The prices in this guide are accurate, as of 2024*
If you’re looking to make your home as energy efficient as possible, one of the best things you can do is properly insulate the walls of your home.
Cavity wall insulation can stop heat from escaping through your walls, which in turn can reduce your energy bills considerably. This is done by drilling holes into your cavity wall, and then injecting insulation inside.
This type of insulation only works if you have cavity walls though. More modern homes tend to have solid walls or come with walls that have already been fitted with insulation. If your home was built between the 1920s and the 1980s, there is a good chance you have cavity walls. Another sign of cavity walls is uniform, lengthways fitted brickwork (alternating long and short side placed bricks are a sign of no cavity).
You can have a survey carried out on your walls to make sure cavity wall insulation would be suitable. If you’re eligible, then adding insulation could help significantly reduce both your heating bills and your carbon footprint. It will also make your home warmer.
Not to mention that cavity wall insulation is one of the top eco home improvements, adding an average of £11,764 to the value of your property.
You could spend anywhere from £650 and £6,100 to get cavity wall insulation. Prices include labour and materials. Keep in mind that the cost of labour rises in London and the South East, sometimes by as much as 20% more, on average. Find an insulation specialist in your area to get a more accurate quote on how much you might spend on cavity wall insulation.
What insulation is best for cavity walls?
There are several methods of inserting insulation into cavity walls. If you aren’t sure which would be best for you, let us know what you’re thinking and the size and age of your home, and get some free quotes today. We recommend you ask for a few quotes before you settle on a tradesperson.
| Type of cavity wall insulation | What is it? | Pros | Cons |
| Expanding polystyrene granules or beads (EPS) | Beads or granules of polystyrene that are inserted into the cavity. | Eco-friendly and recyclable Damp resistant Easy to install Durable and lightweight Water resistant (prevents damp) | Not good at insulating sound You need to clean the cavity before installation Can cause gaps in your cavity |
| Polyurethane foam (PIR) | A type of spray foam that expands as it sets. | Incredibly efficient at insulating Easy to install Won’t cause mould | Not environmentally friendly and can’t be recycled More expensive than other options Material shrinks over time |
| Cavity wall boards | Insulation boards that are fitted whilst the house is being built. | Come in a range of sizes and different types of materials An affordable option Fire resistant and usually water resistant | Hard to retrofit, so more suited for new builds Less good at insulating than other options |
| Wool fibre | Insulation made from sheep wool. Usually comes in rolls, like a blanket, or as loose fibre. | Easy to install Eco-friendly, renewable, and sustainable Fire resistant Soundproof Good at protecting from moisture / damp + mould development | More expensive than other options Less thermal efficient than other options Needs to be treated with chemicals to protect it from insects |
| Mineral fibre | Mineral fibres are molten rock that has been bound together and turned into sheets or loose fibres. | Resistant to rot Can be blown into the cavity, which makes it easy to install Cheap to install Environmentally friendly | Cavity must be clean and spacious Prone to clumping, which can cause damp Repair is expensive |
Most modern cavity wall insulations should last you up to 25 years.
As well as cavity wall insulation, you should also consider getting loft insulation installed, as it is also a great way to cut your energy bills. Check out our loft insulation cost guide to find out more on how you can make your home even more energy efficient.
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How much does cavity wall insulation cost?
How much you pay for your new cavity wall insulation will depend on the type of property you have, and its size. The bigger your home, the more expensive the total cost will be. Prices will also rise if you have a very old property, as additional remedial work may be needed. Damp also complicates things, as it will need to be dealt with before the insulation is installed.
