Why are Green Roofs and Blue Roofs vital to SUDS success?

The advantages of including of green roofs within SUDS strategies has been increasingly recognised as a key part of compliance with Governments Water strategy for England (DEFRA 2008).

Green Roofs

• occupy otherwise redundant roof space
• extend the waterproofing durability of the roof
• reduce energy consumption
• provideadditional amenity space
• help to reduce the peak rates of runoff

However, by combining a blue roof system where detention and maximum discharge are calculated using hard engineering principles with the additional retention capacity of a green roof, it is possible to realise not just the hydraulic performance requirements, but every aspect of SUDS design criteria.

Blue Roofs

• used in US cities for 50 years as a means of managing stormwater run-off in urban areas
• designed to alleviate flood risk by reducing and controlling the peak rate of discharge
• facilitates detention of stormwater up to a prescribed maximum hydraulic head, for subsequent discharge over an elongated period

Combining Green Roofs and Blue Roofs

Blue roofs can include open water surfaces but can also be used in buried applications, such as raised deck surfaces or green roofs. Indeed, by partnering a green roof with a blue roof system, the retention of stormwater in the green roofs layers, complements the detention of stormwater by the blue roof to provide valuable additional drainage capacity.

The Governments Water Strategy for England acknowledged that below-ground pipe systems cannot cope with extreme rainfall events, identifying the importance of SUDS and green roofs for water management and climate change mitigation. The combination of green and blue roof systems represents the ultimate sustainable roof drainage solution and the need for inclusion of these systems in our every-day architectural designs is already a reality.

Extract of an original BLOG article by Simon Poe, Product Director with Alumasc Roofing

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