Energy savings potentials of commercial buildings by urban heat island reduction strategies in Montreal (Canada)

• Energy savings in using reflective materials for the skin of commercial buildings is as high as 11%.
• The effect of temperature decrease in urban areas, by increasing the albedo, on energy consumption of buildings is significant (up to 4%).
• Snow on the roof reduces the winter penalties of the albedo enhancement.

The energy consumption of commercial buildings in Montreal (Canada) with absorptive and reflective skin materials is investigated. Four building prototypes (small office, medium office, large office, and retail store) with two types of heating systems (gas heating and heat pump) categorized based on vintage and HVAC system (old building with old HVAC, old building with new HVAC, and new building with new HVAC) are studied (total of 24 cases). For each case three simulations are performed using DOE-2 building energy model: (1) dark roof and walls with measured weather data: representing the actual case and the basis for comparing the effect on albedo enhancement, (2) cool roof and walls with measured weather data: determining the direct effect of increasing albedo of an individual building, and (3) cool roof and walls with modified weather data: predicting the effect of albedo enhancement in urban scale that contributes to weather condition. In all cases the effect of snow on the roof is considered and for modification of the weather data output of mesoscale meteorological simulation is used. Calculated energy consumption and energy expenditure showed that, in general, increasing the reflectivity of building skin saves energy and money. The surface modification is more beneficial for old vintage buildings. The maximum expenditure savings is about 11% for buildings with dark roof and walls, where the contribution of urban-scale increase in the surface albedo can be as high as 4% in the total energy expenditure savings.