Households in Amsterdam are being urged to hang their curtains outside their windows as health experts recommend simple hacks to moderate the heatwave rolling across the Netherlands, where homes were built for old-fashioned damp and coldish northern European weather.
In a viral social media post last week, Eline Coolen, the heat coordinator at the city’s public health institute, urged sweaty city-dwellers to rig up temporary curtain rails or drape curtains or sheets outside to stop the sun’s rays reaching their large windows.
The government, meanwhile, has activated a national heatwave plan, with advice on caring for elderly and vulnerable people, and researchers are trialling everything from fake trees to shadow art to cool down pavements and pedestrians.
“In Dutch houses, but also in many houses in northern Europe, you have very big windows,” said Coolen. “We have always built for the winter, when you want as much sun and warmth in your house as possible.
“But every year in Amsterdam alone, 110 people die because of the heat – and that could rise to as many as 600 in the future without serious measures.”
Inspired by the sheets that appear draped over windows in Amsterdam-Noord, where she lives, and a recent trip to Barcelona where people mounted blinds on their balconies, she urged people online to make DIY adjustments – because if you can stop the sun touching your windows, there will be less heat transfer into your house.
It’s a matter of physics, according to Bert Blocken, a professor of mechanical engineering at Heriot-Watt University, who believes in alternatives to energy-guzzling air conditioning.
“Most of the time we spend indoors, even on very beautiful, sunny days, because we’re working or we’re sleeping, when we also recover from heatwaves,” he said.
“We need to keep our buildings cool, ideally without active cooling devices. The climate adaptation of individual buildings is important but still today, many are built with large, glazed facades that generate a lot of heat.”
A huge body of research showed the best way to keep a building cool was simply to keep out the sun, he said. If architects considered a textile striped canopy ugly, there were modern, retractable outdoor blinds.
“The ancient Egyptians, Greeks and Romans did this tens of centuries ago, but sometimes we’re very good at forgetting lessons from the past,” Blocken said. “If I were mayor, my first executive order would be to apply exterior solar shading on all buildings.”
There are three levels of action, according to RIVM, the Netherlands’ national public health institute: behaviour, housing and urban design. Werner Hagens, coordinator of the Dutch heatwave plan, said new research had shown that simple awareness campaigns appeared to reduce deaths during heatwaves.
“You can make changes in the area, more green spaces, you can make changes in the building, like screens and maybe other cooling mechanisms, but you can also give perspectives on how people inside them can minimise heat,” he said. “These temperatures can form a risk for people in vulnerable health … and it reduces the risks.”
A study by the homeowner association Vereniging Eigen Huis found that 23% of people surveyed felt their homes were too hot in a heatwave, although four in five had tried to do what they could to cool them down.
Blocken said that while building owners could whitewash flat roofs and invest in outside blinds, greenery was key: not only green roofs and facades, but large parks, trees and green spaces.
Fake trees, pergolas covered with greenery and mobile “jungle blocks” can all help pedestrians stay cool and even slightly moderate temperatures, according to Jeroen Kluck, a professor of climate resilient cities at the Amsterdam University of Applied Sciences.
“There’s always a reason not to do it: there’s limited public space, there’s no more money,” he said. “But it makes the city more attractive, liveble on hot days and it increases biodiversity. If you make shadow, with a nice place to sit underneath and plants that can survive a bit of drought, it all helps.”
Sandra Phlippen, an economist and head of climate strategy at ABN Amro, said it made economic sense for local governments and businesses to invest. “One night of sleep loss [costs] close to €200 [£173],” she said.
“Imagine a street where there are 100 people living, everybody sleeps terribly for three nights because of a heatwave and the next day they’re unproductive. That’s your investment in trees for the whole year.”