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Gray streets to combat climate change
For some time now, large cities have begun to adapt their different infrastructures and urban planning to try to combat climate change, where the concept of resilience is on the lips of many urban planners.
New techniques and findings are being implemented with really satisfactory results and in this case we want to talk about why we should paint the streets of our cities to combat climate change.
To understand this case study we have to move to the city of Los Angeles (USA). A city where the temperature in the last 100 years has risen 5ºC on average due to the heat island effect produced mainly by new highways, roads, large parking areas, new roofs… etc.
In Los Angeles, in the middle of summer, they can reach 10ºC (On average they range from 38ºC - 100 degrees Fahrenheit), being also that this summer it reached higher levels of heat since it has been recorded in the last 150 years.
The term "heat island»Describes those built-up areas that are warmer than nearby rural areas. According to the EPA (United States Environmental Protection Agency) The average annual air temperature of a city with 1 million people or more can be 1.8-5.4 ° Fahrenheit (1-3 ° C) warmer than its surroundings. At night, the difference can vary increasing up to 22 ° Fahrenheit (12 ° C).
Urban heat islands can affect communities by increasing peak energy demand during the summer, air conditioning costs, air pollution and greenhouse gas emissions, and heat-related illness and mortality. water quality. So we are not talking about a light effect!
One of the main causes is the black color of the asphalt that roams the streets and highways of our cities, which strongly absorbs the heat of the sun (Black asphalt absorbs between 85 and 95 of sunlight) and whose reflectance is estimated only 15 - 5%.
This summer, the city of Los Angeles began to test in different limited areas a new high-performance coating based on an asphalt that achieves lower surface temperatures before a lighter-colored surface - gray - and greater reflectance (It has a 40 - 33% solar reflectance). The comparative graph between cement - gray asphalt and black asphalt is:
The tests carried out in Los Angenes show more than satisfactory data, the temperature in some streets dropped to 6.6 ° C after a single layer of this new gray asphalt.
We are not just talking about reducing the average temperature of those hot cities, this also means less dependence on air conditioning in summer which will therefore mean less electricity consumption for homes and less greenhouse gases. Or that by having an asphalt with greater reflectance, night lighting can be reduced by obtaining the same vision and reducing the energy expenditure of administrations, not counting the health and comfort benefits associated with more moderate temperatures.
It is clear that there is still more research to be done as indicated in this article, but of course we are in the right direction, this is what many professionals in the sector agree. More information can be found in the report Reducing Urban Heat Islands - Cool Pavements.
Also of interest is the article 12 Ecological guidelines for sustainable cities in the face of smart urban development indicators.
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