Cavity Wall Insulation Cost Guide 2021

Cavity wall insulation costs haven’t come down much in recent years, but there are more government incentives that make this a great time to upgrade your home insulation. Most houses built after the 1920s have cavity walls. However, in the last 20 years, it’s become standard practice to fill these cavities with an insulating material. So if your home is older than 20 years, it’s likely that you are loosing a large portion of your home’s energy bill through these empty spaces. Adding insulation is an efficient solution to reduce your energy bills and preserve heat inside your home.

What’s In This Guide?

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Cavity Wall Insulation Costs

For a 3 / 4 bedroom semi-detached house the cost is between £600 – £ 1000. This works out at about £7.50 – £10.50 per square meter.

Cavity walls are one of the easiest ways for heat to escape from your home. Sometimes up to 1/3 of the heat can be lost this way. Therefore, by installing cavity insulation, you can save between £200 and £300 per year on your heating bills. According to statistics, the investment in cavity insulation can pay off over 3 years or less.

The cost of cavity wall insulation is determined by a number of factors, including the size of your property. Your walls must be evaluated before any cavity wall insulation is placed to ensure that they are appropriate. Before the work begins, any difficulties, such as damp or other wall faults, must be addressed. This work will need to be factored into your budget. Check to see whether there are any grants available through the Energy Company Obligations (ECO) scheme.

Property TypeAvg Cost
Detached property£750
Semi-detached property£500
Costs are estimates based on feedback from partners.

Cost Per m2

The price of cavity wall insulation mainly comes down to the size of your home, the accessibility of the walls, the type of insulation you select, and the contractor you choose. You should anticipate to pay between £22 and £26 per m2 as a general guideline. Polyurethane foam is used for this. Glass wool will be less expensive, costing between £13 and £18 per m2.

It’s important to remember that, regardless of the size and type of your home, you should be able to recoup the costs of cavity wall insulation in less than five years thanks to the energy savings.

Cavity Wall Insulation Savings & Grants

SEAI Grants

Grants are available to help with the cost of wall insulation. However, this does not imply that you are entitled to a complete award; not everyone is qualified for a full grant. You’ll need to check with your energy provider to see if you’re eligible.

If your energy provider is a member of ECO (Energy Company Obligation), you can see if you qualify for a grant. The majority of the main energy providers have agreed to participate. British Gas, EDF Energy, Eon, Npower, Scottish Power, and SSE are among them.

Each company’s criteria are a little different, but they all boil down to how much money you’d save if you installed the insulation. They are less likely to pay if it does not save much money; however, if it saves a lot of money, they are more likely to offer you the grant. Another important factor to consider is whether or not you are eligible for any benefits.

The only way to know for sure if you qualify for a grant is to chat with your energy provider. You should contact them and inquire for an ECO grant or inexpensive heating. It’s the same scheme under two different names.

Even if you are not eligible for a full grant, if your cavity is deemed ‘challenging to treat,’ you may be able to receive some assistance. If you run into problems when getting your insulation installed, you should contact your energy provider again to see if they can assist you. It’s also worth checking if you don’t have loft insulation if you don’t already have it.

Under the Energy Obligation Scheme, the government offers insulating grants (ECO).

What Are Cavity Walls?

Cavity walls are usually built of brick and consist of two thin walls separated by a gap (or cavity) with metal wall ties holding them together.

Types Of Cavity Wall Insulation

The most common type of material used in the UK is a type of polystyrene bead system. But there are other options.

Polystyrene Beads – These granules can be used in their loose form or in a sticky resin which helps them bind together. They are blown into the cavity using compressed air.

Blown Mineral Fibre – Fibre made of rock wool or fibreglass is blown into position via specialised machine.

Urea Formaldehyde Foam – A foam is created by mixing two chemicals and injecting or spraying it into the cavity. This foam then expands filling the space.

How to Determine If You Have Cavity Walls?

There are several ways to check your homes walls and they should be used together to decide. Don’t just rely on one test.

Building Age

First of all, the age of your house is probably the best indicator. Houses built before the 1920’s were generally built without cavities. And houses built within the last 20 years generally have insulated cavities.

Check The Brickwork

But, if you are not aware of the age of your house, you can check the visible brickwork to get a clue. If the walls in your building have cavity gaps, the size of each brick will be the same making a regular pattern (as seen in 2 below). On the other hand, if the size of the bricks differs with every other brick placed end-on, it means that the wall is solid (picture 1).

