Why get cavity wall insulation?
A home can lose as much as 35% of its heat through uninsulated external walls. By investing in cavity wall insulation, you can significantly reduce the heat loss from your home. The concept of insulating a cavity wall is really very simple – it involves filling the cavity between the two skins of masonry bricks with an insulating material, which slows the movement of heat through the wall. Maintaining the heat inside your home keeps you warm and cosy when you need to be. It also works in reverse by keeping your house cooler in the summer months.
Installing cavity wall insulation in your home will not only help to decrease your heating bills by saving energy lost through the walls, it will also help to reduce your carbon footprint by limiting the amount of CO² and other greenhouse gases emitted from your property.
Many houses since the late 1930s were built with a cavity between the inner and outer walls. Because of this cavity, many of Britain’s homes have thermal performances which are well below the standards required by current building regulations. These properties suffer from unacceptably high levels of heat and energy loss through the walls. A system was introduced in the 1970s to inject insulation into these cavity walls.
Can I get cavity wall insulation?
There are two things you need to determine to see whether you can benefit from retrofitting cavity wall insulation in your home.
The first thing is to work out if you actually have cavity walls – this might seem stupid, but you can not inject insulation if there isn’t a cavity and they do look quite similar to solid walls!
A cavity wall is made up of two masonry brick walls running parallel to one another with a space (cavity) between them of at least 50mm. Masonry bricks are very absorbent, so moisture absorbed by the outer wall typically drains through the cavity, rather than coming into the home, helping to prevent damp issues. This type of wall construction became the norm in the 1930s superseding solid walls and as time has gone on, the size of the cavity between the two skins of brick has continued to grow – a typical cavity wall now is between 280-300mm thick.
You can easily identify a cavity wall by the pattern produced by the brickwork, which is known as stretcher bond, where are the bricks are running in the same direction as one another – there are no ‘half bricks’. This is obviously harder to do if your walls are cladded or painted and in this case you might need to call in a professional (although sometimes you can see original brickwork in the loft space). In addition cavity walls tend to be over 250mm in width, with more recent cavity walls closer to 300mm. If you can see lots of half bricks in your wall, you have a solid wall with no cavity, so unfortunately cavity wall insulation is a no-go. In this case, you could look into external wall insulation as an alternative.
Once you have established that you have cavity walls, you need to determine the size of the cavity and whether it has previously been insulated. A registered installer will need to come and carry out a boroscope inspection. This involves drilling a test hole into the wall and checking with a camera to see if the cavity has previously been filled and the size of the cavity (ideally over 50mm). If this shows the cavity is unfilled, you could indeed benefit from cavity wall insulation.
Although some builders began insulating cavity walls in the late 1970s, it only became compulsory under building regulations to do so during the 90s. As such there are many properties in the UK that currently have unfilled cavity walls. The good news it that these can be insulated very easily!
How does cavity wall insulation work?
If a hot room is partitioned from the cold by a wall, heat will move through the wall, eventually cooling the room until an equilibrium is reached, where the outside temperature is equal to the inside temperature. In reality this very rarely happens, because rooms tend to be heated. This means that as some heat escapes through the wall, more hot air is supplied, keeping it at a comfortable ambient temperature. If the thermal gradient is larger, (e.g. on a cold and wintry day), the movement of thermal energy across the wall will be accelerated.
Insulating a cavity wall helps to provide a thermal barrier, which slows the flow of heat out of a room considerably. By slowing down the rate at which heat escapes from the home, less heating is needed to keep the house at the required temperature. In the summer, the reverse happens; hot air outside the home can’t get in as easily, which means you don’t need to use energy to keep the home cool. Therefore in both summer and winter, cavity wall insulation can make an enormous difference to your energy bills. The process is relatively quick and inexpensive, so it is certainly worth considering.
How do you insulate cavity walls?
The first thing to note is that you cannot retrofit cavity wall insulation as a do-it-yourself job – it is a job that needs to be carried out by a professional.
Once the cavity has been confirmed by the boroscopic inspection, the installer will drill a series of 22mm diameter holes into the mortar between the bricks. With specialist equipment, the installer will then inject the cavity with the insulating material, through each of these holes. Once the whole of the cavity wall has been filled, the mortar will be made good either with plugs or mortar created to match the existing colour, so the job will be barely noticeable.
The insulating material pumped into the cavity is normally a type of glass wool, or in some instances insulating beads and once installed will offer insulation for the life of the building. The whole process should only take about 2 hours but obviously if the cavity wall area is especially large you will need to leave more time for the job to be completed.
What materials are used for cavity wall insulation?
Expanded polystyrene (EPS) foam, loose polystyrene beads, or wool. EPS is the most expensive option for a reason; it is a premium product and we would always recommend spending the extra money for the best results.
Savings from cavity wall insulation
Although the savings from cavity wall insulation vary greatly from property to property, for an average size three bedroom home, the energy savings from installing cavity wall insulation should amount to £250 per year. With an installation cost of £600-1000, the savings you create from installing the cavity wall insulation should pay for the work in under 4 years.
Can I get free cavity wall insulation?
Free cavity wall insulation is now available throughout England. If you receive one of the following benefits, you could be eligible for a grant as part of the Government’s ECO scheme.
- Child tax credit
- Pension credit
- Job seekers allowance
- Universal credit
- Income support
- Working tax credit
Paying for cavity wall insulation yourself
Unfortunately schemes like the Green Deal have now finished, but there is still some ECO funding for cavity wall insulation. The amount of funding depends on the heat demand of the property and the savings that will be generated from installing the insulation. Over time the level of funding has decreased dramatically, so it is now quite normal that a household contribution may need to be required – for example if the cost of the job is £1000, you may be required to fund half of this so £500.
If you are interested in getting cavity wall insulation installed, we have a directory of ECO-funded cavity wall installers, so please fill in the form at the bottom of this page.
- Insulating your cavity walls will help you to heat your home more efficiently, saving about £250 for a typical 3 bed home.
- Cavity wall insulation will payback in 3 – 4 years for the investment giving lower heating bills .
- According to the Energy Saving Trust, cavity wall installation can reduce carbon dioxide emissions (CO2) by 560kg, according to the Energy Saving Trust.
- Approved cavity wall installation work is guaranteed for 25 years by the CIGA (Cavity Insulation Guarantee Agency).
- Cavity wall insulation may not be suitable within your home, if it has a wall exposed to strong rainy wind.
- Do not undertake the installation if the home suffers from damp problems – seek an assessment from a professional surveyor first
- Cavity wall insulation can cost anywhere between £600 – 1000 (however with subsidies, the cost may end up at the lower end of this estimate – speak to your Energy provider).
Installing Cavity Wall Insulation
Need cavity wall insulation? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust. You can find one of these tradespeople on our easy to use local installer map.
Alternatively, if you would like us to find you a local insulation installer, just fill in the form below and we will be in touch shortly!