The Hidden Cost of Failing Cavity Wall Insulation
Cavity wall insulation (CWI) was once seen as a simple solution to Britain’s leaky homes. But as the BBC has just reported last week, it is becoming clear that for many households, it has instead brought damp, mould, and mounting repair costs.
The government admits that at least 30,000 homes have failed CWI. Yet studies suggest the true number could be far higher, with one survey in Northern Ireland finding that only 37% of homes inspected were defect-free (Northern Ireland Housing Executive Survey, 2019). With more than 15 million UK homes fitted with CWI, the scale of the problem is still largely unknown, and that uncertainty leaves thousands of families vulnerable.
Thermal scans revealing cavity wall insulation defects (The Telegraph, 2015)
What makes this crisis especially damaging is its invisibility. Problems often remain hidden until mould spreads across walls or health begins to suffer. Families report worsening asthma and respiratory illnesses, alongside the stress and financial strain of trying to repair homes that were meant to be warmer and cheaper to heat.
That is why in-depth diagnostics are essential. Without reliable, affordable tools to identify which homes have defective insulation, councils and homeowners alike are forced to act reactively and only realise the extent of the problem when it becomes unmanageable. Our own research into new detection methods is focused on making these failures visible before they escalate, so support can reach the households that need it most.
This is not just about energy efficiency. It is about protecting health, preserving the value of homes, and ensuring that the promise of warmer living does not come at the expense of safety. The challenge now is to quantify the true scale of failed CWI, with precision and care, before more families pay the hidden price.
Sources :
BBC News (2025). ‘We were sold insulation – now our homes are full of damp.’ BBC News, 4 September. Available at: https://www.bbc.com/news/articles/c8606gp4711o
Howell, J. (2015). Cavity-wall insulation crisis may hit three million homes. The Telegraph, 21 March. Available at: https://www.telegraph.co.uk/finance/property/11485758/Cavity-wall-insulation-crisis-may-hit-three-million-homes.html
Northern Ireland Housing Executive (2019). Cavity Wall Insulation Research Project. Belfast: NIHE. Available at: https://www.nihe.gov.uk/working-with-us/research/cavity-wall-insulation-research-project-2019