Can Painting City Streets Reduce the Urban Heat Island Effect?


The impervious surfaces in a city such as streets, parking lots, and buildings absorb solar radiation during the day.  This absorption of heat from the sun creates higher temperatures than adjacent vegetative areas.  This phenomenon is known as the Urban Heat Island Effect.  During the summer months, urban heat islands can create higher temperature conditions that are 1-3°C (2-5°F) warmer than in nearby rural areas.  Higher temperatures result in higher energy costs from increased air conditioner use and high air pollution [1].

Differences in ambient air temperatures between urban, suburban, and rural areas. Image: Berkeley Lab Heat Island Group.

Differences in ambient air temperatures between urban, suburban, and rural areas. Image: Berkeley Lab Heat Island Group.

Cool Pavement Pilot Project in Los Angeles

The City of Los Angeles is experimenting with lowering the urban heat island effect by painting its streets a lighter color with a pilot project known as “Cool Pavement” [2].  A light gray reflective paint called CoolSeal will be applied to the majority of streets in Los Angeles in an effort to lower road temperatures across the city by up to ten degrees Fahrenheit.  The light gray paint boosts solar reflectively and reduces the overall temperature of road surfaces.  The CoolSeal coating costs $40,000 per mile and last seven years.  Painting the streets is part of a multi-pronged that includes cool roofs and more vegetation to reduce the overall summer temperature of Los Angeles by three degrees Fahrenheit [3].


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Diagram illustrating how Cool Pavement coating will increase solar reflectivity

Diagram illustrating how Cool Pavement coating will increase solar reflectivity. Source:

References

[1] Akbari H, Menon S, Rosenfeld A. 2009. Global cooling: increasing world-wide urban albedos to offset CO2Climatic Change, 94 (3-4), 275-286.

[2] Los Angeles Tests Whether Lighter Color Streets Will Lower The Temperature.  NPR.org, August 23, 2017

[3] L.A.’s mayor wants to lower the city’s temperature. These scientists are figuring out how to do it. Los Angeles Times, February 9, 2017

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