Green facades, white roofs and wind towers: how megacities escape the heat

Green facades, white roofs and wind towers: how megacities escape the heat

In the era of global warming, surviving in the concrete jungle is not easy: concrete and asphalt heat up quickly, dense buildings interfere with the movement of air, and emissions from factories, cars and air conditioners exacerbate the situation. In megacities, there is a heat island effect – in the center it is 10–15 °C hotter than in the outskirts. But the townspeople do not give up and invent new means of combating the heat, often relying on ideas from the past. Nestled under a fan, “Subtlety” talks about modern architectural solutions, materials and technologies that help cool big cities.

1. Vertical gardens

The most obvious (and pleasant) way to protect the city from the heat is greening: by increasing the area of ​​u200bu200bcanopies by 10%, the ambient temperature can be reduced by 1.5 °C. Therefore, in big cities around the world, not only the usual parks and squares appear, but also vertical gardens on the roofs and facades of houses. Singapore was a pioneer: the concept of a garden city was developed here more than 50 years ago – first they planted trees on the streets, then they took up the landscaping of skyscrapers. In the 1970s, the roofs turned green in Germany; since the beginning of the 21st century, this idea has been implemented in France, the USA and Canada. London authorities have set aside as much as 93 hectares in the very center for rain gardens and vertical gardening, and in Madrid they plan to cover at least a quarter of the buildings with flowers and shrubs to cool the city by 8 ° C.

2. Albedo effect

One of the causes of urban heat is the many dark surfaces that accumulate heat and warm the air. To make it a little cooler, they resort to the albedo effect, which has long been known in southern countries – they use the most light materials that reflect sunlight. On a summer day, an ordinary white roof reflects 80% of the sun's rays, a gray one only 20%. And recently, American scientists have created an “ultra-white” paint based on barium sulfate, which reflects 98% of sunlight, cooling the surface by 4.5 °C.

In New York, 1 million square meters were covered with reflective paint. m of roofs, and in sultry Indian Ahmedabad, a mixture of white limestone and light paint was applied to 7,000 roofs in poor neighborhoods whose residents cannot afford air conditioning. The authorities of Rio de Janeiro intend to follow the same path: they plan to lighten all the roofs in the favelas, where there are almost no trees. In Los Angeles, dark asphalt was replaced with light gray, cooling the roads immediately by 10 ° C.

3. Wind in the city

Arab cities of the future use ancient technologies: in Masdar, which is being built in the middle of the desert, buildings are placed close to each other, roofs are placed at a special angle, and a 46-meter wind tower draws in cool air like a funnel and releases it onto the streets of the city. It works very cool: even if the desert has warmed up to +35 °C, it can be only +20 °C in Masdar! First Badgirs– wind towers – appeared in the Middle East 1000 years ago, but they were placed not on the streets, but in houses. Bagdir can be considered a prototype of an air conditioner: the tower ran through the center of the building, removing stale air from the room and drawing in clean and cool air. And, mind you, without any electricity!

German Stuttgart, surrounded by hills, is ventilated with the help of ventilation corridors – wide streets with trees that allow clean air to descend from the heights into the city. Buildings are prohibited in several areas so that houses do not interfere with the movement of air masses.

4. Dynamic facades

Another time-honored technique is shutters and grilles that cover houses from the sun. One of the ultra-modern skyscrapers in Abu Dhabi used the mashrabiya principle- a medieval carved lattice that lets light and air into the room, but not the burning rays of the sun. In its likeness, the Twin Towers have created a complex dynamic façade of hundreds of wooden hexagonal panels that open and close depending on where the sun is.

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5. Just add water

Artificial reservoirs and fountains have cooled cities since the Middle Ages, and today they are helped by a variety of water installations. Their use allows you to reduce the temperature by an average of 1.5 ° C, and if there is a lake or river nearby, by as much as 10 ° C. Special frames with water sprayers can be seen in parks and on the streets of many European cities. In China's hot Chongqing, bus stops are stocked with sprinklers that create a cool cloud of droplets around them. But zealous Germans, taking care of creating a comfortable environment, do not forget about saving resources: they collect rainwater so as not to spend drinking water on irrigation. Underground rainfall tanks are going to be built in Stuttgart, and in Münster, conscientious citizens who water plants with rainwater and plant green roofs receive discounts on tap water – up to 80%.

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