Removing Cavity Wall Insulation

Cavity wall insulation can be done incorrectly

When installed correctly, cavity wall insulation is a fantastic way to help lower your energy bills. The insulation will slow the movement of heat across the wall and therefore your home will stay warm longer once you put your heating on, meaning you need to use less energy to keep your home at a comfortable temperature. It is for this reason the Government have traditionally been keen to promote the measure – after loft insulation, cavity wall insulation is the second most cost-effective energy saving solution.

In some cases though, cavity wall insulation simply isn’t the answer – the good news is that it can be rectified, the bad news is that there is a cost.

Why would you remove cavity wall insulation?

In the 1980s, building regulations stipulated that insulation should be installed during the construction of new buildings. As soon as these regulations came into play, it became clear there were a huge number of slightly older properties that could also benefit from this type of insulation; however the only way to get the insulation into the cavity once the property was built was to inject it. Since the materials were cheap and the installation process was relatively simple, the Government really pushed the measure. Thousands of small installer companies popped up, knowing they could install the insulation in people’s homes and be well paid for the work.

As a result, any property with an unfilled cavity was targeted, regardless whether it was suitable or not – so obviously issues occurred. Some of these issues are laid out below:

1. The insulation material used was unsuitable – e.g. urea-formaldehyde. The problems with this insulating product were two-fold: Firstly, it breaks down, releasing (carcinogenic) formaldehyde into the home. Secondly, when the insulation breaks down it falls down the cavity, meaning walls higher up no longer benefit from the insulation.
2. When cavity walls were first introduced in the 1930s, the cavity’s sole purpose was to prevent water crossing the wall from outside to inside, causing damp in the home. As a result the early cavities were very thin – insulation could cause bridges between the two skins of brick, allowing water to cross and leading to damp issues in the home.
3. The insulation was installed incorrectly. When the cavity wall installer puts the cavity wall insulation in the gap between the two skins of brick, the wall needs to be drilled in various places to allow an even distribution of the insulation. If the distances between the drilled holes were incorrect, then the insulation would not meet leading to cold spots.
4. Another issue was corner-cutting. Since installers are paid per m2 of wall, they need to do the jobs as quick as possible. When beads are injected into the cavity wall they are injected with a uPVC glue which binds all the beads together. The problem is that doing this properly – injecting the glue with the beads – takes about 3 times longer than installing the beads alone. Some installers wouldn’t bother, as they were looking to maximise profits by doing multiple jobs in the same day. This often led to beads ‘settling’ in the bottom of the cavity, meaning there was no real insulating impact on the upper parts of the wall.
5. Until the development of new technology, cavity wall insulation wasn’t suitable for every property. If a wall is privy to driving rain for instance, the cavity is required to prevent ingress of water into the home. If these walls were retrofitted with old-fashioned types of cavity wall insulation, it could quickly lead to damp issues – this is most prevalent in coastal regions.
6. Another example of a wall being unsuitable is when we hear of timber frame properties having had cavity wall insulation installed. These properties should never have cavity wall insulation installed. However an untrained or untrustworthy installer may have installed anyway to make sure they get paid for the job. We get several phone calls a month from homes who are in this situation and are trying to sell their properties, but are finding it impossible since mortgage companies won’t allow prospective buyers to get a mortgage on the property until the cavity wall insulation is removed.
7. The final reason is when someone has just bought a property previously installed with cavity wall insulation. In some cases, the insulation causes allergies for the new homeowner and again this needs to be removed despite the energy savings resulting from the installed cavity wall insulation.

How to get rid of unwanted cavity wall insulation

If you can relate to any of the above, then it is relatively easy to get the offending cavity wall insulation removed – bricks at the bottom of the wall are removed and the insulation is simply sucked out, leaving the cavity completely clear.

The cost of getting cavity wall insulation removed is £21 – £22 / m² depending on the material that was used in the first place, therefore for a semi-detached (which is 80m²) the price will be approximately £1,680 + VAT @ 20%. For a bigger detached property (so roughly 120m²) the price to remove the cavity wall insulation would be a £2,520 + VAT @ 20%.