Green roofs and walls, a brilliant idea

Some ideas are very promising to help us in mitigating climate change and among them are green roofs and walls.

Planting grass or trees like in Manhattan (cf. picture) on top of buildings have many advantages as it decreases the air pollution, the local temperature of cities and greenhouse gases emissions and so on.

In this article I will review the various specificities of green roofs and walls and what they can bring to large and medium sized cities.

There are numerous advantages to such roofs as they :

  • Improve the insulation of the building in an important way, indeed to : “Green roofs have a positive effect in terms of thermal insulation through their ability to cool buildings and insulate them during the winter.”
  • Absorb the carbon dioxide present in the air and generate oxygen thanks to photosynthesis, . Various air pollutants are also absorbed. To : “Green roofs reduce the heat island effect, which is the main cause of ozone production ; Plant roofs remove heavy metals, airborne particles and volatile organic compounds.”
  • Decrease the temperature within cities.“Roof areas are a significant part of urban hard surfaces. Plants on green surfaces absorb heat and then use it through evapotranspiration. Green roofs therefore would play an important role in reducing urban temperatures, and subsequent improvements in air pollution/smog, as associated with the albedo effect.”
  • Absorb the excess water as “Green roofs store rainwater in the plants and growing mediums and evaporate water into the atmosphere. The amount of water that is stored on a green roof and evaporated back is dependent on the growing medium, its depth and the type of plants used. In summer green roofs can retain 70-80% of rainfall and in winter they retain between 25-40%.”

On top of all these advantages, green roofs can be combined with solar thermal or photovoltaic panels so roofs can still be used to generate hot water or electricity.

Green walls also exists and their advantages are similar to those of green roofs.

In France such a concept is very seldom seen. However, the train station of Perrache in Lyon installed last month 200 square meters of green walls to decrease the air pollution from its parking lot.

To infer this article, I would like to state that albeit the sources I found gave many advantages on such roofs, I found no reliable data on the costs. The article on Wikipedia mentions a price of 15 to 35 USD per square foot but no source is given.

Further reading :

  • For more data on this subject, you can consult the website which is an “Independent UK Resource For Green Roof Information”.
  • For data regarding green roofs in the United States and Canada, one can have a look at According to this website, there are currently 639 projects due to create up to 444,623,650 ft² of green roofs ( 445 km²).


Edouard is a sustainability and energy professional committed to bringing our societies to a carbon neutral future. He has been writing on related topics on this very blog since 2007.

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7 Responses

  1. nao sei falr sua lingua e por isso nao te entendo e nao sei como transformar o simples telhado de minha casa em um telhado verde e tambem nem tenho dinheiro

  2. Hi there! Tks for commenting on! And as I saw, your portuguese is better than my english… :0

    congratulations for your work here, i’m recommending your blog for several of friends who want to read more about eco-news!

    jorge cordeiro

  3. Blog do Planeta, a friend of mine, gave a post about this post of yours. Check it out!

  4. Edouard says:

    Hi Jorge and many thanks for your comments and trackback !

    I sent you an e-mail and hope you will receive it.

    Have a nice day !

  5. Cameron Honaker says:

    Superb site you have here but I was curious if you knew of any forums that cover the same topics discussed here? I’d really like to be a part of community where I can get opinions from other experienced individuals that share the same interest. If you have any suggestions, please let me know. Thank you!

  1. Friday, June 12, 2009

    […] idea reminded me of my post on green roofs as well as the series of pictures showing what would Tokyo look like if it […]

  2. Monday, April 12, 2010

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