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.

The most popular type of insulation obtained through the ECO grant is cavity wall insulation.

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

The cavity between the walls is filled with an insulating material (usually rockwool or bead) which serves as a barrier to allowing the heat to escape through the walls.

Cavity wall insulation usually costs around £20 per m2 and you can expect to pay around £1200 for an average semi if you pay privately.

Cavity Wall insulation is usually made of fibre glass or bead and is injected into your cavity walls to provide a barrier to heat escaping to outside.

Holes are drilled to access the cavity which are then closed up with mortar. The job usually takes about 4 hours to complete

 

Why Have Cavity Wall Insulation?

A warmer home – more than a third of heat lost from an uninsulated home escapes through the walls, and up to a quarter through an uninsulated loft. Having the walls insulated will ensure your home remains warm without the need to turn on your heating.

Reduced Bills – not only will you benefit from a warmer home for you and your family, you could save between £90 to £270 per year depending on your property type and size. A loft insulation could also save you up to £65 a year.

Doing your bit for the environment – with an increasing pressure on households to reduce their carbon footprints, homes with cavity wall insulation will be reducing the amount of energy used to heat the home as well as their carbon footprint.

The Benefits of Cavity Wall Insulation

Save you around £140 a year.
Average cost is £8 per square meter. Average house will cost £400- £500

Cavity walls insulation is one of the most cost effective ways to save energy and money in your home. Around 35% all the heat lost in an un-insulated home is through the Cavity walls. 90% of homes have now had it installed.

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.

 

1. You can save up to £300 a year on your energy bills.

2. You will improve your home energy efficiency rating making your house more attractive to home buyers

3. Your Home will get warm more quickly and keep the heat in for longer.

4. Your home will be a lot cooler in the summer as the insulation helps to stop heat entering the house.

5. You will reduce your carbon footprint with more efficient fuel consumption

 

How Does Cavity Wall Insulation Work?

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.

 

 

 

What are Cavity Walls & 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.

Walls were built this way to stop damp from penetrating the house so that any moisture penetration would drop into the cavity harmlessly.

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.

 

Does your walls have cavities?

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

You can easily tell if your home has cavity walls by measuring their width by the windows or doors. A solid wall will measure below 260 mm and a cavity wall is usually around 300 mm.

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.

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

What Is The Cost Of Cavity Wall Insulation

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

 

 

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

2. 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.

3. 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.

4. 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?

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?

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.

 

The Best Insulation for Cavity Walls

Traditional Cavity Wall Insulation for homes built from the 1930s onwards uses Blow in Rockwool or bead insulation .

A 25 mm hole is drilled into your walls and the insulation material is blown into the cavity filling all the crooks and crevices.

This insulation is easily retrofitted to your home and takes only a few hours to do.

New builds from The 90s onwards usually have insulation batts fitted as the walls are built. We recommend that you check your walls to see if this is the case as some homes have been missed in the early days.

 

Wall Cavity Insulation Removal

Cavity wall extraction is the removal of the insulation (usually Rockwool or bead insulation ) from cavity space between your wall using specialist equipment.

Cavity wall insulation removal is usually required when the insulation previously used is no longer effective or you are having problems with condensation and mould.

This guide is to help you understand the process of cavity wall extraction, the costs associated with it and the benefits to having this done.

 

 

Benefits of Getting Cavity Insulation Removed

The benefits are :

• Warmer house with reduced heat bills.
• Less chance of mould appearing in the future
• Reduced chance of damp or make removal of damp easier
• Increase Of House value .

• Can contribute to helping with health issues.
• The effects of wrongly installed and failed insulation are almost immediately resolved once the cavity wall insulation is removed and the property is cleaned and aired.

 

When is Cavity Wall Extraction Required?

Cavity wall extraction is needed when you suspect you have failed cavity wall insulation or the insulation has been poorly installed.

This measure is becoming increasingly popular with home owners who are having problems with their walls such as damp, cold spots and mould.

Removing cavity wall insulation allows you to make room for more effective insulation, which in turn can save you money, reduce energy usage, and remove any potential damp.

Grants are available too for many people on a low income.

 

Why Might I Need Cavity Wall Extraction?

Cavity insulation fitted in the past used less efficient materials which had a much shorter lifespan.

Whilst this measure has always come with a 25 year warranty, the materials used didn’t use to have the same strict KIWA certifications that it now comes with.

