Image credit: National Insulation Association

According to the Energy Saving Trust, an un-insulated home loses around a third of its heat through the walls. So it comes as no surprise that there is a huge market for cavity wall insulation for all homes that are applicable.

If you live in a house built after 1920, there’s a good chance you have cavity walls. These are external walls made up of two layers with a small gap or ‘cavity’ between them. So cavity wall insulation means filling that cavity with insulating material to prevent heat escaping from your home.

Just like loft insulation, cavity wall insulation is an effective way of cutting the cost of your heating bills and reducing your CO2 emissions by keeping the heat your home generates inside rather than letting it easily escape.

In fact, the Energy Saving Trust claims you can save up to £115 a year by having cavity wall insulation. This figure is based on insulating a gas-heated, semi-detached home with three bedrooms.

You can even get a grant to help towards paying for the insulation as part of the Government’s Carbon Emissions Reduction Target (CERT). And you could even qualify for free cavity wall insulation.

In order to qualify for having cavity wall insulation you need to find out a few things first.

Do I have Cavity Walls?

Most importantly, find out if you have cavity walls, and if so are they already insulated? There are three checks you can do yourself to see if you have cavity walls.

Firstly, how old is your house? Cavity walls didn’t become a normality in construction of homes until the early 1930’s so any home built before 1932 is unlikely to have cavity walls and you may have to look into solid wall insulation or timber frame insulation. If the house was built between 1932 and 1982 then it’s highly likely you do have cavity walls. And it’s just about a certainty if your home was built post 1982.

The second think to check is the pattern of the bricks on your outside wall. There are three common styles – English bond, Flemish bond and Stretcher bond. Stretcher bond walls most likely to have cavity walls. This style is when all the bricks are laid horizontally.  You’ll be able to tell the difference as Flemish bond walls have bricks alternating between a full length brick and a half length brick and an English bond is when there are alternating rows of full and half length bricks. During these checks it’s also worth looking out for any damage to brickwork that could already be causing damp problems.

The third and final check you can do yourself is measuring the thickness of your outside wall. Cavity walls tend to be thicker than solid walls because they have the cavity gap between the internal and external brick. Measuring the thickness is easy – open your front door and measure from the outside face of the wall to the inside face of the wall. If it is less than 30cm/11.5 inches then it’s highly unlikely the walls are cavity walls. Anything over that measurement suggests you do have cavity walls.

Are my Cavity Walls Insulated?

If after these checks you think you do have cavity walls, you’ve now got to see if those cavities are insulated. If the house is less than ten years old there’s a good chance it will already have a block of insulation fitted in the cavity when the walls were initially put up. But you will have to check with your home documentation to see if there is any information from the original builder or a survey. There is a chance that an older house could have cavity wall insulation too, so again check your documentation.

Contact a professional

If you discover you have cavity walls but no insulation then your next move should be to contact a registered installer. There are no D.I.Y options with cavity wall installation; it has to be done by professionals.

To fill the cavity with insulation, the installer will drill small holes (approx 22mm in size) spaced between 1 and 1.5 metres apart. Tubing is then fitting into the wall through the holes and insulation material is blown into the cavity. The holes in the brick work are then covered up with colour-matching mortar.

Image credit: National Insulation Association

There are three common materials used to insulate the cavity walls of a house.

Blow Mineral Fibre

The first material is blow mineral fibre. Like loft insulation, the fibre consists of fibreglass or mineral wool that is pushed into the wall cavity using compressed air. There are no restrictions on this material so it can be used nationwide and is covered by BBA (British Board of Agreement) certificates.

Beads or Granules

The second type of cavity wall insulation material is polystyrene beads or granules. The beads can be installed either lose of moulded together with light sticky resin to keep them together. Polystyrene granules will stick together because of their rough shape so don’t need to be held together with resin. Like the mineral fibres, the polystyrene is blown into the cavity using compressed air and both beads and granules are covered by BAA certificates.

Foam

The final material used is a foam insulant. The foam, urea formaldehyde, is created within the wall cavity by injecting a mixture of two chemical components. The foam expands in the cavity as the two components continue to mix, filling the gap. This type of insulation is covered by British Standards BS:5618 for the material and BS5617U for the application.

Don’t worry too much about which of the three materials you want to use – your installer will know the most suitable type for your home. But do ask the installer if they’re using Energy Saving Recommended insulation as it complies with British standards and has a 25-year guarantee.

Image credit: National Insulation Association

Cavity wall insulation is one of the most cost effective ways of reducing you annual heating bills as well as reducing your CO₂ emissions. The highest percentage of the heat lost from your home is through the walls – 35 per cent is lost through walls without insulation compared to 25 per cent that is lost through the roof, 25 per cent through the windows and doors and the remaining 15 per cent through the floor if all are not insulated.

Cavity Wall Insulation Cost example

So by having your cavity walls insulated you’re going to save money in the long run. According to approximate figures from the Energy Savings Trust, based on a gas-heated semi-detached home with three bedrooms, you can make annual savings of around £115.

Cavity wall insulation instalment in a house of this size would cost in the region of £500, so you’ll have paid off the cost of the installation in just over four years.

But that’s without subsided costs that are offered by the major energy providers under the Carbon Emissions Reduction Target, and without a cavity wall insulation grant. So you could ultimately pay off the price of the installation is an average of two years according to the Energy Saving Trust.

You’ll also be saving around 610kg of CO₂ emission per year, too.

Image credit: National Insulation Association

If you’re thinking about having cavity wall insulation installed in your house you can get a little bit of help thanks to grants and offers available from the government, local authorities and energy suppliers.

Cavity wall insulation grants work very much in the same was as loft insulation grants: they were both introduced as part of the government’s Carbon Emissions Reduction Target, offer partial grants from 50 per cent to 70 per cent and have the same criteria to qualify for a free grant.

