France mandates solar or green roofs for all new commercial buildings

The French Parliament approved a new law that will require the rooftops of newly constructed commercial buildings to be partially covered with either plants or solar panels. The legislation – which applies only in France’s commercial zones – calls for 50 percent of new rooftop space to be outfitted with solar technology or natural vegetation.

The newly enacted law follows on the heels of a lengthy campaign by environmental activists to have new commercial rooftops across France covered entirely with grass. Lawmakers, however, opted for a less stringent law, citing economic concerns for businesses. The French Parliament agreed on a compromise that would give businesses the choice of installing solar panels in lieu of planting foliage. 

Environmentalists and supporters of the initiative believe green rooftops play an instrumental role in alleviating the effects brought on by climate change. The addition of grass and solar panels to commercial rooftops will not only help generate clean electricity but also help buildings deflect sunlight, thereby making them more energy efficient.

The extra insulation enables buildings to stay cooler during the summer months and warmer during the winter months. Green rooftops can also help in reducing urban heat island effects and retaining rainwater, thus reducing problems with runoff. Ecologists also point to green roofs as ideal an ideal setting for fostering biodiversity.

The benefits of green roofs were highlighted perhaps most notably in a 2009 study commissioned by scientists at Michigan State University.  The researchers measured carbon levels in plant and soil samples collected from 13 green rooftops in Michigan and Maryland over a two-year period. The study found that by replacing traditional roofing materials with green roofs in an urban area the size of Detroit – a city with a population of approximately 1 million people – an estimated 55,000 tons of carbon would be captured. This is roughly equivalent to the amount of carbon dioxide that is emitted by 10,000 mid-sized SUVs and trucks every year.

In addition to the environmental benefits, the new law will perhaps jump-start the spread of solar technology in France, which has historically lagged other European countries like Germany, Italy, and Spain in photovoltaic capacity. As of last summer, France had only five gigawatts of capacity, a small fraction of Germany’s 40 GW. France continues to rely heavily on nuclear energy, with as much as much as 80 percent of the country’s electricity coming from this source alone.

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