Chicago's roofs are the greenest by far -- at least in America -- where more than 2.5 million square feet of the city's blank roof space has been converted into gardens. Though they have long been installed in Europe, rooftop gardens are relatively new to the states. And as Chicago's city council has just recently approved a pilot program to match developer funds for installing rooftop gardens, their numbers are sure to rise.
"The idea is simple: bring back some of the organic material displaced by buildings, streets, and parking lots. Advocates tout benefits that range from reducing the urban "heat island" effect - which makes cities several degrees warmer than surrounding areas and can translate into millions of dollars in energy costs - to lengthening the life span of a roof, providing community garden or recreation space, and contributing to a building's energy efficiency."
" 'Cities are just going to keep getting hotter," says Steven Peck, president of Green Roofs for Healthy Cities. "So you take away hot surfaces and turn them into air conditioners. Green roofs do that very, very well.' "