Cost of Cavity Wall Insulation & Potential Savings

How much does cavity wall insulation cost? As with many home improvement projects, there’s no fixed answer when it comes to the estimates; with a number of factors determining the price you might expect to pay.

This can things such as:

  • Location – where you live can have a bearing on the costs
  • Property Type – As you might expect, the cost will be dependent on whether you live in a flat, bungalow, semi-detached or detached house
  • Difficulty – If there are walls that pose more difficulty in accessing, this might have an effect on the price as well

Wherever you live, or whatever your property type, there is going to be a cost attached to insulating your cavity walls. Depending on your location and financial situation, you may be available for some kind of external wall insulation grant, so might be worth checking with your local authority.

On the assumption that you will be paying for the work, then the average cost of cavity wall insulation work across the country, according to the Energy Savings Trust, is:

  • Flat – £330
  • Bungalow – £430
  • Mid-terrace – £370
  • Semi-Detached – £475
  • Detached – £725

However, while this can clearly be a hefty expense for many households, the benefits to your long-term finances can be marked and you should expect your insulation to have paid for itself within 5 years thanks to savings made on your energy bills.

Indeed, the Energy Saving Trust estimate that your home could save anywhere between £100 to £250 per year on your energy bills, depending on the type of property.

In this article we’ll be exploring the different types of cavity wall insulation that you can install in your home or other property, looking at what which works best for your circumstances, your walls types and your budget.

Why Do You Need Cavity Wall Insulation?

Most homes built in the United Kingdom over the last century will have been constructed with cavity walls. These are walls comprised from two thinner walls, typically brick, that have a small gap (the cavity) in between, and fixed together by wall ties.

Older homes, essentially homes built between 1920 and the end of the last century, tended to leave this cavity empty. Given that up to a third of your homes’ heat is lost through the walls, then you have the opportunity to fill in this space between the brickwork with a wall insulation material, offering an effective and cost-friendly method of retaining the heat.

This, in turn, can help you reduce your energy costs, which is good for the environment and, crucially, good for your finances.

The Different Types

There are basically three types of material used in a standard home insulation. These are:

  • Mineral Fibre Wool – The most common type of wall insulation, and very similar to the type of insulation that you might find sitting like a quilt in your loft. However, the slight difference when installed into the wall cavities is that the fibre is broken down into small pieces to allow to be blown in. For the insulation to work, it’s essential that the material is kept completely dry.
  • Polystyrene Insulation – Made from polystyrene beads and granules, this is another popular type thanks to their highly effective heat retention properties when packed into the gaps in the walls. One thing to be cautious of though, with this type of material, is that they do have a bit of a tendency to pour out of bricks containing air gaps, or if you ever create a hole in the wall when drilling.
  • Foam – Foam is generally considered to be the material offering the best insulation properties when installed into your wall cavities. However, the installation process is a more difficult process than the other two, and requires expert attention from a qualified installer. Foam is also known to degrade somewhat in the long-term in some cases.

Whichever material you decide to use, it should always conform to industry standards in terms of quality and safety, complying with the regulations set out by the British Standards Institution (BSI).

Working Out Your Wall Type

To work out if cavity wall insulation is right for you, understanding the type of wall your house has is important.

Obviously, if you don’t have cavity walls, then you’ll need to consider alternative forms of home insulation.

The Age of the Property

A starting point for working out your wall type is to know the age of the property. The majority of homes built in the UK since the 1920s will have brick walls, either comprising a single solid wall, or a cavity construction. If you live in a pre-1920s construction, then it is extremely unlikely to have cavity walls.

Check the Appearance of the Brickwork

Take a look at the brickwork on your property, as this offers you further clues as to its type of construction.

Usually, if it’s a cavity wall, then the bricks will all be laid in a uniform pattern, and all sideways facing. Solid walls, on the other hand, will have a more alternating pattern, and some of the bricks will have their smaller end facing outwards.

Measure the Width

Of course, it’s possible that the brickwork in the home is covered.  Therefore, you might need to check the width of the walls to give you an idea of its type.

Use a window or doorframe as a guide point as a measuring point.

  • If the width of the brickwork is greater than 260mm the likelihood is that you have a cavity.
  • Less than 260mm, then it is more likely to be a solid wall.

