Office-To-Residential Conversions Can’t Cope With U.K. Heat Wave

As in many other cities around the world, office-to-residential conversions have become popular in the UK since the pandemic, as employees have continued to work at least part of the time from home and developers have snapped up vacant office buildings. But the insurance company Zurich UK notes that these repurposed units are also vulnerable to high temperatures: Glass curtain walls and floor-to-ceiling windows popular for office buildings are notably poor at keeping out heat, and can create kiln-like conditions in interiors.

Planning figures show that between 2020 and 2021 alone, the number of applications made to British authorities for such office-to-apartment conversions leaped by 20%, and more than 73,500 homes have been carved from former office blocks since 2015. The trend predates the pandemic, driven in part by a widespread lack of affordable housing in costly cities such as London and Manchester. But commercial buildings can be difficult to adapt to residential use. Independent research published by the UK government in 2020 found that these retrofitted structures offered worse conditions than purpose-built equivalents, with plumbing systems that can’t handle domestic volumes of water use and a lack of internal light and ventilation being common problems.

As Britain’s summers heat up, these problems could be felt more acutely, leaving the country with a housing stock ill-suited to a dangerously warmed climate. With much office space designed to rely on artificial lighting even in daylight, former office buildings are often built without internal courtyards or lightwells. This means they replicate a problem found across many recently built UK apartments — single-aspect windows only on exterior walls that make cross-ventilation impossible. The locations of former office buildings can also be problematic. Unlike purpose-built residential housing, they tend to be sited in heavily developed commercial areas, which suffer more from the urban heat island effect.

While overheated conditions can be found in large high-end conversions, the studio flats built in 1960s-era office complexes around Britain’s cities that accommodate poorer renters — buildings that have already been accused of “human warehousing” — are seen as particularly vulnerable.

Extreme heat has not until very recently been a cause of great concern in British construction, with homebuilders typically focusing more on keeping warmth in than on keeping it out. Common domestic building materials — traditionally brick, more recently concrete covered with brick veneer — tend to be highly heat-absorbent. Many homes lack air conditioning, and windows are by preference large and unshaded to combat the country’s frequent winter gloom. Such characteristic are well suited to the region’s historically mild summers, but not the periods of increasingly fierce seasonal heat that, thanks to climate change, the UK has now entered.

This needn’t mean that, in order for the UK to become heat-resilient, office conversions must end — not least because Britain has an acute need for more affordable homes. “Developers need to ensure that retrofitted buildings are designed with increased ventilation and shading to keep temperatures down,” said Zurich’s major loss property claims manager, Paul Redington, in a statement released to CityLab. “Building more affordable housing is a priority but we must avoid creating swathes of homes unfit for a rapidly warming world.”

To improve the heat performance of converted buildings, developers can add adaptations such as brises-soleils or extra ventilation shafts; tree planting, traffic reductions and other resilience features can combat urban heat islands in ex-office districts. But as this week’s record temperatures show, the UK is entering uncharted territory when it comes to summertime heat — and its infrastructure will need to follow.

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