Optimizing Green Roof Design Parameter and Their Effects on Thermal Performance under Current and Future Climates in the City of Toronto

Buildings contribute 30% of total energy consumption worldwide and account for 28% of CO2 emissions. Green roofs (GRs) have shown potential in reducing cooling and heating loads of buildings, and thus, the related carbon emissions. This research aimed to analyse the thermal performance of extensive GRs compared to conventional roofs using three design parameters: GR growing media (GM) depth, Leaf Area Index (LAI) and thermal insulation thickness under current and future climates in Toronto, Canada. EnergyPlus was used to model the GR for three building archetypes of secondary school, office, and hospital. In addition, precipitation data for current and future climates was generated to account for GR moisture input. Results show higher GM depth, and LAI provides the highest annual energy savings for uninsulated GRs. However, at highly insulated roofs, the GR thermal performance is impacted and depending on the building type, the GR may require higher energy consumption.