Frances’s new “green roof” law is cooling city streets, cutting heating and air conditioning costs, reducing water and air pollution, providing local, organic food and ecosystems for birds, bees and hundreds of other species
In an effort to make concrete jungles more eco-friendly, France recently passed a law requiring the rooftops of all new buildings in commercial zones to be fully or partially covered in plants or solar panels.
The concept, known as “green roofs,” is becoming so popular in some cities, like Paris, that even the owners of old buildings are voluntarily complying with the law, building giant rooftop farms, meadows and apiaries for bees and other pollinators.
1.The reason city streets can be so sweltering hot in the summer is because their aren’t many or any trees to cool down the air.
Because there is little or no vegetation to absorb the sunlight, it is converted into heat energy, creating an phenomenon known as the Urban Heat Island Effect.
The daily dew and evaporation cycles of green roofs and walls are able to mitigate this effect, according to GreenRoofs.org.
2. Rooftops are the greatest source of heat-loss in the winter and heat-gain in the summer.
Green roofs provide extra efficient insulation, keeping heated air from escaping upward and absorbing sunlight that would otherwise beat down on the dark rooftops.
An extensive green roof in Canada reduced the demand for air conditioning in the summer by over 75%.
3. Rooftop gardens can capture airborne pollutants and filter noxious gases.
That’s because plants, especially bigger plants act as air purifiers.
Also because they reduce the need for heating and AC, power plants release less CO2 and other polluting byproducts into the air.
4. In summer, green roofs can absorb between 70 and 90% of the rain that falls on them.
This reduces the amount of storm-water that runs off buildings into overburdened sewage systems.
Urban runoff is a huge problem in which all the rainwater that hits polluted city surfaces (rooftops, sidewalks, streets) rushes into city sewers and then drains straight into rivers and lakes.
Because so much of the surface area of cities is impermeable, urban flooding is also a problem.
Rooftop gardens, especially those with deep roots and soil, can reduce both of these problems by absorbing the water and filtering any runoff.
5. Because the people who install rooftop gardens tend to be ec0-minded folks, they tend to use organic agriculture, or better yet permaculture, providing fresh, local, organic food for local restaurants and citizens.