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Problems of Cavity Wall Insulation

Cavity wall insulation does have tremendous benefits to your property...if done correctly. Unfortunately, as much as there are benefits, there are now an increasing amount of properties suffering the effects of poorly installed cavity wall insulation. 

The principal reason...the ‘Gold Rush’ of well-meaning, but flawed energy-saving insulation campaigns that meant many properties were checked poorly for suitability, while installation was rushed to meet demand and volume.

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Firstly, cavity wall insulation can be good, but...

Firstly, we would like to be clear that at the Property Care Association, we are pleased to see that there has been a continuous Government effort to reduce our carbon emissions while improving the quality of our UK homes and helping homeowners save valuable cash on their energy bills. Undoubtedly these are admirable and worthy causes.

We just do not want homeowners to suffer the same property issues as others have experienced, as a direct result of previous well-meaning, but flawed cavity wall insulation.

Cavity wall insulation graphic - PCA

Cavity walls and why you can have problems after installing insulation

Quite simply, cavity walls exist for good reason and that is to provide a barrier against rainwater penetration. The problem is that a great many of these cavity voids are either simply unsuitable for cavity wall insulation, or unqualified specialists have overpacked the cavity with insulation resulting in rainwater travelling through the insulation and reaching the internal wall. Thus creating problems with penetrating damp, mould, condensation and rot.

Why has this been allowed to happen?

Cavity wall insulation has been a subject that successive Governments over the past 30 years have attempted to promote. Previous Government drives such as ‘Eco’ & ‘Warmfront’ have made it readily apparent that in a large number of homes, instead of creating energy saving conditions, the process instead locked dampness and humidity into many homes. This lead to potentially expensive damp and rot repairs and in some cases, structural problems.

To add to the problem, sadly there have been retrofit insulation installers that may not have had the best of intentions, but these Government backed subsidies have always attracted a number of suppliers who are not sufficiently skilled. On top of that, as skilled as a retrofit insulation specialist might be, they do not necessarily have the skills and knowledge to identify the potential ‘ripple effects’ from the work they are doing.

What checks should I do before saying YES to cavity wall insulation?


The simple fact is that insulation installers will not have the level of expertise and knowledge of other property related issues that can be caused off the back of poorly installed insulation such as how to spot and fix problems failures found with cavity wall ties prior to installation and how to prevent problems of dampness occuring.

Even with the cost of the insulation being subsidised in many cases by the government, if something does turn out to be ‘not quite right’ after installation, that cost of remedial repairs will be more expensive by the presence of the insulation. Our advice…it’s not worth the risk or cost – get it checked properly!

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A precautionary list of checks you can do

Below is a list of precautionary checks you can take to identify if you will actually benefit from any retrofit action, or if you are inviting trouble into your property.

Cavity Wall Insulation Checks

  • Do you actually have cavity walls?
  • Are the walls (outside and inside leaf) structurally sound and free from cracks
  • Pointing, rendering brickwork is in good condition
  • Are gutterings and rainwater pipes in good condition and no leaks
  • Is the cavity at least 50mm wide and free of obstructions and debris

Solid Wall Insulation Check - Property Care Association

When problems occur with cavity wall insulation

When retrofit cavity wall insulation is installed into a property that is located or built in a way that means it should not have the cavities filled, or if the work is undertaken incorrectly, the first and most obvious sign of a problem is almost always internal dampness.

Most homeowners will be blissfully unaware if cavity wall insulation has not been installed correctly.  You will not know if it is over-packed, under filled, where it has slumped, where areas have been missed, vents have been blocked or obstructions missed.  Its simply very difficult to see obvious signs of any defect. Those that are aware of a problem with the cavity wall insulation within the walls will almost certainly have been put on notice with the appearance of dampness within their home.

On occasion, the use of cavity wall fills should have been a part of a suite of measures to improve thermal performance.  However, all too often it’s the only measure that’s been utilised.  Where cavities are discontinuous or are crossed by solid elements such as floor slabs, or parapets, “cold bridges” can be left.  Before the insulation was installed the temperature difference between these bridges and the wall may have been relatively small.  After the cavities within the walls are filled with insulation these un-insulated elements may be significantly colder than the surrounding walls.  This coupled with the effects of a draughty house, can create the right conditions for condensation and mould, often where it’s not been seen before.

We have also seen a growing number of properties where no defects exist with the building or the new insulation, but owners are reporting new problems with damp. In these instances, it has been found that the insulation has successfully stopped both warm air and moisture escaping. Without reintroducing air exchange through controlled ventilation the wet air has nowhere to go. Subsequently the humidity levels rise and mould growth is almost inevitable.

Pre-installation or condition surveys

If you have performed some of the suggested checks above and feel you may have a cause for concern or would just like to seek a professional opinion, then you can always contact one of our independent, Government-backed and TrustMark accredited PCA members who would be happy to conduct the necessary checks for you. Simply run a search using the member search function below and find a PCA member local to you!

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