Growing cities bring more air pollution. Cities such as Houston, Texas are using green roofs to combat air pollution and manage storm water runoff.
A recent NPR piece about growing and sprawling cities, states greater Houston's population at about 6 million people (podcast here ). With its hot and humid climate, as well as oil refineries, air pollution is a very serious issue. Additionally, as Houston grows, storm water runoff and its management also becomes a more significant issue, as much of the runoff ends up in the Gulf of Mexico.
The Houston Business Journal reported in 2007 people were thinking about and building green roofs. The green roof is 12% more efficient than a baseline building, and helps to reduce the urban heat island effect.
According to Wooten (Kirksey Associate Russell Wooten, project manager), green roofs address two green building issues that are of special concern in Houston:
The heat island effect. Green roofs reduce what is known as the heat island effect: Due to large areas of hot paved surfaces in urban areas, it's often up to 10 degrees hotter in the city than in the surrounding countryside.
Stormwater. The plant materials on green roofs absorb a large amount of stormwater.
...green roofs increase the roof's life span, filter pollutants and carbon dioxide out of the air and filter pollutants and heavy metals out of rainwater.
Another successful green roof project in Houston is the University of Houston Architecture School. Geoffrey Brune of the Architecture School states in a piece from ABC12.com:
" If all the buildings in Houston had green roofs then the temperature would be very different. … I think it would be significantly noticeable … by several degrees."
Additionally, the U/H green roof is on a building with a sloped roof, not typically seen with green roofs. The building is proving that green roofs are feasible on not just for larger structures with sloped roofs, but also for residential structures, which typically do have sloped roofs.
As Houston's population continues to grow, the application of green roofs to new buildings will help bring cleaner air to its new residents.