green roofs

    Reinventing the Traditional Vegetated Roof for Detention – an application of whole-system thinking

    “Green infrastructure focuses on cost-effective, living, upstream solutions. And there is no-where farther up stream than the roof! Green infrastructure is so powerful because it harnesses the simple solutions of nature to provide primary and secondary benefits,” states Charlie Miller, one of the key people behind friction-detention technology. “By virtue of their huge surface area and their large lateral extent, green roofs change the hydrologic response of the roof surfaces that they cover.”

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    HOW A VEGETATED GREEN ROOF CAN ACHIEVE MORE DETENTION: “A new technology involves replacing the traditional fast-draining drainage layer with a ‘friction’ or ‘detention’ layer to ensure that during large storms, runoff rates are lower than rainfall,” stated Sasha Aguilera (November 2019)

    “Imagine a traditional vegetated roof of customary design. The vegetated roof acts like a sponge. However, when the sponge is wet, the entire system is designed to drain rapidly,” wrote Sasha Aguilera. “Though it is possible to achieve detention via increased distance to drain and reduction of the slope, those two changes are often impractical or impermissible. However, the introduction of friction to a vegetated roof system is possible; thus causing a temporary accumulation of water within the vegetated roof.”

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