Back in February Philadelphia’s Mayor Nutter announced the “RetroFIT PHILLY Coolest Block” contest, in which Philadelphia row home owners or occupants enter to have their entire block upgraded for energy efficiency–for free. The winning block will start with an energy audit, the installation of a “cool roof,” insulation products with a free install, and a block party to celebrate the win.

A free block party? Now that is cool.

A big goal of the contest is to attract interest in the benefits of the “cool roof”, one with a white coating that can help make roofs 50-80 degrees cooler and save as much as 20% of a home’s cooling costs. Interesting or not, Philadelphia will be seeing a lot more of them in the coming years. On May 13 a city-wide legislation will be signed requiring all new no- and low-slope roofs to either have the white reflective roof or a green roof.

Maybe by law, then, Philadelphia will be the Greenest City in America.

Check back in on May 13 to see which Philly block wins the contest.