Wall Thickness

Another way to tell if you have cavity or solid walls is to check the thickness of the walls. It can be useful in case your brickwork has been faced with another material. Take a look at the doorways and windows. If a brick wall appears 12 inches thick, it’s an indication that you probably have got them.

Boroscope Inspection

If you are still unsure whether you have cavity walls, you can contact a registered installer to conduct a boroscope inspection. The installer drills a small hole into the wall to check suitability.

Local Planning Office

You can also contact your building control department or local planning office which should have the records of work performed on the building, including the wall insulation.

Insulation of Non-Cavity Walls

If the walls in your house are made of solid stone, there will be no cavities to insulate. In this case, you’ll need to investigate other ways of insulation such as external wall insulation.

Whilst timber or steel framed homes are not common in the UK, there are some and these won’t be suitable. If you are suggested to install cavity insulation between the outer bricklayer and the timber frame, it’s recommended to refuse it because it can cause severe damage to your house.


What Houses Are Suitable

When you’re considering wall insulation, you have to make sure that your house meets specific requirements. First of all, the walls have to be made of brick and have an unfilled cavity between the layers which is at least 2 inches wide. Make sure that the brickwork is in good condition. The external walls of your house should be easily accessible. If your walls are joined to the house of your neighbour, a cavity barrier will have to be inserted, and that can slightly increase the cost. Also, the installers sometimes refuse to work around garages or extensions.

Another requirement is that your home must not be taller than twelve metres, which is about four storeys. You have to ensure that your walls are dry because wet insulation can be harmful. So, if you spot any leakage in your walls or damp patches, you have to fix the damage before installing insulation. If your walls are exposed to rain very often, cavity insulation may not be the best choice for your house. Also, cavity insulation won’t be suitable for a house if it has steel or timber framed construction areas.

If your house meets all the requirements mentioned above, then it is suitable.

Removing Cavity Wall Insulation Cost

There are a few occasions where it is important to remove cavity wall insulation. Usually this is where your home’s insulation has failed or is allowing damp to enter. If you insulated your home with urea-formaldehyde foam, it should be removed for health concerns because it releases a harmful chemical over time.

Getting Rid of Other Insulation

Other types of insulation are a lot easier to get rid of. The insulation is sucked or pulled out, and the bricks at the bottom of your wall are removed. It is not tough, but it does take time. This costs roughly £21 per m2 on average.

Energy Savings

When you decide to improve your home’s energy efficiency, cavity wall insulation is a great place to start and when paired with spray foam insulation of the attic or loft and double glazed windows, you’ll have an energy efficient home that is both comfortable and cheap to heat. And coupled with a modern boiler you will see significant savings.

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Last Updated on November 6, 2021

Frequently Asked Questions

Who is eligible for free cavity wall insulation?

The requirements are complicated and vary depending on where you live and your specific situation. Most people who get benefits or are over the age of 60 are likely to qualify. Speak with your energy provider to see if you satisfy the requirements.

What type of cavity wall insulation is it best to use?

It all depends on how you define the term “best.” PUR is the best insulator available (Polyurethane Foam). EPS is arguably the most cost-effective alternative (Expanding Polystyrene Beads or Granules). Sheep’s wool is the most environmentally friendly alternative.

How long do you think it will take for the cavity wall insulation to pay for itself?

The length of time it takes for you to get your money back will be determined by a variety of factors including; the location of your residence, your existing home insulation, windows etc . But within 2-4 years, most households will save more than the original cost of cavity wall insulation.

Is there anything you need to do to get ready for the installation?

The setup is simple, and all of the work is done from the exterior of the house. You may need to ensure that all of the walls that need to be insulated have simple access.

How much can cavity wall insulation save you money on your energy bills?

Up to a third of a home’s heat is lost via the walls. As a result, cavity wall insulation is one of the most simple and cost-effective strategies to lower your energy expenses. Depending on the sort of property you have, you may be able to significantly lower your energy expenditures. Cavity wall insulation can save between £70 and £85 per year on heating expenditures in a terraced house. Heating expenditures in a detached home can be reduced by £200-£245 per year.


Author: Indra Gupta

Indra is an in-house writer with a love of Newcastle United and all things sustainable.

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