A blue roof is a roof design that is explicitly intended to store water, typically rainfall. Blue roofs that are used for temporary rooftop storage can be classified as "active" or "passive" depending on the types of control devices used to regulate drainage of water from the roof. A number of blue roof pilot projects have been implemented around the United States. Active blue roofs for storm water detention using forecast integration were first proposed in 2008. Active blue roofs are sometimes referred to as automated roof runoff management systems.
Recent work on blue roofs have involved pilot projects using stormwater collection. Blue roofs can provide a number of benefits depending on design. These benefits include temporary storage of rainfall to mitigate runoff impacts, storage for reuse such as irrigation or cooling water makeup, or recreational opportunities. Blue roofs can include open water surfaces, storage within or beneath a porous media or modular surface, or below a raised decking surface or cover.
A significant blue roof pilot project intended to evaluate the potential of the systems for mitigating combined sewer overflow impacts was conducted between 2010 and 2012 by the New York City Department of Environmental Protection. The NYCDEP blue-roof projects are the first to utilize a novel passive blue roof tray design which relies on the lateral transitivity of non-woven filter fabric for drawdown control in a full scale pilot. Monitoring of these systems has demonstrated their performance as an effective means for mitigation of peak flows and alteration of timing in combined sewer systems.
Blue roofs are often privately owned, and make efficient use of the otherwise very limited space available in the urban core of a highly populated city.
Some recreational blue roofs integrate rooftop waterplay areas that can also be used to irrigate a green roof, or to cool the roof of a building on hot days, in order to eliminate or at least reduce the HVAC load placed on mechanical refrigeration equipment.
Some blue roofs utilize stored water for beneficial on-site purposes cooling of solar panels and irrigation of a green roof. One example of a blue roof that provide ancillary services was the winning entry (First Place, 10,000 Euro prize) in the 2004 Coram Sustainable Design Award, by Steve Mann
- "Roofing and Plumbing Solutions". Retrieved October 17, 2014.
- "New Directions in Real-Time and Dynamic Control for Stormwater Management and Low Impact Development". Retrieved February 17, 2016.
- "NYC.gov Blue Roof". Retrieved August 20, 2012.
- "Roofing Magazine". Retrieved May 21, 2014.
- Winners, 2004 Coram International Sustainable Design Award, http://www.experientialdesignlab.com/projects/auxiliary-projects/blue-roof