Evaluation of thermal resilience to overheating for an educational building in future heatwave scenarios

Airtight and highly insulated buildings are subjected to overheating risks, even in moderate climates, due to unforeseeable events like frequent heatwaves and power outages. Educational buildings share a major portion of building stocks and a large percentage of the energy is expended in maintaining thermal comfort in these buildings. Overheating risks in educational buildings can lead to heat-stress and negatively impact the health conditions and also cognitive performance of the occupants. In the light of increasing severity and longevity of heat waves in future climate scenarios, and associated power outages occurring during the heatwaves, measures to reduce overheating risk while limiting the cooling energy is gaining importance. Since the performance of existing buildings are not guaranteed during events like heatwaves, power outages, it is crucial for these buildings to be resilient to overheating. (Building) resilience is a method to deal with these uncertainties and is stated as “an ability of the building to withstand disruptions; and to maintain the capacity to adapt, learn and transform.” The focus of this paper is to evaluate thermal resilience for two test lecture equipped with low-energy cooling strategies like natural night ventilation (NNV) and indirect evaporative cooling (IEC) rooms, by dynamic Building Energy Simulations (BES). To assess the thermal resilience to overheating  three different heatwaves (HW) files ( intense,  severe, and longest) for 3 future scenarios (1) Historical (2010-2020), (2) mid-term (2041 -2060) and (3) long-term (2081-2100) and a 24h power outage (PO)scenario was simulated. Benchmarking was done with a base case- Typical Meteorological year(TMY) with no power outage. The heatwave files were developed adopting the methodology proposed by the 'Weather Data Task Force’ of International Energy Agency Energy in Buildings and Communities Programme (IEA EBC) Annex 80 “Resilient Cooling of Buildings”. This study shows, IEC has high to moderate recovery capacity in TMY period and low recovery capacity in HW period, for a power outage of 24 h.  Recovery capacity is low during HW period, especially during an intense and longer HW period when outdoor temperature influences the cooling capacity of the IEC. The results also demonstrates the impact of the thermal mass on the resilience to overheating. Passive survivability assessment indicates, the lecture room with lighter thermal mass does not violate 30℃ threshold during a power outage in TMY period and additionally,. recovers faster (11% times faster) from peak temperature compared to lecture room with heavy thermal mass. There is a steep increase in unmet degree hours (occupied hours above24℃ threshold) during HW compared to TMY period.  This paper gives a directive towards assessment of resilience to overheating  and also points out the gap in the existing indicators to assess the resilience.