To Combat Extreme Heat, Cover Your Roof In Hungry, Sweaty Plants

Sourced from Popular Science

Like hot dogs on Memorial Day or fireworks on the Fourth of July, melting roads are now an essential marker of summertime. In 2013, police closed parts of the M25 highway, which encircles the city of London, England, after asphalt started to melt, according to a BBC report at the time. In 2016, a viral video showed people in the Indian state of Gujarat losing their sandals to a ravenous roadway. And in 2018, the same thing happened in Australia (where the southern hemisphere summer begins in December), with local outlets reporting traffic came to a crawl as the pavement started to bubble.

To cope with goopy roadways, a cyclical spate of summertime deaths, and other dangerous side effects of extreme heat, cities are looking to a different kind of black top: your roof.

Steven Peck is the founder of Green Roofs for Healthy Cities, a Toronto-based organization that seeks to promote, showcase, and advance the emerging field of living architecture in North America. At its broadest, living architecture blurs the lines between organic and inorganic—plants and plywood, quails and concrete. Peck says one of the most effective tools in the living architect’s kit is “vegetative technology,” which includes things like green roofs and vertical gardens.

Green roofs replace or obscure asphalt shingles, black cladding, or other materials with plants. They’re aesthetically advantageous, of course: green roofs are near-universally considered attractive. When accessible to office workers, they’re a recreational hit. But these systems also have some serious environmental benefits. Plants, for example, slow rainwater’s descent to street level, reducing the chance of small-scale flooding, while filtering notoriously dirty stormwater.

They're also useful in a heatwave. Existing roofs are typically black and made of emissive materials that generate heat easily. As a result, the sun’s rays are readily absorbed and resulting heat is channeled into the building. But green roofs are covered in hungry plants, which greedily absorb the sunlight themselves. By replacing a traditional roof and replacing it with a living one, building residents below are spared the brunt of extreme solar heat.

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