In the month of March 2015, France approved a law which requires all new buildings in commercial zones must either be covered partially by plants or solar panels. The reasoning behind this change in policy is that green roofs help reduce stormwater runoff as well as provide birds nesting grounds in urban settings.
Green roofs are popular in Germany, Switzerland and Australia. They are gaining popularity in North America, with Toronto mandating in 2009 the construction of green roofs on building with gross floor area greater than 2000 square meters. Cities like Chicago, New York City, Washington D.C. and Philadelphia are offering tax incentives to buildings with green roofs. In densely populated urban areas, green roofs can lower the heat island effect (a metropolitan area that is significantly warmer than its surrounding rural areas due to human activity).
Another main benefit of green roofs is adding to the lifespan of a roof. Typically, a green roof costs on average $15 a square foot (http://www.greenrooftechnology.com/green-roofs-explained). Such a high cost is offset by the roof life spanning between 30 and 50 years.
Hopefully, the trend which started in France will continue in North America. But in the meantime, check out the map provided by the city of Chicago with the location of green roofs in the city using the following link (https://data.cityofchicago.org/Environment-Sustainable-Development/Green...).