Cavity Wall Insulation Prices

A Warmer Home

Wall Soundproofing From External Noise

Prices and Sound Advice

With over 35% of a home’s heat lost through the walls, it’s easy to see why over 13 million people have chosen to install cavity wall insulation.

There is no denying that cavity wall insulation works and when combined with loft insulation, reduces heating bills so dramatically that most consumers get their money back in less than 6 years through energy savings.

But did you know that out of 13 million homes insulated, over 800,000 installations have failed? One installer went bust after receiving up to 50 complaints a month; some issues were so devasting that consumers had to move out of their homes while remedial work was carried out (source).

There’s even a new industry that’s appeared in recent years – cavity wall insulation removal services (source).

What’s going on?

On this page, we’ll look at:

  • How much cavity wall insulation costs.
  • The truth about those “free” grants.
  • Houses that shouldn’t have cavity wall insulation.
  • Some simple checks you can do to determine if your property is suitable for cavity wall insulation.
  • A realistic guide to how much you can save off your energy bill (not exaggerated nonsense spouted by sales staff)

An Honest Look at Cavity Wall Insulation Prices

And why so many people have issues after its installation

We got in touch with 14 cavity wall installers and asked them for prices to install their recommended insulation.

Below you can see an average of the prices given to us.

You’ll probably want to keep reading, though; we can help you decide if cavity wall insulation is right for you.

Our Price Guide – Cavity Wall Insulation Cost

Here are the details of the project:

  • Visually inspect interior walls for signs of existing damp.
  • Inspect external walls for signs of damp.
  • Inspect exterior walls for defects that could lead to damp penetration (failed mortar joints, cracks etc.).
  • Check the property is suitable for cavity wall insulation.
  • Drill holes at specified intervals.
  • Blow insulation into the walls until full.
  • Seal holes and touch up with paint if required.
Property:Average Price:
Small Detached£625
Low level Flat£390

Is Your Home a Good Candidate For Cavity Wall Insulation?

Most homes in the UK are built with an inner and an outer wall with the space between the two referred to as a cavity. Modern homes will have this void filled during construction, and the entire build will be designed so that water and moisture can’t come into contact with the insulation.

Older homes are slightly different; they were never designed to have the cavity filled. In fact, most cavities are designed to allow any water that reaches this void to run down to the ground level and drain away without entering the home.

Unfortunately, some older homes or those poorly constructed, will allow water to enter the cavity, perhaps through failed or weak masonry or even cracks in the external walls. This doesn’t pose a problem – until the cavity wall is filled with insulation.

Insulation holds water, and if it gets wet, moisture will soak through the inner wall and into the plaster. Black mould, damp patches, failed plaster and rot is just the beginning. Some consumers have experienced such terrible damp problems that they’ve had to pay tens of thousands of pounds to get the insulation removed, the house dried and new plastering and other repairs completed. 

A Simple First Check

The vast majority of cavity wall insulation complaints have come from consumers living in western and north-western regions, this is due to wind-driven rain that penetrates the outer wall, soaks the insulation and causes dampness on the internal walls.

The first check any consumer should do is look at the image below which highlights areas of the UK that are prone to wind-driven rain:

Wind and rain chart UK

If you live in a high-risk area, you had better make sure that your north and west-facing walls are in excellent condition. If they’re not, there’s a very real chance you could experience problems.

Cavity wall installers are supposed to fully inspect the walls of each house they work on for suitability and defects, but many don’t.

Further Checks

If you live in a high-risk area and also in an older property, or any property with a history of leaks, condensation or general dampness, there are a few things you can check yourself:

  • Look for obvious cracks in external walls.
  • Check for damp patches anywhere on the external walls.
  • Run your finger along the mortar joints, check if the cement is loose, flaky or crumbly.
  • Check for previous repairs to damp issues.
  • Does the property have leak-prone concrete guttering?
  • Speak to neighbours in similar houses and ask about any cavity wall insulation they have had fitted.
  • Post a question onto a local online/Facebook group and ask others in the wider area about their experiences with cavity wall insulation.

Getting a Price For Cavity Wall Insulation

Given that over 6% of cavity wall insulations will develop a defect, we suggest you get at least 3 quotes from reputable installers and ask questions about any issues with your property or its location. Highlight and point out any obvious defects such as gutter leaks, poor masonry or cracks and see what suggestions you are given from their surveyor. 

If their surveyor isn’t surveying but is just measuring up and trying to sell you their product, you might want to avoid the company.

If in doubt, get a second opinion from an independent surveyor.

Is Cavity Wall Insulation Really That Bad? The Next PPI Scandal?

The vast majority of installations (94%) are trouble-free, and the potential energy savings are impressive. However, if you live in the wrong house in the wrong place, you could find this insulation causes thousands of pounds of damage.

One Welsh MP even described the cavity wall insulation scandal in Wales as the “next PPI”.

The issue is related to government grants which cover all or part of the cost. With so much free cash flowing from government coffers, miss-selling has become a major problem and is set to worsen as the government has now extended the grant scheme.

