Green Envelopes: Contribution of Green Roofs, Green Facades, and Green Streets to Reducing Stormwater Runoff, CO₂ Emissions, and Energy Demand in Cities

The research focuses on the environmental benefits derived from an overall intervention of green envelope types [roofs, façades and streets] in the city core of Vancouver, Canada. To achieve this, it analyzes previous precedents conducted in cities such as Berlin, Germany; Malmö, Sweden; Toronto, Vancouver, Canada; Chicago and Seattle, USA; and applies the data to a particular case study area in Downtown Vancouver. It then applies the Seattle Green Factor to the case study area, and quantifies the contribution of the green envelope interventions in order to ameliorate environmental impacts in terms of reducing stormwater runoff, CO₂ emissions, and energy demand by buildings. Calculated results from the case study area shows that the addition of green roofs, green façades and green streets would reduce stormwater runoff up to 13% (4% by green roofs, 3% by green streets and 6% by green façades), reduce building energy demand by 9%, and CO₂ emissions by 12%. With these findings, the paper proposes a new Vancouver Green Factor for the selected area, which introduces new concepts to these types of green factors, such as the volumetric value of urban surfaces.