When the heat in his apartment became too much to bear, software developer Zak (24), took a radical step: he decided to cover over the velux windows with reflective foil, blocking out the relentless rays of the sun.
“I live on the top floor. It’s just under the roof, and on some days the heat is unbearable,” he said. “There are four windows in the roof.”
Excessive heat in homes, offices and public buildings has prompted a debate in France this summer about the excessive use of glass in building design, which is being increasingly seen as impractical as global warming drives up summer temperatures.
Videos explaining how to cover windows with reflective foil emergency blankets or paint the glass with Meudon white powder – quick methods to block out heat and glare – have gone viral on social media with many commenters describing their efforts.
“We are dying of the heat, there are floor-to-ceiling windows on every floor,” Adrien (49), an office worker in La Défense business district of France told news agency Agence France-Presse, which reported this week that excessive glass in office buildings was driving more people to work from home.
“One colleague cracked, she said her phone blacked out because of the heat.”
At least 200 schools in France were forced to close in June as temperatures hit 38 degrees in a heatwave that struck right as many students were sitting end-of-year exams. Teacher unions pointed to poorly-designed buildings and bare concrete playgrounds that act as heat traps.
France recorded 3,700 heat-related deaths in 2024, with 17,000 people seeking emergency care. Once rare in France, temperatures of 40 degrees are becoming increasingly common, and the area affected has spread north.
Nevertheless, there are signs that building practices are not adapting fast enough.
The shiny new Nantes train station was built at a cost of €37.5 million and launched in 2020 with much fanfare over the panoramic views from its glass-walled, glass-ceilinged upper floor.
It was forced to close to the public this summer as internal temperatures reached dangerous levels. It reopened after industrial-size fans were placed inside, but internal temperatures still measured 32 degrees on a day when it was 26 degrees outside, according to a test by broadcaster Franceinfo.
[ Extreme heat breaks temperature records across EuropeOpens in new window ]
“I started to hyperventilate, and then I couldn’t stand up any more,” said Margaux Perré, a shop worker in the station who was overcome by heat in the lift – even after the fans were installed. “It looks nice, but it’s not practical. It wasn’t well thought through.”
The architect has defended his design to French media, while rail operator SNCF has said the station will be assessed for adaptations to climate change.
For Pascal Lenormand, an expert in building energy design, it’s an example of a “tomato greenhouse”, a modern style of building he has taken to calling out on social media with the hashtag “#balancetonfour”. It means “denounce your oven”, a play on the French for “#MeToo”.
“They’re pretty much all designed with a concrete heart, and an outside skin made of metal and glass. It is very standardised,” he said. “The problem is every square metre of glass means more energy let into the building. We spend a lot of money making big windows, and then we spend a lot of money correcting the drawbacks of big windows.”
The trend of glass-fronted buildings emerged at a time when energy was cheap, and they rely on energy-intensive air conditioning and heating systems to maintain a liveable internal temperature, according to Lenormand.
“If you live in a building which cannot work without air conditioning, it is very quickly dramatic,” if for any reason the air conditioning switches off, Lenormand said, something that has happened in France when systems are overwhelmed by demand.
Electricity prices more than doubled during a heatwave this summer as demand for air conditioning surged, according to a report by energy think tank Ember. The heat simultaneously forced 17 of France’s 18 nuclear power plants to partly or fully shut down, as they were unable to sufficiently cool their systems.
A wide-scale roll-out of more air conditioning – an idea proposed by far-right leader Marine Le Pen – is not a good solution, according to a report by non-profit Foundation for Housing for the Disadvantaged. It noted that air conditioning units already account for about 5 per cent of France’s carbon emissions, run on highly polluting refrigerant gases, and pump hot air out on to the street.
Their widespread adoption would increase the overall temperature of Paris by 2 degrees and by as much as 3.6 degrees during heatwaves, according to Ademe, the French public agency for the ecological transition.
Several political parties have called for public subsidies to retrofit houses with climate-friendly alternatives to air conditioning, such as geothermal cooling and solar shades.
“I’m also quite angry, because in my job, with many buildings it’s very easy to see from the very first drawing that we will have overheating problems,” Lenormand said.
In response to his social media posts, employees on building projects have privately messaged him to say heat problems have become evident during construction, but they feel they can’t speak out.
“I cannot accept to see such buildings being built,” he said. “When they are being built it’s too late, we should have already said ‘stop’.”