Building a Smart Blue Roof

We’re building a smart blue roof system and upgrading the rainwater harvesting system at our head office building. Once construction is complete, we’ll be able to assess the real-world performance of the system and understand how to scale this technology in the local industrial, commercial and institutional sector and in communities across Canada.

Benefits of Smart Blue Roofs

Smart blue roofs can be built on top of flat-roofed buildings common in the commercial, industrial and institutional sector which make up approximately 20 – 30 per cent of total urban areas. Using real-time weather information, smart blue roofs control the release of rainwater in three ways:

  • Hold rainwater until it evaporates from the rooftop, also providing evaporative cooling benefits
  • Send rainwater to a harvesting tank where the water can be reused
  • Slowly release rainwater into the municipal stormwater system

Smart blue roofs are a form of green infrastructure (GI). GI are sustainable technologies and practices that manage rain to reduce the risks of flooding, protect water quality in streams and build resilience in a changing climate.

With increased risk of flooding due to more extreme and unpredictable rainfall patterns across Canada, there is a greater need now for innovative approaches to stormwater management, particularly in highly urbanized areas. The concept of smart blue roofs has emerged for greater stormwater management potential and benefits compared to vegetated green roof systems. Piloting and implementing a smart blue roof at CVC’s office will allow us to determine and report on the actual costs and benefits of such an innovative system.

Project Phases

In 2017, CVC received $175,000 in federal funding from the Federation of Canadian Municipalities to assess the technical and financial feasibility of implementing a smart blue roof on our administrative office as well as its scalability in the broader industrial, commercial and institutional sector where large, flat-roof buildings are common.

Key findings include the following:

  • The building has a parapet height of 400 mm. Structurally, the rooftop can hold up to an average of 130 mm of precipitation (equivalent to 40m3 across the roof area) thus capturing the 100-year storm.
  • The smart blue roof system can meet non-potable water demands of 8.84 m3/day, exceeding our building’s current non-potable water demand of 5.68 m3/day.
  • By storing water on the roof, a typical air conditioning unit will see a reduction of 11.6 GJ/year translating into an annual electricity savings of 3,210 kWh, or about $302 and a GHG reduction of about 0.2 tonnes CO2e annually.
  • The estimated cost to implement a smart blue roof on CVC’s Building A roof is $365/m2.

In July 2020, CVC received over $280,000 in funding through an Intact Adaptation Action Grant from Intact Financial Corporation to build and evaluate the performance of a smart blue roof system at CVC’s head office.

Between August 2020 and December 2021, together with Enviro-Stewards Inc., Interpump Ltd. and WSP Inc. consultants, we finalized a smart blue roof design and upgrade to the rainwater harvesting system. In January 2022, the City of Mississauga approved CVC’s building permit application.

The smart blue roof will be equipped with the following main components:

  • A water-proof segregation barrier segregating the smart blue roof area from the remaining roof section
  • A set of new emergency overflows complementing the exiting four roof drains
  • A set of flow control modulating automatic valves responsible for delivering rainwater to the basement cistern
  • A new set of secondary emergency overflow scuppers
  • Monitoring and control equipment, including level sensors, temperature sensors and flow meters
  • A set of bird-landing control devices
  • A complete rainwater recirculation and treatment system to be located in the existing third floor mechanical room.

Project construction is set for spring 2022. The construction project team consists of CVC, Enviro-Stewards Inc., Interpump Ltd., Firenza Plumbing and Heating Ltd., and WSP Ltd.

Construction will occur in three stages:

  1.  Rooftop Blue Roof Work
  2.  Third Floor Water Recirculation and Treatment System
  3.   Basement Rainwater Harvesting Upgrades

Some key performance indicators that will be monitored once the smart blue roof and rainwater harvesting system is commissioned are:

  • Total volume (m3) of stormwater removed from the storm sewer system
  • Total peak flow reduction (m3/s) to storm sewer system
  • Estimate savings on the annual stormwater charge
  • Estimate annual water savings from rainwater reuse
  • Estimate annual energy savings from rooftop evaporative cooling

Other questions of interest that will be explored are:

  • How does building scale stormwater management benefit both the landowners and the municipality?
  • What is the cost to operate a network of blue roof systems that provide the equivalent stormwater control as a stormwater pond retrofit?

We look forward to sharing results and lessons learned with our project partners and the broader community once the system is operating.

Project Partners

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