MNN - Mother Nature Network

Anyone who's taken a midsummer stroll through Manhattan might appreciate this. Light-colored, heat-reflecting asphalt and paint makes a parking lot cooler by 40 degrees Fahrenheit (22 degrees Celsius) on a hot day.

 

The idea of painting city sidewalks, walls and roofs white isn't new, but we happened to run into a nice demonstration of it recently. The Lawrence Berkeley National Laboratory in Northern California has painted one of its parking lots with several commercially available heat-reflecting coatings, to show what a difference they can make and to test how they'll fare over time: 

 

 

In general, heat-reflecting surfaces keep cities more comfortable, reduce residents' electricity use for air conditioning and reduce the amount of heat that cities reflect back into the atmosphere, contributing to global warming. They can even improve air quality. "Across an entire city, small changes in air temperature could be a huge benefit as it can slow the formation of smog," Haley Gilbert, a research assistant at the Berkeley Lab who studies heat in cities, said in a statement.

 

White-painted roofs usually get the most attention, but paler pavements could make a big difference, too, researchers say. Pavement accounts for 35 to 50 percent of the surfaces in city, according to the Berkeley Lab. Since city dwellers spend much more time on sidewalks than they do on roofs, paler pavement would be an improvement they could immediately appreciate.