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Published on 12 January 2020 16:03

Blue Roofs: What are they and how are they used

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Key Learning outcomes
  • What a Blue Roof is
  • Why and when they need to be specified
  • The importance of calculations
  • The components of a blue roof system
  • Safety aspects to be aware of
Rainwater management has become a key consideration as part of building design processes. This is due in part to changes in the way we receive rainfall in the UK because of climate change, but also because of increased areas of hardstanding impermeable surfaces and landscaping.

Green roofs are already known for their ability to attenuate water, but this can now be enhanced with blue roof technology. Here the roof not only stores water but is also able to delay water discharge after a high intensity rainfall event and release it at a pre-determined rate. This topic will look at how this can be achieved practically and why this type of specification is likely to become more commonplace in the future.

1.0 What is a Blue Roof?


A Blue Roof can be created at either roof level or on a podium deck and is suitable for both warm and inverted roof applications. It should be designed to attenuate water for defined period after the end of a defined maximum rainfall event, typically 24 hours, and to discharge water at a predetermined rate through controlled rainwater outlets. It will have a void within its build up to store storm water and a surface finish which can either be a green roof build up or porous hard landscaping.

The key to a successful Blue Roof application is design, both in terms of the roof construction itself and the drainage outflow parameters for the site. The following is a summary of items to consider when a Blue Roof is proposed.

When specifying a blue roof, the message is not to improvise; the penalty for getting it wrong could be catastrophic. Although not an official requirement, it’s not advisable to mix products from different sources but instead to use a complete system from one manufacturer if possible. It can also be beneficial to have the aid of a blue roof specialist, possibly from the manufacturer who can assist with design calculations using relevant rainfall data for the project location.

Most blue roof solutions, although designed to provide a similar end result, differ in their construction so it is very important for anyone carrying out installation to have received training for the specific system beforehand.
A blue roof is designed to store a large amont of rainwater for a given period of time and then release it slowly into the local surface water drainage system
A blue roof is designed to store a large amont of rainwater for a given period of time and then release it slowly into the local surface water drainage system
 
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