Assessing and mitigating overheating risk in existing Canadian school buildings under extreme current and future climates

•A framework is developed to assess overheating in existing building in whole summer.•Calibration simulation model is used using field measurements of indoor temperature.•Overheating risk in existing school building is assessed.•Climate change effect is studied using current and future extreme RSWY years.•Effective passive mitigation measures are provided for future extreme climates.