Wall insulation

Did you know that around a third of all the heat lost in an uninsulated home goes 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.

Cavity walls and solid walls

Other types of wall

Most houses built from the 1990s onwards were built with insulation in the walls to keep the heat in, but if your house is older than that it may not have any wall insulation at all. If this is the case then you're paying good money to heat the outside air, instead of just heating your home. Luckily 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 £140 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 walls and solid walls  

Houses in the UK mostly have either solid walls or cavity walls:

  • a cavity wall is actually 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 what sort of walls you have

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 like this:

If your home has solid walls, the bricks will have an alternating pattern like this:

If the brickwork has been covered, you can also tell by measuring the width of the wall. Go to 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 can be thicker still but are usually solid.

If your home has cavity walls, find out about cavity wall insulation.

If your home has solid walls, find out about solid wall insulation.


Other types of wall  

Some houses aren't made from brick or stone at all, and so don't fit neatly into these two categories - for example, steel-frame and timber-frame buildings, and houses made from pre-fabricated concrete.

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 more advice, and to find an installer who can help you, contact the National Insulation Association.