In 2022, a report examined just how susceptible UK houses are to overheating. Commissioned by the Climate Change Committee (CCC), a public body that advises the UK government, the report found that 55 percent of UK homes already have bedrooms that overheat in hot weather. In a world heated by 2 degrees Celsius, the modeling projected that every home outside of Scotland would have unacceptably warm bedrooms, and 17 percent of homes—mostly in London—would have living areas and bedrooms that were too warm. If the world warmed by 4 degrees Celsius, every single home would meet criteria for overheating. With current policies and action, the planet is currently heading toward around 2.7 degrees Celsius of warming.
“The most at-risk buildings and homes tend to be smaller,” says Michael Edwards, a director at the architectural firm Arup, which wrote the CCC report. Stopping overheating in all UK homes in the current climate would cost £250 billion ($319 billion) in building upgrades, although Edwards points out that an efficient way to spread the cost would be to upgrade the buildings while other changes were being made.
It’s a hefty total, but the anti-heat interventions needed are surprisingly modest. Fitting houses with external shutters and windows that block intense sunlight would be a good start. “The idea is to stop radiation, rather than dealing with it once it comes inside,” says Mavrogianni. External window shutters are common in Mediterranean countries like Spain, Italy, and Greece, which are used to dealing with intense summers. Shutters are even more effective when combined with fully openable windows—which is another thing that’s often lacking in London homes. Fitting residences with shutters, light-blocking windows, roof insulation, and ceiling fans would eliminate overheating everywhere except London, which would still have some overheating, according to the Arup report.
Air conditioning could help—but only as a last resort. Only around 5 percent of UK houses have air conditioning, and even Mediterranean homes are much less likely to have air conditioners than the average US home. In the Arup modeling, air conditioners would be needed in 22 percent of homes to cope with overheating in the 2 degrees of warming scenario. This comes with downsides. Air conditioners use a lot of energy, and they’re vulnerable to power failures—compounding problems in worst-case scenarios if electricity grids fail. “It’s important that we prioritize the passive cooling strategies,” says Mavrogianni.
Building regulations are also catching up with the risk of overheating. In 2021, the UK government updated guidelines for new homes in England. The update states that buildings should be constructed in a way that minimizes unwanted excess sunlight in the summer and allows easy ways to get rid of heat. It also sets maximum limits for window sizes as a proportion of floor space. Small apartments, in essence, should have smaller windows—unless there is particularly good ventilation.
Retrofitting buildings isn’t the only way to deal with heat. We can make urban spaces cooler by planting more trees, creating green spaces, and building shade structures. London has a cool spaces map that points out places in the city with below-average temperatures, as well as water fountains and indoor cool spaces where people can take refuge from the heat. Mavrogianni points out that a lot of knowledge about dealing with high temperatures is strongly linked to culture.
