It’s serious crunch time in France for environmental policymaking as regulations tighten in deference to the 2020 goal of reducing carbon emissions by 25 percent. Paris is also scrambling for brownie points as it prepares to host the UN Conference on Climate Change this November.
Lawmakers in France recently decreed that all rooftops of new commercial buildings must be covered in either plants or solar panels. Other major cities have gone to similarly stringent lengths, with the city of Toronto, Canada, mandating green roofs on all new buildings in 2009—whether residential, industrial or commercial.
Expected foliage cover ranges from 20 to 60 percent depending on the size and type of building, with residential dwellings less than six stories high exempt from the mandate. Green roofs are an apt counterweight to the urban island phenomenon, in which urban zones are found to be several degrees hotter than surrounding rural areas because of their concrete density relative to moist, permeable land and vegetation.
On the other hand, green roofs create an “isolating effect” that cools the building, reducing energy needs for heating and cooling in winter and summer, and retain rainwater to reduce excess runoff and flood likelihood. A green roof also bodes $200,000 in savings over its lifetime, according to researchers at Michigan State University.
French environmental activists had initially lobbied for far less leniency, calling for every roof on every new building to be entirely covered by plants, without the option of installing solar panels instead. The Socialist government sought a middle-ground appeasement, convincing activists to limit the law to commercial buildings.
France still lags behind other European countries in terms of solar deployment, installing just 613 megawatts of solar photovoltaics in 2013, falling behind countries that had installed at least 1 gigawatt in previous years, according to a 2014 report by the European Photovoltaic Industry Association.