Excessive heat retention in cities results in the urban heat island effect marked by elevated ambient temperatures, adverse health effects and increased energy consumption for cooling. Avenues to mitigate these impacts include the development of cool paint coatings, which contain additives that reflect the sun’s heat to reduce surface heat absorption and emission. A field study was conducted in the tropical environment of Singapore by Nanyang Technological University researchers to gauge the heat reduction efficacy of such paint coatings.

The real-world assessment focused on four rectangular buildings that formed two parallel ‘street canyons in an industrial estate. Cool paints were applied to the roofs, walls and road pavement in one canyon while the second served as an unpainted control. The extent of heat reduction afforded by the cool coatings over a two-month period was documented by environmental sensors that measured air movement, surface and air temperature, humidity and radiation, to see how well the cool paint coatings worked in reducing city heat.

The cool paint-treated canyon experienced up to a 30% reduction in heat released from the built-up surfaces during a 24-hour cycle, resulting in an air temperature lower than the conventional canyon by up to 2° C during the hottest time of the day. Pedestrians in the cool canyon can feel up to 1.5° C cooler.

The lower air temperature was attributed to the reduction in heat absorbed by and stored in the building walls, roofs and roads, and which would subsequently have been released to either heat up the surrounding air or the building’s interior.

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The study published in Sustainable Cities and Society confirms that compared to conventional roofs, those with the cool paint coating reflected 50% more sunlight and absorbed up to 40% less heat.

To contact the author of this article, email shimmelstein@globalspec.com