greenroof2A meaningful change to commercial building code has been confirmed in France: rooftops on new buildings must either be partially covered in plants or solar panels, under a law approved on Thursday.

Green roofs have an isolating effect, helping reduce the amount of energy needed to heat a building in winter and help cool it in the summer. Living roofs also retain rainwater, and aside from helping reduce problems with runoff, they also increase local biodiversity and give birds a place to nest in the urban jungle.

The law, approved by parliament on Thursday, was more limited in scope than initial calls by French environmental activists to make green roofs that cover the entire surface a mandatory part of all new buildings. No matter how you spin it, though, living roofs that fix carbon and increase biodiversity are a big step up from simply waterproof roofs.

The government convinced activists to limit the scope of the law to commercial buildings, despite initial calls to make it apply to buildings universally. The law was also made less costly for businesses by requiring only part of the roof to be covered with plants, and giving them the choice of installing solar panels to generate electricity instead.

Green roofs are popular in Germany, Switzerland, Australia, and Canada, with the city of Toronto adoptig a by-law in 2009 mandating them in industrial and residential buildings. Many are, wisely, calling for a re-greening of commercial and residential landscapes.