Excessive heat in the indoor environment can be effectively mitigated by use of fans or modern air-conditioning systems. How can such conditions be altered outdoors? A radiant cooling approach has been devised by University of California Los Angeles (UCLA) researchers to provide relief in outdoor spaces, particularly in urban areas.

The approach described in Nature Sustainability relies on water-cooled aluminum panels and see-through, infrared-reflective thin polymer film to deliver both efficient cooling and visibility. The lightweight, scalable structure is designed to make outdoor environments feel up to 10° F cooler without obstructing visibility or open space.

Field trials evaluated the radiant cooling potential of a 10 ft by 10 ft structure enclosing three hydronic panels that circulated chilled water to keep the space actively cool. Semi-transparent, infrared-reflective film helped block radiative heat from surrounding surfaces, improving thermal comfort. The inward-facing side of the panels were painted black to absorb incidental heat, such as body heat from people within the structure.

The cooling structure was observed to have a mean radiant temperature of about 78° F, lower than the ambient air temperature of approximately 84° F and more than 10° F cooler than the mean radiant temperature of about 90° F that a person would have experienced due to heat radiating from surrounding surfaces. Most study participants reported feeling cooler and more comfortable than they would in shade alone.

According to the researchers, “This low-cost and scalable design is a practical step beyond shade to help people who have to be outdoors on hot days, especially during periods of extreme heat. This additional level of cooling can bring some relief in outdoor places where traditional air conditioning simply isn’t possible, such as metro stops, parks and plazas.”