In most urban areas around the globe, summertime temperatures can turn cities into what might seem like a hellscape at times. In some cities shops and businesses even close during the hottest parts of the day. Los Angeles Mayor Eric Garcetti has started an initiative to combat the extreme summer temperatures - by painting streets white.
Coated tarmac surfaces are between 10°F and 15°F cooler
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Regular black asphalt absorbs between 80% and 95% of the sun's rays, heating street surfaces up to 70°C or 150°F. This can result in raising the ambient temperature by as much as 5°C to 10°C or around 20°F. This results in stifling and unhealthy conditions for residents. With the white coating, these rays are reflected away from the road surface and the surface itself is a lot cooler. City officials in Los Angeles experimented with the idea by painting 15 streets with the white seal-coat, supplied by a company called GuardTop. They found that the surface of the roads were between 10°F and 15°C cooler than uncoated surfaces, resulting in cooler ambient temperatures for the surrounding houses.
Officials calculate that if 35% of LA's streets were painted white, it would translate into a total city-wide drop of 1°. This might sound like a negligible difference, but it would translate into an estimated $100 million per year saving on energy costs. This would mainly be saved on air-conditioning, refrigeration and water costs. Not to mention that there might be some respite for residents of the city, who experience 1000's of cases of heat stroke each year. Heatstroke is a condition caused by your body overheating, usually as a result of prolonged exposure to or physical exertion in high temperatures. This most serious form of heat injury, heatstroke, can occur if your body temperature rises to 104°F (40°C) or higher.
The coating, a water-based asphalt emulsion, is sprayed onto the tarmac surface with trucks, and is then spread evenly by workers with squeegees. The coating then takes about 24 hours to dry. A second coat is then applied, and these coats can last up to seven years. Although the energy savings are enormous, the coating doesn't come cheap at $40,000.00 per mile.
Workers applying the coating with squeegees
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If this idea can really take shape and transform Los Angeles and provide the energy savings as estimated, it can be used in all cities around the world, and with a global climate that is heating up, this could combat global warming if all the factors are considered, especially if cities are using much less energy to keep cool.
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Sources:
http://www.demilked.com
http://www.mnn.com
http://www.businessinsider.com