Assessment and Mitigation of Overheating Risks in Archetype and Existing Canadian Buildings under Recent and Projected Future Climates

This research aims to develop a framework to assess and mitigate the overheating risks under projected future climates for both archetype and existing buildings. More specific objectives are to 1) determine the contribution and correlation of individual building envelope parameters to the change in indoor temperature in conjunction with ventilation, therefore, to determine whether high-energy-efficient buildings required by Canadian building codes to reduce heating consumption in new buildings are at lower or greater overheating risk compared to old buildings; 2) develop an automated calibration procedure to calibrate a building simulation model based on the indoor hourly temperature to achieve high accuracy to be used overheating studies in existing buildings; 3) assess overheating risks under current and future extreme years and recommend effective mitigation measures; and 4) provide an optimal design for retrofitting existing buildings to achieve lowest heating energy demand and highest thermal and visual comfort in new building design. To achieve these objectives, a robust sensitivity-analysis (SA) and calibration method, a systematic framework for evaluating overheating and passive mitigation measures, and an optimization methodology are developed and applied to an archetype detached-house and existing-school-buildings. 
\nThe results showed that the archetype and existing Canadian buildings have experienced overheating under current climates and the overheating risks will increase dramatically under future climates. Due to the positive contribution of lower U-values of windows, walls, and roofs and SHGC, high-energy-efficient houses have a lower overheating risk than old buildings if adequate ventilation (>2.2-ACH) is provided. Natural ventilation in the high-energy-efficient house is sufficient to reduce the overheating risk under the recent climate but will require adding interior and exterior shading under future climates. For existing-school buildings, the calibrated model achieved high accuracy. The results also showed that the use of exterior blind roll or a combination of night cooling and other mitigation measures that reduce solar heat gain is required under the recent climate and adding a cool roof will be required in future extreme years. For optimization design, the applied optimization methodology can generate several optimal building design solutions based on Window-Wall-Ratio.

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