Some of the UK’s more energy-efficient homes could face greater long-term exposure to flooding and subsidence than less efficient properties, according to analysis from residential property data firm TwentyCi.

The company said its latest figures suggest homes with EPC ratings of A – C are, collectively, more likely to face high flood and subsidence risk than properties rated D – G.

TwentyCi said this points to a potential gap in how environmental risk is assessed across the housing market, particularly where energy performance is treated as a proxy for wider resilience.

FLOOD AND SUBSIDENCE EXPOSURE

The UK housing stock remains concentrated in the middle of the EPC scale, with 37% of properties rated D and 35% rated C. However, TwentyCi said a comparison with physical risk indicators presents a more complicated picture.

It found that EPC G-rated homes are currently the most exposed to flood risk, with 5.65% classed as high risk, rising to 6.94% by 2055. But B-rated homes were found to have the second-highest flood exposure, with 5.27% currently at high risk and 6.52% projected by 2055. TwentyCi said this would amount to more than two million properties nationally.

For subsidence, B-rated properties were identified as the most exposed. TwentyCi said 6.74% are currently at risk, with that figure projected to rise to 23.29% by 2055, affecting an estimated 7.4 million homes.

By contrast, coastal erosion risk was found to track more closely with EPC distribution, with G-rated homes showing the greatest exposure at 0.09%, followed by F-rated properties at 0.04%. TwentyCi said that although the numbers are smaller, the consequences can be severe because of the potential for total property loss.

UNDERWRITING QUESTIONS

The findings are likely to be of interest to lenders and other housing market professionals weighing energy performance data against longer-term climate resilience.

Colin Bradshaw, chief executive at TwentyCi, said: “While Energy Performance Certificate (EPC) ratings remain a critical tool in assessing mortgage suitability, analysis of UK residential property data shows they do not reliably indicate exposure to key environmental risks such as flooding and ground instability,

“In fact, some of the UK’s most energy-efficient homes are also among the most vulnerable to flooding and subsidence.

“For lenders, that creates a potential blind spot in portfolio risk. To build truly resilient mortgage books, lenders need to assess energy efficiency alongside a broader range of environmental risk factors.

“As climate pressures intensify, the data underscores the need for a more holistic approach to mortgage underwriting. Relying solely on EPC ratings could leave lenders exposed to hidden risks, particularly within segments of the housing market traditionally considered ‘safe’.”