The number of UK homes overheating in summer quadrupled to 80% over the past decade, according to a study, with experts calling the situation a crisis.
Heat already kills thousands of people each year in the UK and the toll will rise as the climate crisis intensifies. Urgent action is needed both to inform people on how to cope with high temperatures and to adapt homes, which are largely designed to keep heat in during the winter, the researchers said.
The study also found that the use of air conditioning soared sevenfold to 21% of homes between 2011 and 2022. The researchers warned that continuation of this trend could put strain on the national electricity grid, increase carbon emissions and fuel social disadvantage among families unable to afford air conditioning.
The research was prompted by extreme heatwaves in 2022, when temperatures in the UK rose above 40C for the first time. The past two years have been the hottest on record globally, driven by the burning of fossil fuels, which shows no sign of slowing down. More than 10,000 people have died as a result of summer heatwaves from 2020 to 2024, data from the UK Health Security Agency shows.
The huge rise in overheated homes and air conditioner use was “a shocking result”, said Dr Mehri Khosravi, at the University of East London, who led the study: “Over the heatwaves experienced in 2022 we had nearly 4,500 dead, but this excess mortality is hidden.” Many heatwave deaths are due to heart attacks, strokes, and respiratory and kidney problems, exacerbated by high temperatures.
“British people are not familiar with heat and often don’t see heat as a risk – most consider it as something nice, for socialising, going out, going to the beach” said Khosravi. “Staying inside, drinking less alcohol, and not being on the beach [can help cope with extreme heat]. But these are cultural things we are not familiar with.”
Bob Ward, the chair of the London Climate Ready Partnership, said: “This study highlights the extent of the risks caused by overheating of buildings in the UK, which kills hundreds of vulnerable people every year and costs the economy millions of pounds in lost productivity.”
“Successive governments have failed to treat this issue with the seriousness it needs and we now face a crisis,” he said. The UK’s climate adaptation plan, published in 2023 under the previous Conservative government, was condemned as “very weak” on dealing with rising heatwaves.
The study was published in the journal Energy Research & Social Science. It asked almost 1,600 households whether they had experienced uncomfortable warmth in one or more rooms during the summer of 2022, the same question that had been asked in 2011.
It found the rate of overheating reported leaped from 18% to 80% in 2022. More than a third of households said their homes had overheated daily and a further 19% said this happened five or six days a week.
Half of people reported experiencing poor sleep because of heat, while a quarter said they suffered frequent headaches, fatigue and had to work less. Half also said they had little to no knowledge of how to cope with extreme heat, with another study finding that a third of people still do not consider heatwaves an immediate risk. Most people in the survey tried to cool themselves in some way, with lighter clothes, cold drinks and cool showers among the most common actions.
Similar high levels of overheating were reported from all types of home, from flats to detached houses. However, homes built after 1900 were twice as likely to report overheating, as were those with the highest energy efficiency ratings, EPC bands A and B. Modern buildings focus on airtightness and insulation to cut heat loss in winter, said Khosravi, which can worsen overheating without good ventilation.
However, she said: “Research shows that adapting building design is not enough – we also need to adapt people’s behaviour. A simple example is that in the UK, when the weather gets hot, the first thing many do is open the windows. But that only invites more heat to our houses.”
Overheating was highest in London, the south-east and the north-west and lowest in the north-east, Wales and Scotland. Lower income households were more than twice as likely to report overheating than high-income ones, probably because renters cannot make changes to their homes and air conditioning is costly.
Building design regulations were updated in 2021 to consider passive cooling options, such as shading and window shutters. But this applies only to newly built homes and no research has been done to see if the changes have had any effect.
“Many policymakers don’t even believe that overheating risk exists,” Khosravi said. “One said to me: ‘We only have one month of summer. Why do we need to focus on that, when we have 11 months of cold weather?’” The UK had one of the highest rates of heat-related deaths in Europe in 2022.
Communication with the UK public about overheating is inadequate, she said. “The only warning system is based on colour but it doesn’t explain what red, amber, yellow warming means, or what people need to do.” Khosravi now aims to research how to improve such communication.
Ward said: “The government should carry out an urgent retrofit programme to improve ventilation and passive cooling in homes, so that we do not become dependent on expensive air conditioning. This should be targeted at those people who are most vulnerable and whose homes are most likely to overheat in London and south-east England, which tends to experience the hottest temperatures.”
