The Department for Business, Energy & Industrial Strategy (BEIS) has published an interesting report into the prospect of using waterproofing products to allow cavity wall insulation to be installed in properties in areas exposed to wind driven rain.

The report is based on a study by Building Research Establishment (BRE) and University College London (UCL) and included tests on moisture ingress and thermal performance, which ultimately concluded that:

“Waterproofing treatments in combination with cavity wall insulation appeared to have the most notable beneficial effect.”

That is not what makes the report so interesting!

The report illustrates that external waterproofing products including Silane/Siloxane creams worked extremely well at reducing the absorption of water into the brickwork. This won’t come as a surprise to many PCA members, who have been applying products such as these for a number of years to help prevent walls suffering from damp issues.

But perhaps the more interesting part of the report is that it shows that there was “no evidence from the testing that waterproofing treatments assessed ‘trap’ moisture within the wall.”

This has often been the argument of critics of these products, but this report shows that there is no real downside to these products and that they let the wall dry as quickly as it would without the product.

Did the results show anything else of note?

The results showed that the use of just a waterproofing product only provided marginal improvement to the performance of uninsulated walls and, “cannot be considered as an energy efficiency measure in their own right.”

It is also clear from the report that the condition of the wall prior to application is of huge significance to the performance. The report then goes on to place great weight on the requirement to have a rigorous survey prior to any treatment.

It is important to note however, that the results are based on laboratory results alone and that real world data and testing was not possible.

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