This post is part of our definitions series on “eco-lingo” and technical terms.

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Image: U.S. EPA

“Green roofs”, or roofs that use vegetation to retain stormwater and reduce the ‘heat island effect’ of miles of sun-absorbing rooftops, are more well-known than a related roof-type, the “blue roof”.

Blue roofs use stormwater capture devices rather than vegetation to reduce runoff levels from rooftops. Blue roofs can contribute to sustainable building design and retro-fits in a number of ways. Some blue roofs are designed to temporarily harvest and house stormwater others may divert and infiltrate  or slow-release stormwater. Since areas with large amounts of impervious paved surfaces may be subject to flooding, blue roofs can reduce the risk and associated damage and expense of localized flooding.

Blue roofs can also be employed strategically to avoid over-burdening combined sewage systems that are in danger of overflow and discharge into water bodies during storms.

New York City unveiled a new Green Infrastructure Plan in September that will employ blue roofs among its strategies to reduce sewage overage a target 40% by the year 2030.

Read an article on NYC blue roofs, here. A further definition of blue roofs can be found, here.

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What exactly does “sustainability” mean? How about “green”, “eco” or “environmentally friendly”? The truth is that these terms are just vague enough to mean many different things to many different people. With the staggering array of “green” products, ‘lifestyles’ and concepts being promoted by marketers and environmentalists alike (as well as the necessary coining of new terms to match new ideas) our definition series aims to make sense of the rising tide of “eco-lingo” and technical terms.