How to insulate your Home - Cavity Walls

Roughly a third of heat is lost through un-insulated walls.

Roughly a third of heat is lost through un-insulated walls, heat will always move from a warm area to a cold one and the colder it is outside the faster the heat in your home will escape into the surrounding air. Insulating a cavity wall will reduce your fuel bills considerably.

What type of walls do you have?

The majority of homes in the UK have one of two types of walls:

  • Cavity walls consist of two walls with a gap in between, referred to as the cavity; in order to insulate a cavity wall, the cavity should be filled. The outside is made up of brick and the inside is made up of brick or concrete blocks. If your home was built after 1920, you are likely to have cavity walls.
  • Solid walls are made up of one single solid wall usually made of brick or stone. If your home was built before 1920, you are likely to have solid walls – this means more energy is being used while your home tries to retain its heat. Find out more about solid walls.

Other types of walls

If your home is made up of steel or timber frames, or pre-fabricated concrete, you may not have a cavity wall to fill, but you may be able to insulate your walls in the same way a solid wall would be insulated. To insulate an other type of wall you may need a specialist company, for more information or to find an insulation installer contact the National Insulation Association.

To help find out what types of walls you have in your home, visit Energy Saving Trust’s Home Energy Check tool

How much could you save?

If you live in England, Scotland or Wales you could save the following on your fuel bills per year:

  • Detached house: £245
  • Semi-detached house:  £145
  • Mid terrace house: £90
  • Detached bungalow: £100
  • Flat: £70

These are estimated figures based on insulating a gas-heated home. The average installed cost is unsubsidised.

Source (of saving): Energy Saving Trust

Cavity wall suitability

If your walls meet the following criteria, they’re suitable for insulation:

  • External walls are unfilled cavity walls
  • The cavity is at least 50mm wide
  • The brickwork is in good condition
  • Your property is more than 20 years old (newer houses will already have insulation)
  • Walls are not exposed to driving rain
  • Your house is not at risk of flooding

How is insulation installed?

To insulate cavity walls, the installer will drill 22mm holes into the outside wall at roughly 1m intervals. Insulation will then be blown into the cavity with specialist equipment, once the holes are filled with insulation; they will be covered up and will no longer be noticeable. Insulating cavity walls is not a DIY job and you will need a registered installer, for an average sized house this will take around two hours and should be a fairly tidy job.

To find our more about how to insulate a cavity wall, visit the Energy Saving Trust website.

You may also be interested in our Home Insurance. Your mortgage lender will usually insist that buildings cover is in place and adding contents cover will give added peace of mind when it comes to protecting your home and possessions inside.

Legal & General are not responsible for the content of any external websites.

Always be cautious when undertaking any task that you're not fully familiar with as you could injure yourself or those around you, seek professional help where required.

Home Insurance Provider of the Year

Moneyfacts Consumer Awards 2017 & 2018