no visible bricks.It is also possible to check the doors and windows. Solid stone walls can also be thick, even if they are made of brick. Brick walls that are thicker than 10 inches are probably cavity walls.

What To Do If Your House Does Not Have Cavity Wall Insulation

Your home was likely built with insulated walls if it was built within the last 20 years. In case it wasn’t or if you want to make sure:

  • If you are unsure whether the wall is insulated or empty, have a registered installer drill you a small hole. You can then use a borescope to determine whether the wall is insulated.
  • You should consult the building control department of your local authority. This department has records if your walls are already insulated.

There are also a few signs to watch out for to prevent the need for a borescope examination:

  • The installers will insert the wall cavity insulation through 1-inch holes drilled at regular intervals. There will still be faint marks left, even though these will be filled in – but don’t confuse these with the marks left by the damp proof course injected in.
  • You may find cavity insulation spilling out of the wall at the top of your attic. It’s not a good sign! It is probably best to get a professional to clean this up and seal off the wall if you see this.

Is It Possible to Insulate a Home Without Brick Walls?

You probably don’t need to insulate stone walls because they’re likely solid, with no cavities. Alternative ideas can be found in our ultimate guide to solid wall insulation.

If you live in a timber-framed or steel-framed building, or if your home is constructed from prefabricated concrete, you won’t have cavity walls. However, you may be able to insulate them in another way. Contact the National Insulation Association to find a suitable installer in your area.

The contractor should not suggest injecting wall cavity insulation between the outer brick leaf and the inner frame of a timber-framed home since it can cause serious damage.