Dry and sunny: How to cool overheated cities?

During the summer, surface temperatures in cities can reach up to 70° C, absorbing heat and feeding it back into the environment for hours, never truly cooling down

As another summer rolls around in the EU, many people who live in cities far away from the cool breeze of the sea or ocean are bracing for yet another season of record-breaking temperatures. As thermometers climb and rain becomes scarcer climate change is on the mind of many.  

In fact, according to the European Drought Observatory, in Southern France, a large portion of East Germany and Western Poland, as well as the Alps region are currently experiencing drought-like conditions.

This is why the Czech Environmental Partnership Foundation (Nadace Partnerství) published a set of measures that cities can implement to cool the urban environment. Their recommendations include ways to retain water and increase green spaces.

According to Martin Ander, a spokesperson for the foundation, we are not helpless in the face of extreme heat. Actually, cities can do quite a lot to disrupt heat islands and regulate temperatures.

Most importantly, the Partnership Foundation focuses on raising awareness about the importance of cooling certain surfaces like concrete and asphalt, especially on building facades and roads, as those are usually left to bake in the sun.

Surfaces can reach temperatures of up to 70° C on hot days

The key point of their recommendations centres around creating a positive feedback loop between urban greenery and water. As large population centres, by design, have a lot of concrete and asphalt - surfaces that absorb heat and release it well into the night, finding a cool space in a city is nearly impossible. According to a statement by the foundation, surface temperatures in cities can reach up to 70° C.

Not only that but, they also say that smaller rural towns can experience even greater heat. This applies especially to towns surrounded by tree-less agricultural land.

Furthermore, they provided a heat chart, comparing the temperatures on a green tram track to the adjacent asphalt road. The chart shows that the green track’s temperature sits at around 27° C, while the road is at around 40° C.

Greenery is good

Vegetation is key in both rural and urban areas, particularly trees, as they retain rainwater for longer and they evaporate more of it on hotter days, cooling their surroundings. The foundation claims that an adult birch evaporates around 70 litres of water on an average day, however, that number can go up to 400 litres as temperatures rise.  

They also recommend replacing asphalt and concrete whenever possible with grass paving or gravel lawns. Additionally, implementing designs to retain rainwater like seepage belts, rain beds, manholes or collecting ponds would also help feed the tree population.

Martin Ander was quoted in a press release, saying: “We can build or modify our housing so that it does not overheat on hot days. We paint the facade and roof with a light colour that reflects more sunlight back into the surroundings. Let's plant greenery around the house, use climbing plants or even a green roof. It is also important to shade from the outside using outdoor blinds, shutters, pergolas or awnings, or ventilate in the early morning and evening.”