Insulating your solid walls could cut your heating costs considerably, because solid walls let through twice as much heat as cavity walls do. The good news is they can be insulated.

If your home was built before 1919, its external walls are probably solid rather than cavity walls. Cavity walls are made of two layers with a small gap or ‘cavity’ between them. Solid walls have no gap, so they let more heat through.

Another way to tell is by measuring the width of the wall. Look at an external wall window or door and if the brick wall is less than 260mm, then it is likely a solid wall, while if it is greater, it is probably a cavity wall. Find out about insulating your cavity wall.

If you live in a house that is not made from bricks, such as a steel or timber-framed building, insulating will be different. Find out more from the National Insulation Association.

Solid walls can be insulated – either from the inside or the outside. This will cost more than insulating a standard cavity wall, but the savings on your heating bills will be bigger too.

How much could you save by insulating your solid walls?

wall insulation table

External wall insulation involves fixing a layer of insulation material to the wall, then covering it with a special type of render (plasterwork) or cladding. The finish can be smooth, textured, painted, tiled, panelled, pebble-dashed, or finished with brick slips.

External wall insulation:

  • can be applied without disruption to the household
  • does not reduce the floor area of your home
  • renews the appearance of outer walls
  • improves weatherproofing and sound resistance.
  • fills cracks and gaps in the brickwork, which will reduce draughts
  • increases the life of your walls by protecting the brickwork
  • reduces condensation on internal walls and can help prevent damp (but will not solve rising or penetration damp)
  • is best installed at the same time as external refurbishment work to reduce the cost
  • may need planning permission - check with your local council
  • requires good access to the outer walls
  • is not recommended if the outer walls are structurally unsound and cannot be repaired