Blue roofs

Schematic of flow control valve type blue roof/ rooftop detention

Blue roofs are ideal for:

• Sites without significant space at ground level for infiltration,
• Zero-lot line projects with outdoor amenity requirements

Ministry of Transportation do not permit blue roofs to form part of a SWM plan owing to concerns over long term maintenance; this affects relatively few projects. The concerns arise from instances where building operators have found outlet control structures blocked with leaves or other debris. Without understanding the purpose of the device, these have been removed to prevent recurrence of the blockage. A study in New York City found that a modular system of trays outperformed an outlet flow control device in stormwater management. It might reasonably be expected that a modular system would present fewer opportunities for complete failure from a single action, either through clogging or breakage of an storage element.

Providers

In our effort to make this guide as functional as possible, we have decided to include proprietary systems and links to manufacturers websites.
Inclusion of such links does not constitute endorsement by the Sustainable Technologies Evaluation Program.
Lists are ordered alphabetically; link updates are welcomed using the form below.

Flow control devices

• Watts Canada
• Zurn

Other

These products are designed to suspend green roof (or other) systems above a layer of free water for the detention period.

• Hydrotech
• Livegreen

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The temporary storage of stormwater to control discharge rates, and allow for sedimentation.

The slow movement of water into or through a soil or drainage system.

Penetration of water through the ground surface.

Stormwater Management

A thin layer of vegetation and growing medium installed on top of a conventional flat or sloped roof, also referred to as living roofs or rooftop gardens.