France, after affixing vertical-axis wind turbines to power the Eiffel Tower's twinkling night lights, has taken an audacious approach to regulating new buildings’ energy consumption. French Parliament recently passed a law mandating that all new buildings in commercial zones must be partially covered in either plants or solar panels.

Green rooves have an isolating effect, which helps to reduce the amount of energy needed to heat a building during the winter or cool it in the summer. Plants on buildings are capable of retaining rainwater and reducing problems with runoff, and also offer birds a place to call home in the urban jungle. Vertical gardening, urban gardening, and rooftop gardens have long been applauded by environmentalists for their improvements to local air quality and their role in lowering localised temperature due to the heat island effect.

The law’s alternative of solar panels has the obvious benefit of offering a way to use the top of a building to generate renewable energy.

The current French government convinced activists to limit the scope of the law to commercial buildings. But still, in the final months ahead of the UN Climate Change Conference, which will be held in Paris, the French Parliament’s aggressive mandate on new commercial buildings is hugely positive.

France now has 10 times as many green rooves as Germany who pioneered the practice. The Canadian city of Toronto adopted a by-law in 2009 mandating them in industrial and residential buildings. Copenhagen, Basel, and the New York High Line have embraced the benefits of green rooves.