Stormwater

Stormwater Systems Benefit From Green Roofs

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Credit: American Hydrotech
With their myriad benefits, green roofs are becoming increasingly incorporated into new and existing projects. The International Green Roofs and Walls Project Database lists 1,599 projects totaling 33,334,677 square feet, and the number is growing.

Green roofs—also known as vegetated or garden roofs—are key green infrastructure elements and are being increasingly recognized for their “valuable ability to absorb, reduce, and delay stormwater from reaching sewers or other grey infrastructure systems,” says Richard Hayden, garden roof product manager with Chicago-based American Hydrotech.

With their myriad benefits, green roofs are becoming increasingly incorporated into new and existing projects. The International Green Roofs and Walls Project Database lists 1,599 projects totaling 33,334,677 square feet, and the number is growing. Green roofs—also known as vegetated or garden roofs—are key green infrastructure elements and are being increasingly recognized for their “valuable ability to absorb, reduce, and delay stormwater from reaching sewers or other grey infrastructure systems,” says Richard Hayden, garden roof product manager with Chicago-based American Hydrotech. [text_ad] Green roofs work by storing rainwater in several areas of a layered assembly: in open pore spaces of the growing media and within the drainage and water retention system that underlies the growing media and plantings. The rainwater is retained until the assembly is completely saturated, and excess water is slowly released from the roof into the site’s stormwater system. Stormwater runoff volume also is reduced because of evapotranspiration, which cools the surrounding air. Green roofs filter particulate matter and chemicals through the plants, growing media, system filter, and drainage layers, mimicking natural hydrology systems such as wetlands and similar structures. In summer, most green roofs stay cooler than conventional rooftops and help buildings stay cooler with less heat flowing through the roof. Lower green roof temperatures result in less heat transfer to the air above the roof, keeping urban air temperatures lower as well. Green roofs are an option for stormwater management that not only reduces the volume of stormwater, but improves the water quality coming off of rooftops, notes Dr. Marty Wanielista, director of the Stormwater Management Academy at the University of Central Florida (UCF). “As another major benefit, green roofs put more oxygen into the atmosphere and reduce temperature around the building site,” he says. The Stormwater Management Academy serves as a research source for education and training programs in nationwide partnership with governments, non-governmental organizations, and industry. Green roof technology is one of the research areas at the Stormwater Management Academy, which also studies low impact development (LID) technologies, water-quality management and pollution control technologies to reduce receiving water impacts, erosion and sediment control with smart sensors and materials and system analysis, climate change impacts and urbanization efforts on flood and drought, and stormwater treatment and reuse. What started off as an effort to add green space on buildings for purely aesthetic purposes has morphed in a very important BMP option for handling rainwater at the point where it lands on the roof, Hayden points out. [text_ad use_post='27751'] American Hydrotech manufactures and supplies waterproofing and roofing components for projects worldwide. Its flagship product is the original hot, fluid-applied rubberized asphalt, Monolithic Membrane 6125. Originally developed in the 1960s as a waterproofing element for bridge structures in Canada, MM6125 is now used for creating green roofs. Its seamless application makes it impervious to the effects of the wet conditions that are typical of green roofs, says Hayden. In 1996, Hydrotech introduced the Garden Roof Assembly and has since supplied waterproofing, drainage materials, lightweight growing media, and plants for more than 2,000 projects in the US and Canada. “There are many municipalities like New York; Chicago; Philadelphia; Washington DC; and Portland, Oregon, where green roofs are being encouraged through incentives of various types,” says Hayden. “These cities are part of a significant and growing group seeking out innovative ways to minimize or slow down stormwater from reaching already overtaxed sewers.” SW_bug_web

Green roofs work by storing rainwater in several areas of a layered assembly: in open pore spaces of the growing media and within the drainage and water retention system that underlies the growing media and plantings.

The rainwater is retained until the assembly is completely saturated, and excess water is slowly released from the roof into the site’s stormwater system. Stormwater runoff volume also is reduced because of evapotranspiration, which cools the surrounding air.

Green roofs filter particulate matter and chemicals through the plants, growing media, system filter, and drainage layers, mimicking natural hydrology systems such as wetlands and similar structures.

In summer, most green roofs stay cooler than conventional rooftops and help buildings stay cooler with less heat flowing through the roof. Lower green roof temperatures result in less heat transfer to the air above the roof, keeping urban air temperatures lower as well.

Green roofs are an option for stormwater management that not only reduces the volume of stormwater, but improves the water quality coming off of rooftops, notes Dr. Marty Wanielista, director of the Stormwater Management Academy at the University of Central Florida (UCF). “As another major benefit, green roofs put more oxygen into the atmosphere and reduce temperature around the building site,” he says.

The Stormwater Management Academy serves as a research source for education and training programs in nationwide partnership with governments, non-governmental organizations, and industry. Green roof technology is one of the research areas at the Stormwater Management Academy, which also studies low impact development (LID) technologies, water-quality management and pollution control technologies to reduce receiving water impacts, erosion and sediment control with smart sensors and materials and system analysis, climate change impacts and urbanization efforts on flood and drought, and stormwater treatment and reuse.

What started off as an effort to add green space on buildings for purely aesthetic purposes has morphed in a very important BMP option for handling rainwater at the point where it lands on the roof, Hayden points out.

Join us in Atlanta August 18–22, 2019  for StormCon, a five-day special event to learn from experts in various water-related arenas.  Share ideas with peers in your field and across industries—exploring new stormwater management practices and technologies.  Click here for details

American Hydrotech manufactures and supplies waterproofing and roofing components for projects worldwide. Its flagship product is the original hot, fluid-applied rubberized asphalt, Monolithic Membrane 6125. Originally developed in the 1960s as a waterproofing element for bridge structures in Canada, MM6125 is now used for creating green roofs.

Its seamless application makes it impervious to the effects of the wet conditions that are typical of green roofs, says Hayden. In 1996, Hydrotech introduced the Garden Roof Assembly and has since supplied waterproofing, drainage materials, lightweight growing media, and plants for more than 2,000 projects in the US and Canada.

“There are many municipalities like New York; Chicago; Philadelphia; Washington DC; and Portland, Oregon, where green roofs are being encouraged through incentives of various types,” says Hayden. “These cities are part of a significant and growing group seeking out innovative ways to minimize or slow down stormwater from reaching already overtaxed sewers.” SW_bug_web

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Comments

  1. Thank you for referencing Greenroofs.com’s International Greenroof & Greenwall Projects Database! As the publisher and founder of Greenroofs.com I would just like to point out that the Projects Database is a living research database, by no means any where close to representing the current actual numbers of roofs and walls greened throughout the planet. But that’s our goal and we rely on all stakeholders to contribute. So we invite everyone to share your work with us and the world! For more info, please visit http://www.greenroofs.com/projects/.

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