Should you consider cavity wall insulation? 

Absolutely, just do your homework first, especially if you live in an older home in a wind-swept area.

Can You Really Get This Insulation For Free? Grants Explained.

I’ve lost count of how many times the government has offered grants and discounts for energy-saving products.

The latest scheme was called the “Green Homes Grant”, and it lasted all of six months before being cancelled in March 2021.

To complicate matters, the government is now directing consumers to their local authority, who each have a finite allocation of funds to cover green home improvements.

As of April 2021, you can still get free cavity wall insulation through your local authority or energy provider if:

  • Your walls are difficult to insulate (i.e. not just regular walls) or:
  • You or someone in your home receives benefits.
  • You are on a low income.

Start by contacting your energy supplier; they should have an eligibility calculator (here’s one from Eon). Failing that, try the main government site, which may redirect you to your local authority.

Be wary of websites that claim anyone can get free cavity wall insulation; if you can’t get a grant, they’ll likely try to sell you a loan or sell your details on. Unsurprisingly, these scams started even before the grant scheme was launched.

Realistic Cost Savings

Cavity wall insulation is big business, and with free government grants and subsidies, there’s plenty of incentives for businesses to exaggerate the cost savings the consumer can expect.

We’ve cut through the fluff and done our own research, and in the table below, you can see how much money you can save each year. This data is drawn from several reliable sources, including the Energy Saving Trust.

We believe that an insulated detached property will significantly reduce the heating bills and that the installation cost will be recouped in around 3 years.

Semi-detached and terraced homes along with flat are already partially insulated by their party walls, so it takes longer to recoup the cost – up to 6 years.

How long it actually takes will depend on other factors such as the amount and quality of loft insulation, double/triple glazing etc. and the type of heating the home has.

Cavity wall insulation cost savings
Property:Savings Per Year:
Large Detached£320
Low level Flat£105

Get a Fixed Price for Cavity Wall Insulation

We hope you found our guide to cavity wall insulation insightful.

We can help you get custom quotes from approved installers in your area.

To get started, tap the button below and fill out the contact form:

Cavity Wall Insulation

Get a Custom Price


When Were These Wall Insulation Prices Published?

We sourced prices for cavity wall insulation in early 2021 and published this guide in early April 2021.

Is Cavity Wall Insulation Good at Soundproofing?

Yes, cavity wall insulation is great at soundproofing. It can reduce direct noise from outside and prevent the cavity from echoing and amplifying noises from other rooms and neighbours.

If you want to block noise from outside, we suggest you first start with the cheapest options first, which are cavity wall insulation and secondary glazing, before considering more expensive options such as wall soundproofing.

Can Walls be Insulated From The Outside?

Our prices are for cavity wall insulation. If your property is constructed from a single wall and doesn’t have a cavity, you can install internal wall insulation, which takes up space indoors or fit insulation to the outer walls, which is expensive and alters the appearance of the property.

You may wish to consider wall rendering as this adds mass to the external wall and keeps in some heat.

Do These Prices Include VAT?

Most of the firms we contacted were VAT registered and charged VAT.

We’ve included VAT in our wall insulating price guide on this page when the firm charged it.

How Effective is Cavity Wall Insulation?

Cavity wall insulation is one of the best ways to insulate a home and reduce heating bills. Loft insulation should also be considered, the current recommended thickness is 270mm.

How Long Does it Take to Fit The Insulation?

It takes a team of two about 2-3 hours to complete the insulation project, depending on the property’s size, of course.

Can This Product be Fitted DIY?

Anyone can hire insulation machines and buy the insulation, but as cavity wall insulation isn’t too expensive, most DIYers prefer to use the services of a professional.

Experienced contractors will also make sure no voids are left that could lead to cold patches.

I Think Your Prices are Too High/Low, What Gives?

The cavity wall insulation prices displayed on this page are an average of the quotes given to use by 14 specialist firms.

They are also in line with published price lists from numerous other companies.

Where Can I Get a Custom Insulating Price?

You can post details of your insulating project on Rated People, a site where tradespeople are vetted by staff and reviewed by their past customers.

Discover More Price Guides:

By Quotation Check

Loft Insulation

If you’re considering cavity wall insulation, then check our guide to loft insulation which is also very effective at trapping heat in the home. 

Wall Soundproofing

This is how much the experts told us it would cost to soundproof a wall from noisy neighbours or street traffic. Prices are displayed per square metre so you can easily price your project.

Double Glazing

Sealed double glazing units not only block out external noise they also help to make the property more thermally efficient as the windows of any home are where lots of heat is lost.

Their prices for roofline installations were correct; we were given quotes from several firms, all were similar to [Quotaton Check’s]

Thanks, the estimates I was given were slightly below those you suggested but only by a fraction. When did you last update these prices?

Quotation Check has a database of prices for popular home improvement tasks. Check out their excellent information here.

Explore our benchmark prices for things like house rendering, plastering, garden improvements, driveways and much more.

Go see the prices on the Quotation Checker website; they’re suggesting a price for a new roof that’s much lower than that.