Cavity Wall Insulation –FREE Home Improvement Grants 2022

Cavity Wall Insulation – A Guide For 2022


What Is Cavity Wall Insulation

Cavity Wall Insulation is a heat saving measure you can have installed to your property (assuming you have cavity walls of course) which should reduce your heating bills by around £200 -£300 per year.

This is one of the best home improvement measure you can make to your property and will pay for itself withing 3 years of installing with reduced heating bills.

Cavity Wall Insulation is an insulating material which is pumped into the cavity of your house, forming a very effective barrier to heat loss from your property.

We recommend you should have this measure to your home as it does make a great difference to the enjoyment of your home.

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How Does Cavity Wall Insulation Work?

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Cavity Wall insulation works by insulating the gap between your cavity walls with an approved insulating material such as bead, mineral wool.

This forms a barrier to heat loss and so keeps the expensive heat in your property for longer.

This should save you up to £300 off your heating bills per year.


Why Do Buildings Have Cavity Walls?

Homes and other buildings made from the 1920s and onwards were made with cavities ( a 2 -3 inch gap between the 2 walls held together with wall ties  )  to prevent rainwater from penetrating through the outer wall to the inside of the property.

However, these cavities were found to let heat escape quite quickly, so insulation was introduced in the 1960s to form a barrier to stop heat escaping to the outside.

This insulation was usually installed by drilling a hole in the walls and then insulation was pumped in to the cavity until it was full.

This process formed a blanket inside the cavity which trapped air between its fibres to create an ‘air matrix’, so reducing heat loss.



What Are The Benefits Of CWI

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Uninsulated walls account for almost a third of the heat lost from a home and uninsulated lofts account for up to 25% of heat loss.

There are many benefits to having cavity wall insulation (CWI) in your home and together with Loft Insulation they are the most cost-effective and long-lasting upgrades to your property you can make.

Indeed you will be able to recoup the costs of fitting both cavity wall insulation and loft insulation in under 5 years thanks to the savings you’ll make on your energy bills.

Your central heating system won’t have to work as hard to achieve comfortable temperatures, saving energy and money on utility bills, and reducing your carbon footprint.


What Is The Cost Of Cavity Wall Insulation


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The costs of having cavity wall insulation does depend on the size of your home and the type of insulation used.

Polyurethane foam – you should expect to pay around £20 – £25 per square meter

Glass wool is the cheaper option at around  £13 – £18 per m2.

You can calculate the Approx meterage of your home by measuring all your outside walls and then deducting the volume of your doors and windows. Times this by £20 to give you an average cost.




Example property types – Average cost guide



Detached property £725

Semi-detached property £475

Mid-terrace £370

Bungalow £430

Flat £330



Types off Walls



Single Skin Walls – Houses built before 1920 can only be treated with external or internal wall insulation.


Steel Or Timber Framed Homes


Prefabricated Concrete


Solid Walls – the bricks are usually in an uneven pattern, with some bricks being laid endways. The measurement is usually 9 inch.

Cavity Walls  – Modern homes are built using cavity walls, which feature an inner blockwork wall, with a cavity and an outer wall of brick or rendered blockwork.

The gap in between the 2 walls is filled with insulation batts to building regs


Does your walls have cavities?


Most homes built post-1920 are very likely to have cavity walls.

You can check by :

  • measuring the thickness of the wall –  if your wall is more than 260mm thick at an outside door or window, then it probably has a cavity.
  • Looking at the brick pattern – If the outer brickwork forms an even pattern with every brick laid lengthways, then they will probably have cavities.


Are All Walls Suitable for Cavity Wall Insulation?


Walls need to be in a good condition to have insulation fitted, otherwise all the benefits will be lost.

Defects like cracked render, missing pointing, leaky gutters or damp patches inside can all impact on efficiency and does lead to damage if left unresolved.

Checks are always carried out ( using a borescope)  before installation to ascertain the wall type and if suitable for CWI.

Theses checks include checking for

  • If the wall has a cavity
  • Damp or other wall defects
  • If insulation is present
  • Rubble in the cavity


If you’re in a flood risk zone or somewhere exposed to driving rain, such as by the sea, then your home might not be suitable for cavity wall insulation.


What types of cavity wall insulation are there?



There are a number of different materials used for insulating cavity walls

  1. Blown mineral wool insulation

Mineral wool is be blown into a property’s cavity walls to form an energy efficient insulating layer.

The cavities need to be clean and free from obstruction, to ensure a full fill and no cold spots

  1. Polystyrene bead insulation

This method involves blowing small balls of expanding polystyrene insulation (EPS) into existing cavity walls through small holes drilled into the wall.

Beads are quick to install, high performing and don’t absorb moisture.

Some beads have glue which bonds them together.

  1. Injected foam insulation

Polyurethane foam which is pumped into a cavity wall which solidifies and form a thick, water-repellent insulating barrier with impressive thermal performance.

Usually used where a property is in a flood risk area or has uneven cavities.

  1. Cavity insulation for new walls

Sheets of insulation batts are fitted straight into the cavity as the walls are built.

Partial fill solutions leave a 50mm gap between the cavity and external wall to reduce the chance of moisture penetrating into the home.


What Warranty Do You Get With Cavity Insulation


Cavity Insulation Guarantee Agency (CIGA) or National Insulation Association (NIA all give a 25 year warranty if the property uses one of their approved installers.


How Is CWI Installed?

Grants For Free Insulation (6)
Grants For Free Insulation (6)

Holes are drilled into the outside of the wall and feed the insulation into the cavity, taking care to ensure every nook and cranny is filled.

Once complete, the holes are filled up. The installation should only take a couple of hours, so there’s minimal disruption to your daily life. If required, any extra ventilation should now be installed.




What maintenance is required for cavity wall insulation?


We recommend good ventilation and staying on top of general property maintenance to ensure no water ingress into your walls will be sufficient.

We recommend you look for wall cracks, broken window seals, leaking gutters and make sure vents aren’t blocked.



Is Ventilation needed For cavity Wall Insulation?


Good ventilation is essential when Installing cavity wall insulation as the extra warm air ( after installation )  will carry more moisture so extra ventilation will be required to keep mould and condensation at bay.

Ventilation is now added for all new installs.


How does cavity wall insulation affect my EPC rating?

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Upgrading your cavity walls with insulation will have a positive impact on your EPC rating, and could even raise an uninsulated house up by an entire band.


Do new builds come with cavity wall insulation as standard?

Every newly built house – whether it’s constructed with cavity walls or another method – must meet or exceed the Building Regulations for energy efficiency under Approved Document L.


Do You Need Air Bricks For Cavity Insulation?

We recommend that existing air bricks are cleared and other installed if needed to allow your cavity to breath and vent any moisture to outside.


Does cavity wall insulation cause damp ?


Over 90% of homes in the UK have had CWI installed now and there is a tiny % of cases where it has been found to cause damp and mould.

This is mainly due to the way it has been installed and possibly has been installed without a proper inspection prior to its install.

If you are experiencing damp, you should contact CIGA who will arrange a free  extract and refill if found to be necessary under its 25 year warranty.


Cavity Wall Insulation How Long Does It Last?

CWi should last as long as the building it has been installed into. This is provided it has been installed correctly to regulations and there was no existing problem present at the time of install.

Realistically, you should expect at least 25 years , which is the length of its usual warranty.


Are you Eligible For A cavity Wall Insulation Grant?


The government have been giving grants to lots of properties to insulate their homes with CWI. You don’t need to be on benefits too for a lot of councils.

If you fill in our form below, we will start the process for you and if eligible, we will arrange for an installer to visit your property to survey for free.







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