You can take up grants and offers from any of the energy supplier companies, even if you don’t use that particular supplier for you electricity and gas.

Landlord Tax Allowances

As well as grants for home owners, there are also tax allowances for private landlords. These allowances go as high as £1500 and will be available until 2015 through the Landlords Energy Saving Allowance.

The allowance a landlord receives can be used on each of the properties he or she owns, allowing the landlord to claim the costs of cavity wall insulation and solid wall insulation as well as loft insulation, draft proofing and floor insulation.

Image credit: National Insulation Association

As part of the Government’s Carbon Emissions Reduction Target (CERT), grants ranging from 50% to 100% are offered to help cover the cost of having cavity wall insulation.

Any property in the UK is eligible for a grant, but the amount depends on the type and the size of the home. Not all properties qualify for full free insulation grants, but they will be eligible for partial insulation grants between 50% and 70%.

Criteria

There are certain criteria which determine if you do qualify for a grant to cover the full cost of the cavity wall insulation.

If you receive Attendance Allowance, a tax-free benefit for over 65’s who need someone to help look after them because they are physically or mentally disabled, or you receive Child Tax Credit and earn an annual income of £15,460 or less then you’re automatically eligible for a full grant.

The same goes for anyone who receives Council Tax Credit, Housing Benefit and Income Support, however all of these must include a disability premium.

Anyone receiving Disability Living Allowance and Disability pension also qualify along with those who claim for War Disablement Pension and Industrial Injuries Disablement Benefits, but both need to include a mobility supplement or Constant Attendance Allowance.

You’re also eligible if you receive Income-based Job Seekers Allowance, State Pension Credit or Working Family Tax Credit for those with an annual income of £15,460 or less.

Image credit: National Insulation Association

Cavity wall insulation and damp are usually referred to together, especially on online forums, but although the two can be linked, having cavity wall insulation does not cause damp. It can make an existing damp issue more apparent however.

By installing cavity wall insulation you are not putting up a barrier to prevent water getting to the inside wall of your house – that’s what the outer wall does. Any moisture will move down the layer of insulation due to gravity and once it descends it can spread out and act as a channel between the outside and the inside wall.

Damp issues are caused by the condition of your outer wall so any issues with brickwork, brick pointing and leaking gutters should be resolved before having cavity wall insulation installed.

Image credit: National Insulation Association

You may read on various websites about how to install your own cavity wall insulation, but it’s highly recommended the work is conducted by a professional.

It’s not recommended not just because of the technical nature of the installation and the requirement for specialist equipment – the products involved in cavity wall insulation are hazardous. The cavity also needs to be fully filled with the correct density, which a registered installer can guarantee.

When contacting an installer you should ensure you employ one that’s registered with the National Insulation Association (NIA). By doing this you’ll be covered by the Cavity Insulation Guarantee Agency should any damage occur during the installation.

If you do have solid walls then your home should be suitable for internal or external solid wall insulation. The next decision you have to make is between internal or external insulation as the two methods are very different and have a different effect on your home.

Internal Wall Insulation

Internal wall insulation is generally cheaper than external wall insulation. It won’t change the appearance of the outside of your home, however it will reduce the floor space of the rooms the insulation is installed in as the thickness is around 100mm thick. It is however recommended that you have the installation done at the same time you’re having renovation work or re-plastering to reduce the cost of the installation and removal of furnishings from the walls. Skirting boards, door frames and external fitting swill need to be removed from the original walls and then re-applied to the inside of the new wall surface. But heavy objects and furnishings may not be able to be re-applied unless you use special fixings. And any damp issues won’t be solved by internal wall insulation, so this issue needs to be resolved before installation.

External Wall Insulation

External wall insulation benefits as it means no disruption to your household and doesn’t reduce the floor space of walls it is applied to. It was also freshen up dated outer walls and fill in any crack and gaps that may have been vulnerable to draft, but you must find out if your home is listed and you need planning permission before going ahead with installation. External insulation will increase the lifetime of a home’s wall because it protects the brick work and also reduces condensation on internal walls and reduce any damp issues you may be having, although it will not stop them all together.

Insulation boards or slabs of insulation are more traditionally used for this type of home. The slabs are friction-fitted between the studs and the rafters and the insulation board is fitted in very much the same way.

And for a more natural option you can use sheep wool insulation which can be used for roofs, walls and floors.

Installing timber frame insulation is regarded as a fairly difficult operation, so contact an expert on the difficulties of this before buying D.I.Y products.

Image credit: National Insulation Association

As part of the Government’s Carbon Emissions Reduction Target (CERT), grants ranging from 50% to 100% are offered to help cover the cost of having insulation installed into your loft.

Any property in the UK is eligible for a grant, but the amount depends on the type and the size of the home. Not all properties qualify for full free loft insulation grants, but they will be eligible for partial insulation grants between 50% and 70%.

Criteria

There are certain criteria which determine if you do qualify for a grant to cover the full cost of the loft insulation.

If you receive Attendance Allowance, a tax-free benefit for over 65’s who need someone to help look after them because they are physically or mentally disabled, or you receive Child Tax Credit and earn an annual income of £15,460 or less then you’re automatically eligible for a full grant.

The same goes for anyone who receives Council Tax Credit, Housing Benefit and Income Support, however all of these must include a disability premium.

Anyone receiving Disability Living Allowance and Disability pension also qualify along with those who claim for War Disablement Pension and Industrial Injuries Disablement Benefits, but both need to include a mobility supplement or Constant Attendance Allowance.

You’re also eligible if you receive Income-based Job Seekers Allowance, State Pension Credit or Working Family Tax Credit for those with an annual income of £15,460 or less.