Green roofs: green lungs in the city

Green roofs: green lungs in the city

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Green roofs are a perfect solution for combining aesthetics and ecology, in cities as well as in rural areas. A concept booming in France but still little known to the general public.

What's the point ?

A roof covered with vegetation offers a number of environmental benefits. Thanks to its water retention capacity, it limits the risk of flooding in the city. In summer, it refreshes the building it covers. It also improves the thermal and acoustic performance of the building, protecting it from cold, heat and noise. Another significant interest: plants filter particles of pollution, cleaning the air in the city.

How it works ?

A green roof is made up of several layers. On the roof (whether concrete, wood, steel or other material), first install a thermal insulation component and then a waterproofing coating that resists root penetration. Above, we apply a drainage layer, a filter layer, a substrate layer and finally the plant layer. This is done by sowing, planting or pre-cultivated elements (in rolls or plates). The plants are most often sedums (Acre, Album, Floriferum, Reflexum, Sexangulare, Spurum), from the succulent family. These are rockeries, which have the particularity of storing water in their leaves.

In France also ?

If Germany and Switzerland have been interested in it for a number of years, this has only been the case of France for 5 years. Today, they are trying to catch up. As proof, the number of m² of green roofs jumped 50% between 2007 and 2008. Since 2002, their number has thus increased from 65,000 to 300,000 m², with 90% of construction sites in the new. A phenomenon that illustrates an environmental awareness.

Which systems?

In France, there are three different systems: - Intensive revegetation, otherwise called traditional garden roof terrace. We transpose on the roof the elements of a garden as we can find it on the ground: large thickness of topsoil, tall plants, trees. Maintenance is the same as it would be on the ground. This system can only be installed on a concrete support and with a slope of less than 5%. - Semi-intensive vegetation, which is an improved garden terrace due to the choice of growing materials (ground cover plants, perennials, shrubs, etc.). Maintenance is less important than for a traditional garden roof. - Extensive revegetation, the most commonly used on roofs. It is no longer a garden but a plant carpet. The culture materials are thin and rigorously chosen. As the weight is limited, this system allows planting light supports, in particular existing terraces, even on slopes (up to 20%). Maintenance is simple and limited to a maximum of three passages per year.

Who is it for?

Everyone, from the moment the roof is technically suitable and the city authorizes green roofs. It can be a private individual for his house but for the moment, there are mostly green roofs on apartment buildings. Some cities like Paris are very favorable to their establishment.

How much does it cost ?

It all depends on the nature of the roof (the more it is sloping and the more complex and expensive), the age of the building (it is more expensive on old than on new) and on the geographical location. compared to the supplier. The prices are on average between 50 and 120 € per m² including installation, excluding waterproofing and insulation membrane. Certain regions such as Hauts-de-Seine and the Ile-de-France region award grants under certain conditions. > Find out more: Adivet (Association for the development and innovation in extensive roof greening): Soprema:


  1. Carvell

    I still heard nothing about this

  2. Gadhra

    There's something about that, and it's a great idea. I am ready to support you.

  3. Telamon

    Congratulations, your thought is great

  4. Basilio


  5. Ahmar

    Author keep up the good work

  6. Akinogal

    To each according to his capabilities, from each according to his needs, or whatever it was written by Karl Marx

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