The green choice of France: plants or solar panels for all new buildings’ rooftops

A new law recently passed in France mandates that all new buildings that are built in commercial zones must be partially covered in either plants or solar panels.

Green roofs are already very popular in Germany and Australia, as well as Canada’s city of Toronto, where a similar law has been in force since 2009. Planting the rooftops of urbanized areas brings many benefits to public, private, economic and social sectors, as well as to the local and global environments.

Here are the top 5 reasons to chose a green roof.

1. Green roofs reduce stormwater runoff. Green roofs increase water retention and can reduce water run-off by 50–90 %. Stormwater that leaves the roof is therefore delayed and reduced in volumes. Outlets, pipes and drains can thus be reduced in capacity, thereby saving construction costs. Finally, retention and delay of runoff eases stress on stormwater infrastructure and sewers.

2. Green roofs are energy efficient. In summer, the green roof protects the building from direct solar heat, while in winter it minimizes heat loss thanks to its added insulation. Energy conservation translates into fewer greenhouse gas emissions. Green roofs also improve air quality, as plants leave trap dust particles from the air, and evapotranspiration cools ambient temperatures.

3. Green roofs can serve as habitat. Low maintenance green roofs can be designed to serve as refuge for species such as ground-nesting birds. Vegetated rooftop habitats can also serve as stepping stones, to create corridors connecting other patches (roofscape or at grade) across an urban sea to natural habitats beyond the city.

4. Green roofs last longer. Green roofs cover the waterproofing membrane, protecting it from UV rays and extreme daily temperature fluctuations. This protection extends the lifespan of the waterproofing twice as long as conventional roofing, meaning that membranes under green roofs last twice as long as those on traditional roofs.

5. Green roofs provide ‘extra’ space. Green roofs make the most of unused space within the increasing density of our cities. Rooftops can be developed into social and recreational spaces and used for urban agriculture.

Everything considered, France is definitely on the right track.