The main causes of inefficient insulation are:

• Replaced windows can cause the insulation to fall out causing void areas. This will allow damp transfer from the outer skin.
• Flooding is a major cause needing insulation removed as the water gets into the material and creates damp allowing water to pass from the external wall into the home.
• Incorrect installation or means the effect on your home is less than what it should be or non-existent. This can happen if the drill holes to insert the insulation where incorrectly spaced and would lead to cold spots.
• Incorrect materials were used such as urea-formaldehyde. This breaks down to dust-like particles and sits at the bottom of the cavity giving no insulation benefit at all.

 

How Can I Tell if I Need Extraction Of Insulation?

Tell-tale symptoms will include

• Cold patches on your internal walls
• A build-up of condensation and mould on internal walls
• Decorative surfaces becoming stained with paint flaking off
• You have damp areas and your property smells of damp

• Your walls are wet due to flooding, faults in brickwork or burst pipes
• You are in a high risk area near the sea .
• Feel like your house isn’t retaining heat and your energy bills seem to be more expensive than they should be
• Your external walls have been damaged

Have an Insulation Survey

Engage a reputable insulation company to investigate your walls.

They will create a heat loss survey using thermal cameras and borescopes which will highlight any cold spots in your walls and if extraction is necessary.

 

What Materials that can be extracted?

Expanded polystyrene
Loose and/or bonded Urea Formaldehyde Insulation
Rockwool Mineral Fibre
Whitewood Glass Mineral Fibre

 

 

How Is The Insulation Removed?

All work should be carried out by OSCAR accredited technicians who will carry out the work effectively and issue all certification and 25 year warranty.

A purpose-built insulation removal system is used to collect all the insulation that occupies the cavity.

It is an industrial vacuum cleaner which uses air pressure to suck up the insulation into a bag. Henry is not used. 🙂

The powerful motor will ensure that all existing insulation material is removed from every crevice.

 

How Long Will It Take?

The process to extract and refill usually takes 2 – 3 days to complete.

You do not need to vacate your property but there can be a lot of noise via the machines.

 

How Much Does Cavity Wall Insulation Removal Cost

You should expect to pay around £20 -£25 a square meter for removal.

Typical house costs £1500 – £2000

To refill would would cost up to £1200

The Cavity Wall Extraction Process

A complete technical survey is carried out and fully risk assessed prior to any work being carried out.
All works are carried out by Oscar approved cavity wall extractors
All works are non-disruptive to neighbouring properties insulation.

 

Grant Funding

Grant funding is available for re-blowing cavity wall insulation for electric heated homes only . Gas heated homes will be included from Eco 4 in July 2022

The amount of grant and the cost of the works is usually covered by a 100% grant from The Government subject to it meeting the requirements below:

• The cavity was not appropriately cleared prior to the insulation installation
• Your property’s location is within a high wind and rain exposure area causing penetrating damp
• Your property suffers from damage to external walls such as cracks within the render, pointing or brickwork.
• Your property’s structure is not appropriate for cavity insulation
• It has not been installed correctly
• The cavity is suffering from blockages as a result of building works
• The insulation is aging and suffering from slumping.

 

Top 5 Cavity Wall Insulation Problems

1. WET INSULATION

If your cavity wall insulation is wet or defective, this can eventually lead to some nasty bills. You will have mould problems and redecorating costs.

 

2.WALL TIE REPLACEMENT

Wall ties play an essential role in holding the structure of a property together.

When cavity wall insulation becomes wet, it will eventually sag and clump around a wall tie.

Seeing as most older wall ties are galvanized steel, they’re prone to rust and corrosion.

To avoid any structural damage to your property, these ties must be replaced which typically costs £1000 to £1500.

 

3.WALL RENDERING

It is likely that your rendered wall would have cracked as the wall ties begin to swell, so not only will you have to pay out on wall tie replacement but potentially the cost to re-render your property. This could cost you an excess of £2500.

 

4.HEATING BILLS RISING

Another subtle cost that you could incur if your cavity wall insulation is failing is a rise in your heating bills.

Most fail to notice this, but as your insulation deteriorates, it becomes easier for heat to escape your property.

This results in you having to use more gas and electricity to heat your home.

 

5.WATER INGRESS

Finally, if water does manage to ingress from the exterior to interior wall it will eventually work its way into the gypsum skim on your wall.

As moisture works its way into the plaster, the plaster will lose its adheration to the wall and blow.

Whilst the cost to repair this might be relatively low, £100-£300, unfortunately it is a recurring cost. Until the source of the problem is resolved, this cycle will continue.

 

 

More Useful Resources & Other Grants