Cavity Wall Insulation

cavity wall insulation

If your house was built after the 1920s, it is likely to have cavity walls. Older houses are more likely to have solid walls.

If you can see the brickwork on the outside of the house, look at the pattern of the bricks. If your home has cavity walls, the bricks will usually have a regular pattern, if your home has solid walls, the bricks will have an alternating pattern.

cavity wall brick pattern

Cavity Wall Brick Pattern

solid wall brick pattern

Solid Wall Brick Pattern

If the brickwork has been covered, you can also tell by measuring the width of the wall. If you look at the thickness of an external wall where a window or door is, if the wall is more than 260mm thick then it probably has a cavity; a narrower wall is probably solid. Stone walls may be thicker still but are usually solid.

How much you can save?

Below is a table of Cavity Wall Insulation saving figures for England, Scotland and Wales.

 DetachedSemi-detachedMid-terraceBungalowFlat
Fuel bill savings (£/year)£275£160£105£110£90
Typical installation cost£720£475£370£430£330
Payback time5 years or fewer5 years or fewer5 years or fewer5 years or fewer5 years or fewer
Carbon dioxide savings (kgC02/year)1,100 kg650 kg430 kg450 kg360 kg

These are estimated figures based on insulating a gas-heated home provided by the Energy Saving Trust. The average installed cost is unsubsidised.

Is cavity wall insulation suitable for your home?

Your home will usually be suitable for cavity wall insulation if it meets these criterias:

  • Its external walls are unfilled cavity walls.
  • Your cavity is at least 50mm wide.
  • The masonry or brickwork of your property is in good condition.
  • It is more than 10 years old (most newer houses will have insulation already).
  • The walls are not exposed to driving rain – although there are products available for this situation.

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