Vegetated, or “green,” roofs provide numerous social and environmental benefits to urban areas. Compared with conventional roofs, green roofs promote biodiversity, reduce building energy use, decrease noise, and improve the productivity of solar photovoltaic installations. They can also mitigate the urban heat island effect and reduce stormwater runoff, thereby diminishing flooding and pollution of local waterways. As the effects of climate change worsen, and extreme heat and rainfall events become more common, these attributes will become all the more valuable. And with roofs typically occupying between 20 and 25 percent of urban surface area, transforming this space could substantially impact the local environment.
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