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By Olivia Rudgard
The cooler parts of the northern hemisphere are getting hotter. Europe is the world’s fastest-warming continent, and Canada is warming twice as fast as the rest of the world — a trend driven by both regions’ northernmost extremes. That means millions of people live in homes built for weather that no longer exists.
The implications could be deadly, particularly for people who spend a lot of time indoors, in spaces they’re unaccustomed to keeping cool. Europeans and North Americans, for example, spend about 90% of their time inside. While more air conditioning will help — just 10% of Europeans have it at home — AC also adds carbon emissions and strains power grids.
That leaves organic solutions, like those common in places with experience building for extreme heat. “We can definitely learn lessons from countries that have been facing hot summers for several years,” says Giorgos Petrou, a research fellow in building physics and urban modeling at University College London.
Of course, it’s not feasible to simply import Morocco’s iconic courtyards or Seville’s narrow streets to northern climes. But it is possible to incorporate elements of those concepts. As summer heat waves bake cities from Boston to Berlin, here are four ideas for adaptive design.
The Moroccan riad
The heat caused by direct sunlight on walls and windows is known as “solar gain,” a label that can feel misleadingly upbeat during periods of high temperatures. To minimize solar gain and keep a space cool, southern European towns and cities have small, windy streets that maximize breeze and shade. In places such as China, India and north Africa, courtyards are also used to create enclosed, cool areas.
Adding water accentuates this effect. In Morocco, riads incorporate a fountain or pool in a central courtyard, which cools the surrounding building. It’s not just for ambiance: In a climate where temperatures routinely reach 40C (104F) in the summer, courtyards are also crucial for safety. Studies have shown that the riad design creates a more comfortable microclimate due to the circulation of air over water and the use of shade and greenery.
The Moroccan riad design creates a cooler microclimate. Photographer: Juliette Robert/Haytham-REA/Redux
Mopping floors and wetting outdoor patio areas likewise promotes cooling, says British TV presenter and designer Kevin McCloud. At his own home, McCloud is adding an outdoor pond with vents beside it that capture cool air and send it into the house. A clay pot filled with water and left on a windowsill can have a similar effect.
The shuttered Spanish villa
The best method for keeping a building cool is to stop heat from reaching it in the first place, says Anna Mavrogianni, a professor of sustainable, healthy and equitable built environment at the Institute for Environmental Design and Engineering at UCL. “External shading, such as shutters or overhangs, are generally found to be more effective than internal shading,” she says.
Petrou says external shutters are “a common feature in hot countries [on] pretty much every home.” One of his studies found that London could reduce summer heat mortality by at least 38% with external shutters. Hotter countries also use awnings and balconies to block sunlight, and walls and roofs painted in light colors to reduce heat absorption.
Experts say external shading, such as shutters, are more effective than internal shading. Photographer: Starcevic/Getty Images
Shutters aren’t always possible to install, especially if windows are particularly large or open outwards. In that case, blinds and curtains are the next best thing. Shading for large windows has long been in demand to keep homes warm in winter, says Amy Joyce, a senior marketing executive at UK-based Appeal Home Shading, but nowadays customers are also looking for cooling in the summer.
“With the older houses, it’s keeping heat in, but with these new builds, they are so well-made and so well-insulated it’s [about] trying to keep things cool,” she says. “Especially with people working from home — a lot of home offices, reducing temperatures in those has become huge.”
The Iranian windcatcher
There are a number of traditional methods for using natural air movement to send cool air into warm spaces. In the Middle East, wind catchers — towers that incorporate a gap or “wind scoop” to suck in cool air — are often combined with water to create a more powerful cooling effect.
In European homes, problems often arise when all the windows point in one direction and roofs and walls are tightly insulated. Without building a wind tower, homeowners can create similar airflow in a low-impact way by being judicious with window and doors. “Closing the windows during peak external temperatures and opening them later in the day when it’s cooler, and enabling cross ventilation if possible” can help reduce indoor temperatures, says Mavrogianni.
Wind towers on Amir Chakhmaq Square in the old town of Yazd, Iran. Photographer: Leisa Tyler/LightRocket
The Ivy-covered Italian house
It only takes one barefoot step on a driveway in summer to know just how hot tarmac can get. By contrast, keeping an area green limits the most extreme heat through both shade and evapotranspiration — the process by which water drawn from a plant’s roots evaporates into the air and cools the surrounding area.
This also reduces the “urban heat island” effect, in which buildings and other infrastructure cause cities to warm more than rural areas. One 2004 study of a Toronto neighborhood found that trees could reduce annual energy use by 30%. AC, on the other hand, contributes to the urban heat island effect, dumping hot air outside buildings as it cools the inside.
Ivy is among the best climbing plants for cooling. Photographer: Vladimir Mironov/Getty Images
In the Mediterranean, shade trees and climbing plants like wisteria are frequently used to cool down buildings. Research carried out by the UK’s nonprofit Royal Horticultural Society suggests that ivy is the best plant for cooling, though all types of climbing plants will do the trick.
Such plants can help keep a building warm in winter, too, says Tijana Blanusa, principal horticultural scientist at the RHS. “When you have this layer of natural insulation around the building,” she says, “in summers you have cooling of the building, and in winters you have insulation.”
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