Asphalt - Los Angeles goes blank

L’asphalt dark is covered with a kind of titanium dioxide-based gelatin which, reflecting the sun’s rays, should contribute to lowering the ambient temperature by a few degrees (Fahrenheit): this is the technique experimented for the first time by the city of Los Angeles in an unusual approach to climate change, initiated with the sustainable city plan of 2015: a project that started with the whitewashing of some parking lots.

When too much (sun) is good. With 300 out of 365 days of clear skies a year and global warming starting to take effect, LA can become hell. By the middle of this century, the number of days of extreme heat could double. Many interventions have been developed to curb the “urban heat island” effect, which occurs when the ground is covered by a high concentration of asphalt, buildings and other surfaces that absorb heat. What most intrigued the Angelenos themselves is the layer, no more than a quarter of a millimeter thick, of a substance called CoolSeal, which was spread on some streets of the Californian metropolis in the second phase of the pilot project, launched in June 2017. Second the first tests, the reflective material manages to reduce the asphalt temperature by about 5 degrees Celsius, but only by 0.2 that of the air.

10% of “cool” surface by 2025. The goal of Mayor Eric Garcetti, elected in 2013 and reconfirmed in 2017, defined a “pragmatic progressive” very sensitive to environmental issues, is to reduce the temperature of the city by 1.6 ° C by 2050. For 2025 it should therefore be reflective 10% of the roads (which cover approximately 15% of the total area of ​​the Californian metropolis), a percentage that should increase to 30 in 2045. In the third phase of the program, which began in 2019, the 15 single patchy road sections switched to treating entire neighborhoods, choosing them according to the criterion of microclimate, lack of shade and disadvantaged economic conditions. According to the Green new deal that the mayor presented in the same year, in 2028 the “cool pavement” should cover 250 miles of urban routes.

The air conditioner roofs. Before moving on to “cool streets”, Los Angeles experimented with something similar, with good results, requiring new buildings or refurbished buildings to adopt roofs capable of eliminating the need for air conditioning systems.

All that is white is not gold. Will it be enough to whitewash Los Angeles to freshen it up? Waiting for results with a solid scientific basis, some studies have shown some perplexity. The material used to cover the asphalt could be more energy-intensive than traditional asphalt. In addition, negative effects were found on residents, pedestrians and motorists. The first two could even experience an increase in external temperature, while those behind the wheel can be dazzled. Finally, many believe that the action of trees, which, in addition to providing shade, capture carbon dioxide, is much more effective. It must be said that the Los Angeles plan provides for the simultaneous planting of the sides of the road together with the white asphalting. Being careful not to repeat the mistakes of the past. Everyone knows what happens when the roots of the tree instead of deep spread to the surface.

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