Cavity wall insulation removal - RetrofitSouthampton

“Wait!” I hear you say – “why would I remove something which is probably the most common form of energy saver?”

Indeed, retrofit cavity wall insulation is generally something that is encouraged for homeowners looking to improve the energy efficiency of their homes. So it may seem counterintuitive to remove insulation that was installed for energy-saving purposes. However there are circumstances where it can actually be beneficial.

The history of retrofit cavity wall insulation

Cavity Wall Insulation (CWI) was first introduced as part of building regulations back in the 80s. Insulation was added to the cavity as the walls were built. As many houses already existed with cavities but no insulation, it made sense that these cavities could be retrofitted with insulation . The process involved drilling holes in the brickwork and injecting insulation into the gaps.

Unfortunately, some homeowners have since suffered from some unexpected problems arising from cavity wall insulation. This was due to a government-backed scheme funded by tax on energy bills, aimed at reducing emissions and improving energy efficiency.

Many people were convinced to join the scheme by promises of lower bills from cold callers working for energy companies. However, in some cases, corners were cut and poorly installed insulation was used. Installers were paid based on the amount of wall they covered, leading to rushed jobs. In some case walls were only partially filled with large areas that had no filling and so caused cold spots, prone to getting damp when condensation forms.

The downsides of retrofit cavity wall insulation:

One concern is that cavity wall insulation has a the potential for reduced ventilation. Cavity walls are designed to allow airflow, which helps prevent the buildup of moisture. Houses built from the 80s onwards (with insulation added as the walls were built) could have an adequate air gap around the insulation, but when it is pumped into the cavity of an existing wall it is not possible to have this air gap. This can hinder natural ventilation and cause humidity to accumulate within the walls. Without proper ventilation, the risk of dampness and mold growth increases, which again can have detrimental effects on the overall health of the property.

Added to this is the fact that some forms of insulation act like a sponge and so retain the moisture which was caused by this lack of ventilation. If a house already had damp issues or is prone to damp issues due to factors such as wind blown rain, it is arguable that the insulation should not have been installed in the first place.

The insulation itself can degrade and drop. Again this leaves areas of the wall with no insulation and so cold spots form and cause condensation – yet more damp. If the insulation drops down around the damp proof course it can clog the cavity forming a bridge between the damp ground below the DPC and the supposedly dry bricks above, allowing moisture to seep into the bricks above the damp course.

See Case Studies https://retrofitsouthampton.org/case-studies/ventilation-damp/unblocking-wall-cavity/

More modern properties are designed specifically so that insulation can be fitted and have a wide gap between walls allowing for plenty of airflow, but many older properties built with cavity walls prior to the use of insulation may have a very small gap. which is unsuitable for filling due to the resulting lack of airflow.

If any of the following conditions apply, then blown in retrofit cavity insulation could cause problems and you may be entitled to compensation*

Your house is subject to severe windblown rain (see map below) and the insulation has got damp.
Walls are damp due to other reasons, e.g. water ingress due to roof/guttering.
The cavities are less than 50mm
The insulation has dropped, disintegrated, was installed in “clumps” rather than evenly spread.
Wall ties are damaged.
The exterior wall has cracks or otherwise compromised brickwork or render.

Wind blown rain map

The possible benefits of removing cavity wall insulation

We have no reason to think that these problems are anything other than a minority case and if you are not experiencing damp, condensation or mould please don’t rush out and get your CWI removed. But if you are concerned, it is worth getting an independent survey, as opposed to a survey carried out by a company who may have the incentive to “find” a problem where there isn’t and sell you either CWI extraction or other remedial works.

However If you do have issues that are caused by the poorly installed retrofit CWI, by removing the insulation, the walls can dry out properly, reducing the risk of further damage to the property and improving the overall living conditions. This can lead to a healthier and more comfortable environments.

Improved ventilation can also help regulate indoor temperatures, making the property more comfortable and potentially reducing the need for excessive heating or cooling.

Also, by removing failed retrofit cavity wall insulation, homeowners have the opportunity to re-install better products. Provided the walls are given time to dry out, there are other types of pumped insulation such as bonded beads which allow airflow around polystyrene beads. The beads do not drop forming potential cold spots because they bond together, however the downside is that these can never be removed without demolishing part of the wall.