In an uninsulated home, 33% of the heat is lost through the walls. You heard that right, a third of the heat you’re paying for is escaping. Insulating the walls is a major step towards saving money and energy.

What are your walls made of?

Different walls in different homes are made up of different stuff. Houses in the UK are generally either solid or cavity walls. First step is to find out which you have:

  • Cavity walls: These are made up of two layers with a gap between them. Since the 1920s, walls were built this way to stop rainwater leaking into homes. If you have these kinds of walls, you can fill that gap with insulation.
  • Solid walls: As you’ve probably guessed, solid walls don’t have that gap. This is typical in older buildings and means you have to place your insulation on the outside or inside of the walls. 

Cavity wall insulation

If you have cavity walls, you can insulate them by injecting insulation material from the outside in. Imagine drawing a clock face on your wall – the insulation would be injected into the wall at 12, 3, 6 and 9 o’clock. After the work is finished, the holes are covered in cement – you wouldn’t know they were ever there. 

It’s a job you can’t do yourself, but an average house shouldn’t take a registered installer more than a couple of hours. 

Solid wall insulation

Insulating solid walls is a bigger job. You can get external or internal wall insulation – meaning you can insulate the outside or the inside of your wall. 

Internal solid wall insulation

This involves layering material (like plasterboard) over your wall inside. This internal option has a few advantages:

  • It’s less expensive than external solid wall insulation
  • It doesn’t ruin the look of period properties or other beautiful buildings
  • It works in conservation areas or for listed buildings
  • It works for flats or maisonettes where you can’t use external insulation for one level of the building

External solid wall insulation

This means fixing insulation to the outside of the building. If your wall is old or cracked it’ll have to be repaired first. Here are the advantages:

  • It doesn’t reduce the size of your rooms or eat into square footage
  • It’s less disruptive (other than your garden being messy whilst it’s done!)
  • It makes your home soundproof and weather resistant

Costs and savings

The price depends on the condition of the walls and of course, property size. 

Cavity wall insulation generally costs around £200 per each two storey wall. So, a mid-terraced house would cost around £400 and a detached home would be around £800.

Solid wall insulation is more expensive. Internal wall insulation ranges from around £4,000 to £15,000 and external wall insulation from £7,000 to £20,000+. 

There’s no denying that wall insulation comes with a hefty price tag, but savings can be as high as £375 a year.