Blue Roofs: Smart Stormwater Systems

Building owners generally frown upon water pooling on a roof, but with careful detailing, roofs can be a good place to store excess rainwater. Storing water on roof makes sense in urban areas when there is little free space on the lot, or when putting it in the ground is expensive or inappropriate, such as on brownfield sites. These “blue roofs” are not a new concept and are often integrated into green roofs to provide additional water storage, but Hanging Gardens has improved the versatility of these systems by using smart drains and other technology to better manage stormwater runoff.

Blue roof basics

Blue roofs typically use waterproof membranes, barriers (such as dams, gravel, or specialized mats), low-flow drains, and other means to hold water on a roof, where it can then evaporate or slowly drain into the sewer or a stormwater system. Unlike green roofs, blue roofs do not use plants or growth media to filter rainwater, but in communities with combined sewer and stormwater runoff, they can help keep water treatment facilities from being overwhelmed and dumping raw sewage into the watershed.