Programs: Building science, Environmental Planning, Civil engineering
Connected Blue-Green Roof (BGR) systems are engineered systems that overcome the deficiencies of green roofs through enhanced water detention and retention that regulate peak storm water flows and enable extended passive capillary irrigation. As such, BGR systems are a novel nature-based solution for climate change adaptation and mitigation that provides multiple benefits to the urban environment, including: water storm water management, heat island mitigation, carbon absorption, and restored biodiversity. They also provide added thermal mass to help regulate the temperature of buildings. A blue-green Vancouver roofscape has the potential to transform the city environment through its roofs.
In collaboration with the Green Infrastructure Department at the City of Vancouver, four experimental roof modules were designed and built at the “Helena Gutteridge” Plaza, just beside the Vancouver city Hall. These roofs are representative of a conventional roof (CR), a green roof (GR), a blue roof (BR), and a connected BGR system. The hydrological and thermal response of these roofs to the local weather is being monitored since the fall of 2019. For this purpose, the roofs were instrumented with water runoff sensors, temperature sensors to monitor the roof thermal profile, moisture content sensors for the GR and the BGR systems, and a water level sensor to monitor the level of water at the BGR retention/detention layer. A nearby meteorological station monitors local rainfall.
Key benefits to the City of Vancouver’s mission include:
- Beautifies the HG Plaza by adding greenery and interest
- Increases the comfort of this unshaded section of the plaza by cooling the area through evaporation and evapotranspiration
- Educates the public on green infrastructure and the City of Vancouver’s actions to meet the Greenest City Goals
- Builds the partnership between City of Vancouver and BCIT
- Supports the Council Resolution for Planning, Urban Design, and Sustainability to develop a green roof policy by informing the design criteria in the policy and helping to define the beneficial outcomes of the policy
- Supports the City of Vancouver’s water conservation goals by demonstrating a green roof design that requires less irrigation as well as reduced coolant tower water use through thermal insulation.
- Supports the City of Vancouver’s Rain City Strategy by demonstrating green roof designs that retain more rainwater volume which is good for the water quality of the City’s recreational waters and contributes to the resiliency of the City’s aging sewer system.