The blue roof is the lesser-known cousin of the green roof. Both represent sustainable roof drainage solutions but while the latter is frequently referred to in construction circles, the former has been somewhat overlooked.
Just like green roofing, blue roofing is not a new concept. It has been used in many cities in America for the last 50 years as a way to manage stormwater runoff in urban areas. But while there are trained blue roof installers and manufacturers in the US, up until now there has been no British or European standard written to cover this type of application. This is why a specially formed group of experts—the NFRC Joint Flat Roofing Technical Committee—have been tasked with producing technical guidance. Members include membrane and system manufacturers, insulation producers, standards and certification bodies, drainage consultants and representatives from flat roofing trade associations who will work together to create the regulation advice. This—like Green Roof Code of Practice (GRO) has done for green roofing—will help support the design of technically correct blue roof construction and provide information for specifiers, designers and installers.
What is a Blue Roof?A flat roof that is designed to retain water above the waterproofing membrane. Rather than allowing water to drain off the roof as soon as possible, a blue roof deliberately retains some or all of the water. It can then treat and release the water at a managed and controlled rate directly into sewers. waterways and river systems. There are a number of reasons why blue roofs are desirable:
- Urban flooding caused by storm water runoff is a significant problem in the UK, and Sustainable Urban Drainage Systems (SuDS) are a prerequisite in most new developments
- Storm water management can temporarily mitigate the impacts of rainwater runoffs, both on water volume and quality. Blue roofs control the flow by outlets at roof level or flow control device at a lower level
- Blue roofs are space savers which may be very attractive in contrast to providing attenuation at ground level in the landscape or within the building footprint