#Colorful wave full#

Using white or light-colored cool paints can bounce the sunlight and its heat away from the building, so indoor temperatures stay lower (or need less energy for air conditioning). Less attention has been given to the idea of cool walls, but Levinson’s group has recently shown that they can rival cool roofs as an effective way to reduce urban heat islands, while lowering indoor air temperatures or the need for AC.Īlthough walls get less direct sunlight than roofs, they are also less well insulated, so when sunlight hits them, heat is easily transmitted inside. The shift to cool wallsĬool roof technology has been around for more than two decades - and in some parts of California, it is now required for new construction and roof replacements. Credit: /iStockĪnd there are already many products available on the market, in a range of matte colors and materials, with costs that are comparable to conventional materials. Although they’re not as cool as white, these “cool colored” roofing materials can reflect up to 60 percent of sunlight, making them significantly cooler than typical dark asphalt shingles.Ī house with a cool roof.

#Colorful wave full#

Products colored with special pigments can reflect that invisible light while still offering a full color palette, bringing significant levels of cooling. About half of sunlight arrives as invisible “near infrared” radiation.

Being less reliant on AC comes with other benefits: It lowers cooling costs, takes stress off the electrical grid, and reduces the emissions that form both smog and greenhouse gases.Ĭool materials don’t need to be blindingly white or cast an obnoxious glare to work. That keeps buildings cooler inside, reducing the need for air conditioning by up to 15 percent or making spaces without air conditioning more comfortable. Minimizing those heat islands largely comes down to using building and paving materials that reflect the sun’s heat rather than absorbing it, Levinson said. Tree shade and evaporation from plants also help cool cities, he added.Ī white roof can reflect 80 percent or more of the sunlight.

Even at night, the built environment continues to release stored heat, creating nighttime urban heat islands that can be even more severe than those during the day. Concrete buildings, asphalt parking lots, paved roads, and dark rooftops all absorb the sun’s heat and then radiate it back out, warming the air. Some of that heat comes from the sheer density of people and their daily activities.īut much of it comes from the built environment itself. cities can average 5–9 degrees Fahrenheit (3–5 degrees Celsius) hotter than the surrounding countryside. Why cities are so hotįor more than 200 years, people have understood that cities tend to be hotter than the rural areas surrounding them, an effect described as urban heat islands. “There is urgency to this work because it’s only getting hotter,” said Berkeley Lab scientist Ronnen Levinson, who leads the Heat Island Group, a research unit focused on developing and testing solutions to urban heat. There is also a growing body of research aimed at developing new materials and techniques to help cities cool. Many of those interventions focus on delivering relief to the low-income neighborhoods that are most at risk during heat waves. Researchers and scientists from across the University of California and Lawrence Berkeley National Lab are working on a range of solutions to help cities and people cope.