Stormwater Management: Keeping Sewage Out of Our Rivers
Green roofs absorb and slow rainfall, reducing runoff and easing pressure on city sewers. They filter pollutants, improving water quality before it reaches waterways. By controlling peak flow, green roofs help prevent urban flooding and combined sewer overflows.
RoofBlue® RETAIN: Smart, Sustainable Stormwater Management
RoofBlue RETAIN™ is an innovative, cradle-to-cradle solution that captures and stores stormwater, then transfers it upward for plant growth and transpiration. Backed by University research, it outperforms mineral wool, retaining up to 1.35 gallons per square foot and increasing stormwater retention by up to 55% when paired with LiveRoof systems. Made from recycled, recyclable materials, it offers a lower cost per gallon retained and a significantly smaller carbon footprint than traditional options.
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Green Roof TypeDepth (inches)Water Retention (%)Water Retention (gal/ft²)
Lite 2" 40–60% 0.25–0.6 gal/ft²
Standard-Deep 4.25”–6" 50–75%. 0.6–1.2 gal/ft²
Maxx 8” 60–90%. 1.2–3+ gal/ft²
Add 1.35 gal/ft2 if using RoofBlue Retain
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Green roofs reduce total stormwater runoff by 40-80% through retention and evapotranspiration, while traditional detention systems primarily delay runoff without significantly reducing volume. Detention systems are better for managing large storm events and flood control, whereas green roofs provide continuous absorption, peak flow reduction, and water quality benefits, making them ideal for urban settings.
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Only use green roof engineered soil
Design with supplemental irrigation (overhead spray best) for the summer months
Schedule frequent, brief maintenance visits to monitor for proper drainage and tree seedlings
