Can I have cavity wall insulation?

February 14, 2017
Can you get cavity wall

About a third of all the heat lost in an uninsulated home escapes through the walls.

Heat will always flow from a warm area to a cold one. In winter, the colder it is outside, the faster heat from your home will escape into the surrounding air.

In general, houses built from the 1990s onwards have wall insulation to keep the heat in, but if your house is older than that it may not have any wall insulation. If this is the case then you may be heating the outside air, instead of just heating your home. Most types of wall can be insulated in one way or another. If you have a typical house with cavity walls, you could save up to £155 per year in heating bills just from insulating the walls.

The first thing you need to find out is what sort of walls you have.

Cavity and solid walls

  • A cavity wall is made up of two walls with a gap in between, known as the cavity; the outer leaf is usually made of brick, and the inner layer of brick or concrete block.
  • A solid wall has no cavity; each wall is a single solid wall, usually made of brick or stone.

Working out your wall type

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:

If the brickwork has been covered, you can also tell by measuring the width of the wall. Examine a window or door on one of your external walls. If a brick 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.

Non-standard wall types

If your house is a steel-frame or timber-framed building, or is made from pre-fabricated concrete different rules apply for insulation.

Generally these houses don't have a cavity to fill, but it may be possible to insulate them in the same way as a solid wall. However, you may need a specialist company to insulate a non-standard wall. For further advice or to find an installer who can help you, contact the National Insulation Association.

Cavity wall insulation

Cavity wall insulation fills gaps often found between external walls in homes built after 1920, keeping the warmth in to save energy. It can also help reduce condensation inside the house if this is a problem stemming from your external walls.

England, Scotland and Wales


Semi detached

Mid terrace



Fuel bill savings (£/year)






Typical installation cost






Payback time

4 Years or fewer

Carbon dioxide savings (kgCO2/year)

1, 200 kg

660 kg

440 kg

450 kg

370 kg

These are estimated figures based on insulating a gas-heated home. The average installed cost is unsubsidised. Figures are based on fuel prices as of March 2016.

Northern Ireland

Fuel bill savings (£/year) £235 £135 £90 £95 £75
Typical installation cost £720 £475 £370 £430 £330
Payback time 5 Years or fewer
Carbon dioxide savings (kgCO2/year) 1, 400 kg 810 kg 540 kg 550 kg 440 kg

These are estimated figures based on insulating an oil-heated home. The average installed cost is unsubsidised. Figures are based on fuel rpcies as of March 2016.

Is cavity wall insulation suitable for your home?

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

  • 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.
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