Ecoroof and WRF Model Evaluation for Canadian Climate Model Development

Green roofs can mitigate urban heat, reduce building energy use, reduce stormwater runoff and contribute to biodiversity and urban livability. To effectively evaluate their impact, green roofs must be incorporated into urban climate models, where reliable green roof models provide critical surface boundary conditions for city-scale adaptation simulations. Consequently, it is essential to test these models to ensure accurate and dependable results.

This research evaluates two green roof models—EnergyPlus’ Ecoroof module and the model embedded in the multi-layer urban scheme within the Weather Research and Forecasting (WRF) model—to determine their effectiveness in simulating the green roof energy balance for Canadian climate conditions. Specifically, we investigate: (1) which model more accurately simulates green roof energy balance and (2) the key parameters driving differences in model outputs. Using observations collected from a green roof test array in London, Ontario, during the summers and autumns of 2014 and 2016, the modeled surface temperature (T_surf), latent heat flux (Q_e) and soil heat flux (Q_g) are evaluated through statistical analyses and sensitivity assessments.

Preliminary results from the EnergyPlus model for Q_e, Q_g and T_surf show overall index of agreement (d_r) values of 0.59, 0.69 and 0.78, respectively, with variability between years. The tested periods in 2014 show higher d_r ranges for all variables—0.50 to 0.81 for Q_e, 0.60 to 0.70 for Q_g, and 0.72 to 0.90 for T_surf —while 2016 exhibits lower d_r values, with some periods dropping below 0.50 for Q_e and T_surf. Key parameters influencing the model’s performance include LAI, minimum stomatal resistance, soil specific heat, soil thickness, and soil water content. These findings support integrating green roof models into urban climate frameworks, highlighting their role in heat adaptation and sustainable design.