C050 -- Effects of Urban Heat Islands During Heat Waves in Montreal Residential Buildings PDF

Mesoscale meteorological simulations of the urban climate in Montreal during the hot summer of 2020 are used to assess the impact of the urban heat island on thermal comfort and building cooling energy demand in typical residential buildings. A new approach based on the cooling degree-hours (CDH) is proposed to map the urban heat island (UHI) of Montreal, called ‘cooling demand island.’ In the UHI of Montreal, the total cooling degree-hours are 30% higher compared to the rural surrounding, equal to an average increase of 15% in cooling energy demand. During the 2020 summer, non-air conditioned residential buildings experience more than 50% of the time thermal discomfort indoor. During heatwaves, the cooling energy demand increases substantially (more than 50%), since the air temperature during these periods is on average more than 10°C higher compared to non-heatwave days. Building energy demand simulations using reference climate data underpredict the cooling energy demand substantially compared to local climate data collected during hot summers. The analysis shows that local urban climate data during hot summers with heatwaves has to be used to properly predict the cooling energy demand of residential buildings in cities.