Beat the Heat: An Innovative Solution for Cooling Down in Summer

Summers are getting more dangerous, especially in cities where tall buildings, concrete, and asphalt make temperatures skyrocket. But there could be a simple and cost-effective solution to cool down urban heat: retroreflectors.

A recent study in the journal Nature Cities revealed that when retroreflective material was placed on buildings, it lowered the surface temperature by up to 36 degrees Fahrenheit and reduced air temperatures by almost 5 degrees.

Reducing the temperature of buildings is crucial for people walking on the street, according to Elie Bou-Zeid, a professor at Princeton University. He explains that the walls of buildings emit a lot of heat, which can be uncomfortable for pedestrians.

Bou-Zeid mentions that by cooling these surfaces by 36 degrees, people will feel much more comfortable. It is similar to the relief one feels when standing in the shade on a hot day.

Cities are much warmer than suburbs and rural areas due to their construction. Tall buildings, dark roofs, asphalt, and concrete absorb the sun's rays and release heat, known as the urban heat island effect.

Aerial view of typical buildings of Barcelona cityscape from helicopter.

Aerial view of typical buildings of Barcelona cityscape from helicopter.

Manel Subirats/iStockphoto/Getty Images/iStockphoto

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Urban designers are now using various strategies to combat urban heat, such as painting roads white, increasing tree planting, and constructing green roofs. However, researchers suggest that using retroreflective materials could be even more effective in cooling urban areas.

Retroreflectors work on a straightforward principle: they consist of mirrors in the shape of a cube corner that reflect light back in the original direction. A similar effect can also be achieved with a bowl-shaped mirror.

They are commonly found in road signs and bicycle reflectors to help drivers see them better at night. Reflective strips are also used in running clothes for increased visibility. Cats' eyes have natural retroreflectors, making them appear to glow when light is shone on them.

Street signs use retroreflective material so drivers can see them at night.

Street signs use retroreflective material so drivers can see them at night.

Joe Sohm/Visions of America/Universal Images Group/Getty Images

Retroreflective material could be created as sheets or coatings to be placed on city surfaces, offering a cost-effective solution to the rising temperatures caused by pollution. Small-scale trials have been conducted in the Netherlands and Italy, but large-scale implementation is challenging due to the retrofitting of existing buildings.

"The building industry can be slow to embrace new technology," explained Bou-Zeid to CNN. "Our aim with this paper was to highlight the cooling benefits of retroreflective material. The next important step is to further develop this existing technology for use in buildings."

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Some US cities have taken steps to tackle extreme heat. Los Angeles streets were painted with a grayish-white coating to reflect sunlight and keep air temperatures cooler. This is similar to how wearing a light shirt can keep you cooler than a dark one in the hot summer sun. However, researchers suggest that retroreflective material could be more effective as it reflects sunlight back toward the sun and not to other objects on the ground, according to Bou-Zeid.

One downside to using retroreflective material is that it could make winters feel even colder by reflecting sunlight during a time when it is beneficial. This may lead to new public health concerns. Bou-Zeid mentioned that it might be possible to design reflective materials that can be turned off when needed.

During the summer, the surfaces become white and reflect a lot of heat back to the sky. In contrast, during the winter, they turn black and absorb more of the sun's energy.

Cars travel through high floodwaters in Boston during high tide. New England residents were greeted with a coastal flood warning for the entire coast of Rhode Island and Massachusetts on up to Maine.

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(Photo credit: Erin Clark/The Boston Globe/Getty Images)

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To help combat the urban impact of the climate crisis, cities must implement various measures to adapt to and mitigate these changes, according to Xinjie Huang, the lead author of the study and a doctoral researcher at Princeton.

Huang emphasized that relying solely on retroreflective surfaces or any other single heat adaptation strategy is not a one-size-fits-all solution for different urban environments worldwide. Instead, a combination of cooling technologies tailored to specific localized conditions is necessary to address the increasing urban heat stress on a global scale.

Editor's P/S:

The increasing temperatures in urban areas, particularly in the summer, pose a significant threat to human health and well-being. However, the study discussed in this article offers a promising solution in the form of retroreflective materials. By reflecting sunlight back towards the sun instead of absorbing it, these materials can significantly lower surface and air temperatures, making cities more comfortable for pedestrians and reducing the urban heat island effect.

While the concept of retroreflective materials is not entirely new, their potential for use in urban cooling is still relatively unexplored. The study's findings suggest that these materials could be a cost-effective and scalable solution to help mitigate the impacts of rising temperatures in cities. Further research and development are needed to optimize the materials' performance and address potential challenges, such as their impact on winter temperatures. Nevertheless, the promise of retroreflective materials as a tool for urban cooling is undeniable and warrants further investigation and implementation. combating urban heat while addressing any potential unintended consequences.