New Finding for Urban Heat Islands

The urban heat island theory suggests that urban environments (human modified land surfaces) are hotter than nearby rural areas. Often times building materials used in urban areas retain heat, however urban areas also create waste heat, a secondary contributor to UHI that generates energy use from cars, factories, and more.

According to the Asphalt Pavement Alliance (APA) new research suggests that concrete pavements contribute to Urban Heat Islands (UHI), instead of reducing heat, as previously thought.

The urban heat theory suggests that urban environments are warmer than nearby rural areas, due to less vegetation, buildings constructed of materials that retain heat, and waste heat, caused by energy usage.

At one time light colored pavements were thought to reduce heat in urban areas (although not field-proven); however, new research by several universities indicates that dark-colored pavements do more to mitigate the UHI effect than light-colored pavements.

The National Center of Excellence for Smart Innovations at Arizona State University (ASU) is studying the impact of pavement characteristics on air temperature. The theory suggests that if pavement color has no impact on air temperature at, for example, 5 feet above the pavement, then pavement color has no impact on UHI.

Professor, Kamil Kaloush provided a summary of the study's initial findings and stated, "Air temperatures at 3 and 5 feet above the concrete and asphalt pavement surfaces are similar (< 1˚F difference). As such, factors like wind speed, rain, and humidity may have a more significant role in air temperatures above pavements than pavement surface material type."

ASU's findings are paralleled by a similar study from the University of California, Davis, which concluded that air temperatures 1 foot or more above light-colored and dark-colored pavements were not significantly different, however reflective pavements were shown to heat up adjacent buildings, actually increasing the UHI effect.

For more information about urban heat island theory, please visit epa.gov, or to learn more about the university studies being conducted please visit ucdavis.edu or asu.edu.

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