Is it actually brickwork?

While the majority of homes will be brick-built, there are some notable alternatives in existence. If your home is timber or steel-framed, or perhaps a pre-fabricated concrete, then obviously, you’ll need to explore alternative solutions, such as a wall insulation board.

Does Your Home Actually Need Cavity Wall Insulation?

Having ascertained that your home does have a cavity wall structure, it does not necessarily follow that you need to have insulation installed.

You Already Have It

If you are living in a home that was built sometime in the last two decades, then there’s a very real possibility that it has already been insulated. You can find this out by getting a borescope inspection from a qualified insulation installer, which involves drilling a small hole in the external wall to determine the presence of any material inside.

Alternatively, if the prospect of drilling into your wall isn’t too appealing, you could run a check with your local authority building control department, who may have details of any insulation on their records.

Meeting the Right Criteria

Before embarking on any external wall installation, you’ll need to get the walls surveyed from a qualified installer, who will check the overall suitability, ensuring that your home meets specific criteria, such as:

  • Making sure that the property DOES have cavity walls, and that they actually ARE empty cavities
  • All brickwork is in good condition
  • That the cavity is at least 50mm (2 inches) in width
  • That the cavity does not have any debris or rubble within it
  • That your home is not more than 12m high
  • That the home is not in an area at risk of flooding
  • That you have accessible external walls. Note that some installers will not carry out insulation work around adjoining garages or conservatories
  • That internal walls are dry. If your home has a problem with damp then you MUST resolve this before carrying out the insulation. Furthermore, if the walls are frequently exposed to driving rain conditions, cavity wall insulation is not recommended.

How is the Work Carried Out?

The starting point is always to ensure that you are using the services of a qualified cavity wall insulation installer. Word of mouth, local and online searches and review sites will invariably allow you to find a suitable person or company within your locality.

Your approved professional will start by making thorough checks on the walls to ensure that they are dry and in keeping with the criteria laid out above.

They then proceed to drill a number of small holes in the external walls, allowing them access to blow the insulation material into the cavity using special tools for the task.

Once completed, they will then fill the holes in, and ensure that there is no mess, or any of the insulation material leaking out from any areas.

It should also be noted that this is an external job, meaning that no work need be carried out inside your home at all.

How Long Should it Take?

For a standard sized UK home, where the walls are easily accessed, the whole process should take approximately 2 hours to complete.

Following the installation, you should expect written documentation that shows the work was carried out in compliance with building regulation and issuance of a guarantee from the Cavity Insulation Guarantee Agency (CIGA).

Don’t be surprised, either, if you receive a visit from the local authority who can run spot checks to ensure installers are carrying out work of a good standard.

Loft, Roof and Floor Insulation

The savings you make on your energy bills can be further enhanced if you combine your cavity wall work with other kinds of insulation around the home.

Loft and Roof Insulation cost

With up to 25% of heat lost through the roof, installing loft installation offers a super easy fix that can have a huge impact on your bills. As long as the loft is free from damp or condensation, then installation of wool fibre or specific loft insulation boards can provide long-term heat retention for your home.

Floor Insulation cost

Further savings can be made to your energy bills by introducing insulation to your floors and skirting boards; both of which can cause further heat leakage in your home.

This can be achieved by applying mineral wool insulation beneath the floorboards, while applying a sealant to close gaps in the skirting.

Typically, you would only be insulating the ground floor, acting as an additional barrier to effective wall and loft protection in the house.


Cavity wall insulation can be a hugely effective method for preventing heat loss in your home; playing a major part in turning your property into an energy efficient dwelling. Providing a temperate atmosphere in which to live, and cutting your utility bills significantly from day one, and in the long-term.

Suitably installed insulation can also have a bearing on future house prices.

Of course, for this to be a success, the insulation work needs to be appropriate for your property and carried out correctly.

Understand the wall types you have at your property, whether they are suitable for insulation, and the material most appropriate for your home.

Then seek the advice and service of a professionally qualified, industry-approved, and well recommended cavity wall insulation installer, who can carry out the pre-work checks, and the work itself. Ensuring a quality job that will provide you with years of added warmth and savings on the monthly budget.

Leave a Reply

Your email address will not be published. Required fields are marked *