Assessing Thermal Resilience To Overheating In An Office Building

Overheating has become a recurring problem in airtight and highly insulated buildings even in moderate climates. This study aims to analyze thermal comfort and thermal resilience in an office building during summer and mid-seasons by means of dynamic simulations. Thermal comfort assessment shows, this office building without improvements has a ‘good’ indoor climate for 79.6% of total occupied hours. However, the results also confirm that the office building will suffer from overheating during summer with full occupancy (primarily during afternoon when the outdoor temperature > 16°C). Simulations and on site measurements indicate, in winter and midseason (Temp < 16°C), there is no overheating. Two existing indicators of thermal resilience are assessed in this study, namely-(a) Thermal autonomy and (b) Passive Survivability. It has been demonstrated that the case study building has low threshold for both the resilience indicators. The office building has a low thermal autonomy to overheating in its current status (17.4%) due to low thermal mass,high heat gains and relying on the cooling and ventilation system to mitigate overheating risk rather than relying on the building and system parameters. This can be improved to 61.7% with additional natural ventilation of 5 ACH. For passive survivability, the temperature of Workplace 1 remains below 30℃ only for 8 hours when the power is switched off for heating and cooling, without sun shading or natural ventilation. This can be improved up to 12 hours with sun shading and natural ventilation. Thus, Passive survivability of the building is also low. This study demonstrates cooling and solar shading are indispensable to mitigate overheating in buildings. However with the addition of natural ventilation during day and night ventilation, good thermal comfort can be achieved for 86.1% of occupied hours.