To get a more accurate sense of how much your project will cost you, tell us what you’re looking for, and get some free quotes today.
| Type of home | Average cost 50m2 | Average cost 100m2 | Average cost 160m2 |
| Semi-detached or detached home | £1,150 – £2,500 | £1,600 – £3,200 | £,2,300 – £6,100 |
| Flat | £650 – £1,800 | £1,200 – £1,900 | £2,000 – £5,000 |
| Terraced home | £700 – £2,000 | £1,300 – £2,000 | £2,200 £4,800 |
| Bungalow | £750 – £2,200 | £1,400 – £3,800 | £2,400 – £5,500 |
How much you end up spending will also be determined by the type of cavity wall insulation you get. For example, mineral fibre insulation for 50m2 would cost roughly £717, whilst 100mm PIR cavity boards for the same area would cost about £1,911. Similarly, you could pay £2,296 for mineral fibre on 160m2 or £6,116 for PIR boards. These prices will fluctuate depending on where you live in the UK. How difficult your cavity walls are to access can also affect costs.
It takes between 1 and 4 hours to fully insulate cavity walls, depending on the type of property you have, and how big it is.
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Can you do cavity wall insulation yourself?
We do not recommend you attempt to insulate your cavity walls yourself, as you will need a registered professional to complete the job.
This is because the installation involves a difficult, technical procedure using hazardous products that need to be handled with care. Incorrectly installed insulation can cause damp or can lead to a less energy-efficient cavity wall too.
Instead, hire a skilled tradesperson to do the job for you.
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How much energy does cavity wall insulation save?
The good thing about cavity insulation is that within just a few years it will pay you back for the upfront installation costs, by saving you money on your energy bills.
This is because insulation can help trap up to a third of your home’s heat which would otherwise escape through your walls.
The below prices refer to the average UK homeowner’s annual energy bill savings, as a result of having installed cavity wall insulation.
| Detached home | Semi-detached home | Flat | Mid-terraced home | Bungalow | |
| Yearly energy bill savings | £480 | £285 | £145 | £180 | £195 |
As well as this, depending on the type of property you have, you could save between 335 – 1100 kg of CO2 a year by inserting cavity wall insulation, helping to significantly reduce your carbon footprint.
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How much does it cost to have cavity wall insulation removed?
There are a few reasons why you might want to get rid of the current insulation in your cavity walls. This process is completed either by sucking out the insulation using a vacuum or breaking up the insulation into smaller pieces using a specialist machine.
You might want to have your cavity wall insulation removed if:
- Older insulation methods are potentially toxic and could have carcinogenic health implications.
- Occasionally, DIY or unprofessional installers install insulation that is not suitable for the property (for instance in timber framed properties). Equally, poorly installed insulation with gaps in it can lead to dampness. If your insulation develops damp, it will need to be removed. Always make sure you hire professional installers. You can do so here.
- If your home suffers from a flood or fire, this could cause damage to your insulation, which will need replacing.
How much you spend on removing your cavity wall insulation will depend on the scope of the project. You can expect to pay roughly between £20 – £22 per m2 for cavity wall insulation removal. For a whole house, that could look anywhere between £1,600 – £2,600.
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What is the U value of cavity wall insulation?
The U value, also known as thermal transmittance, measures the rate of heat loss of a fabric.
The equation for the U value looks like this:
R represents thermal resistance (of your cavity wall insulation). The U value is measured in Watts-Per-Metre-Square-Kelvin (W/m2K).
Building regulations will check your U value to make sure your insulation complies with the required amount. The lower your value, the better. Building regulations require your cavity walls to be no less than 0.18 (W/m2K).
A skilled tradesperson will make sure your insulation conforms to all building regulations. You can hire an insulator here.
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Conclusions
Cavity wall insulation is one of the most effective ways to stop heat escaping from your home, reducing your energy bills and carbon footprint. It’s no surprise that it’s currently a top eco home improvement, as properly insulated walls can add over £11,000 to the value of your home.
Your insulator will be able to advise you on what type of insulation you should get, according to the age and layout of your home. How much you end up spending will mostly depend on the size of your property.
For a more accurate quote on the total cost of adding cavity wall insulation to your home, let us know what you’re thinking, and get some free quotes today.
*The Rated People cost guides are produced in collaboration with the quote-building platform PriceBuilder, and a range of tradespeople across the 30+ trades on our platform were consulted. Please note that the prices included are for guidance only – how much you end up spending will depend on the specific requirements of your project.
