On May 13, 2010 Mayor Nutter signed a new law, sponsored by Councilman Jim Kenney and passed unanimously by City Council, which requires all new commercial and residential construction to include reflective roofs, a feature that will reduce cooling costs and energy usage in the city. Unlike traditional black roofs, reflective cool roofs reflect the sun’s rays back into the atmosphere and release absorbed heat. This keeps buildings cooler and lessens the demand for air conditioning by 10 to 30 percent. On new construction, reflective roofs are comparable in price to traditional roofing materials but average energy savings of 20 percent.

http://cityofphiladelphia.wordpress.com/2010/05/14/mayor-nutter-announces-winner-of-retrofit-philly-%E2%80%9Ccoolest-block%E2%80%9D-contest-signs-cool-roof-legislation-into-law/