The average cost of cavity
wall insulation is roughly £200 per wall
Pricing guides

How much does cavity wall insulation cost?

The cavity wall insulation costs in this article are correct as of 2022

Much of the heat in our homes escapes through the walls, raising your heating bill and lowering your home’s energy efficiency.

The best solution for this is cavity wall insulation, which can help your home to retain heat and save money in the long run.

If you have solid walls, there are also ways you can insulate them to conserve energy and cut down on your bills.

We’ve put together this guide so you can get a good idea of wall insulation costs.

Cavity wall insulation costs

Cavity wall insulation can be done in most homes where the exterior walls are composed of two layers of brick with a gap, or cavity, in between.

Most homes in the UK built after the 1920s were built like this, and while they are now built with insulation already in place, there are many homes where the gap is unfilled, allowing for heat to leak out of the building.

Installing the insulation is a fairly simple matter of drilling small holes into the exterior brickwork, then injecting the insulating material through into the cavity.

Common materials include mineral wool, polystyrene balls and expanding foam. The holes are then filled up and the job is complete - typically, it can be carried out and completed in a few hours.


The cost depends on the size of your property and the walls to be insulated, but a general rule of thumb is that it will cost around £200 per each two-storey wall.

A mid-terraced house with only two external walls could cost under £400, while a detached property may be £800 or more.

Bungalows are cheaper due to their height, with cavity wall insulation for a detached bungalow likely to cost around £400.

If you are unsure whether or not cavity wall insulation is applicable for your property, you can speak to a specialist installer to carry out an inspection.

It is important that any issues such as damp are cleared up before cavity wall insulation is installed, to ensure it works to its full potential.

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External wall insulation costs

If you have solid walls in your property, with no cavity inside - more common in homes built before 1920 - then there are other options for insulating them.

The two main choices are internal wall insulation - fitting stud walls or insulating panels to your walls, or adding insulating material to the exterior walls and then rendering over it.

These are much bigger jobs that cavity wall insulation, and will have a large impact on your home - taking away some of your internal space and requiring total redecoration in the case of internal insulation, and changing the entire appearance of your home in the case of external insulation. 


Internal wall insulation is more expensive than cavity wall insulation, and could cost between £4,000 and more than £15,000 depending on the size of your property.

Solid wall insulation is more expensive again. A rough price for external wall insulation is around £100 per square metre, meaning that for a terraced house, it could cost around £7,000, while for a large detached property, it could cost more than £20,000. 


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