The rapid growth in office-to-residential conversions has prompted fresh warnings that thousands of homes could face overheating risks unless climate resilience is built into future developments according to Zurich UK.

Zurich UK found that applications to convert commercial buildings into homes increased by 58% between 2022 and 2025, rising from 1,025 to 1,623. Since planning rules were relaxed in 2021, more than 103,000 former commercial buildings have been converted into residential properties across England.

The insurer said the surge comes as the UK experiences increasingly frequent periods of extreme heat, with May 2026 recorded as the warmest May since 1922. Concerns have been raised that many office buildings were never designed for residential occupation, with features such as sealed windows, large glazed façades and limited ventilation increasing the risk of overheating.

Megan Dunford, Head of Large & Complex Property Claims at Zurich UK, said: “Commercial buildings are generally designed to different operating tolerances than residential properties, and sustained temperature variation can place material stress on the building fabric.

“This increases the risk of thermal expansion and contraction, which may contribute to cracking, subsidence and ultimately escape of water incidents. Over time, this not only undermines building safety and durability, but also exposes residents to higher maintenance costs and reduced living standards.”

The warning comes as the Government pushes ahead with plans to deliver 1.5 million new homes during the current Parliament, with office-to-residential conversions expected to continue playing an important role in boosting housing supply.

Zurich said developers should consider measures such as improved ventilation, solar shading and overheating assessments to ensure converted buildings remain fit for purpose as temperatures continue to rise.