A Guide to Cavity Wall Insulation
Cavity walls are responsible for up to 35% of heat loss from the average UK home, this leads to higher energy bills as central heating makes up for this heat deficit.
Many homes built after the 1930s have two walls with a gap between, known as a cavity wall. This was designed to keep rainwater from getting in, but also means there can be heat loss between the two walls.
It is possible to insulate cavity walls and increase the energy efficiency of your home. Read on to learn more about cavity wall insulation, the cost and the benefits.
What is Cavity Wall Insulation?
Cavity wall insulation is made up of insulating materials such as mineral wool. It is installed in your home by drilling small holes into your outside walls and blowing the material into the gap until it is filled. It works by trapping the air in an insulation material that has been sprayed or injected into the cavity. The materials help trap warm air and also prevents air circulating, thus preventing heat loss by both conduction and convection.
How Long Will Cavity Wall Insulation Last?
If you have your cavity wall installed by a company who provide a CIG/GDGC guarantee, then it is guaranteed for 25 years.
However, you’ll probably find that cavity wall insulation will last considerably longer than this.
What Materials Are Used for Cavity Wall Insulation?
Below are some examples of the most commonly used materials for cavity wall insulation projects:
Mineral Wool Fibre - Mineral wool fibre is made from molten glass, slag or stone. Which is melted down and then spun into fibres, this can then be injected into the cavity to be used for the cavity wall insulation. Mineral wool slabs are used in a cavity that requires a full or partial fill.
PIR - PIR (Polyisocyanurate) is a thermoset plastic used as rigid thermal insulation. These boards are used in a cavity wall that requires a partial fill.
Phenolic - Phenolic boards are manufactured by a process in which a plastic foam forms an insulating core between two flexible tissue faced layers. It has a high closed cell content and fine cell structure. These boards can also be used in a cavity wall that requires a partial fill.
How Can I Tell if my Home has a Cavity Wall?
There are three ways you can look to see if your home has cavity wall insulation.
The first method is to check the age of your home. If it was built before 1930 then it is unlikely to have cavity walls. Homes built between 1930 and 1980 will probably have been built with cavity walls. Finally, houses built after 1980 are more highly likely to have cavity walls.
The second method is to look at your brickwork. If your bricks are all laid lengthways then you probably have a cavity wall. If there are full-length and half-length bricks then you probably have a solid wall.
The third method is to measure your outside walls from a window or door. If the wall is more than 30cm in thickness, then you probably have a cavity wall. Anything thinner than 30cm means you have probably got a solid wall.
When you ask a professional cavity wall insulation company for a quote they will visit your premises and tell you what type of wall you have in your home.
How can I tell if Cavity Wall Insulation is already Installed?
If you can see the bricks on the outside of your home have a look to see if there are any covered up small holes. This is where the insulation was blown in.
If a company that supplied a guarantee did the work, then you should have been given this paperwork when you purchased your property. If it does have a guarantee but the paperwork is lost, you can obtain a new copy from GIGA for a payment of £25.
Another way to tell is to do a drill test. A professional installer can come and do this for you. By drilling a small hole in your brickwork, you will be able to see whether or not any insulation has been installed.
Can Cavity Wall Insulation Become Damp?
Cavity wall insulation is water repellent and therefore it shouldn’t get damp. However, some properties, if they are prone to rain driven by the wind and have damp problems, won’t be suitable for cavity wall insulation. It will be necessary to clear up the damp problems in the home before having this form of insulation installed.
How Much Does Cavity Wall Insulation Cost?
The costs of insulating cavity walls can depend greatly on the size of your home and the materials and time required.
Do I Need Planning Permission for Cavity Wall Insulation?
Planning permission isn’t usually needed for cavity wall insulation. The only time you will have to consult the planning department is if the insulation will change the appearance of the outside of your home, or you live in a listed building or within a conservation area.
How Do I Choose a Cavity Wall Installer?
Make sure your installer offers a 25-year guarantee with the Cavity Insulation Guarantee Agency (CIGA). The company should also be registered with either The National Insulation Association UK (NIA) or the BBA (British Board of Agrement) Each association has a code of professional practice.
You can look for an installer online at CIGA or NIA or at consumer sites like Which? Or you can look closer to home by googling cavity wall installers plus your location.
Can you get a grant for Cavity Wall Insulation?
There aren’t any grants for cavity wall insulation available, but your energy provider might offer you free installation subject to certain criteria. Contact E-On, Npower, EDF or SSE.
Can You Take Out Cavity Wall Insulation?
Yes. It is possible to take out cavity wall insulation. If the insulation is made up of mineral fibre it can be sucked out by using a powerful vacuum. Other types of insulation need to be broken down first. This is done by removing some brickwork, breaking the insulation down with special machinery and then sucking it out until it is completely clear.