These roofs can clean the air

Roofing tiles protect homes from the environment, reflecting heat from the sun and keeping rainwater rolling away into gutters. Thanks to work done by students at the University of California at Riverside, however, roof shingles may soon be protecting the environment itself.

A team there coated off-the-shelf clay roofing tiles with titanium dioxide, a compound found in "everything from paint to food to cosmetics," according to the researchers. They then placed the coated tiles into a mini atmosphere chamber they built out of wood, Teflon, and PVC pipes. The chamber was filled with nitrogen oxide and beamed with ultraviolet light to mimic the sun. Nitrogen oxides are compounds in the air that are responsible for causing smog.

What they found was that the coating on the tiles removed between 88 percent and 97 percent of the nitrogen oxides. This led them to calculate that an average-size residential roof coated with their titanium dioxide mixture could break down the same amount of smog-producing nitrogen oxides per year put out by a car driven 11,000 miles. They further calculated that 21 tons of nitric oxide could be eliminated every day if tiles on 1 million roofs got the coating.

And the price for the simple yet powerful smog-busting coating? Just about $5 to cover an average-sized roof.

The students on the team that executed the research and developed the titanium dioxide coating are graduating in the fall, but are hopeful that new students will take over their work and test other factors.

"For example, they want to see what happens when they add their titanium dioxide to exterior paint," said a UC Riverside statement. "They are also considering looking at applying the coating to concrete, walls or dividers along freeways. Other questions include how long the coating will last when applied and what impact changing the color of coating, which is currently white, would have."