Impact of heatwaves and system shocks on a nearly zero energy educational building : is it resilient to overheating?

The characteristic that describes the extent to which buildings and their systems maintain their performance during shocks is called resilience. Building policies in the EU have already addressed the resilience of buildings against possible hazards (i.e., natural disasters, extreme weathers, fires). However, with increasing overheating risks (e.g., climate change) accompanied by their detrimental health and economic impacts, the thermal per-formance of nearly zero energy buildings (nZEB) is not guaranteed. This study aims to assess the impact of shocks and combinations on the thermal resilience of educational nZEB against heatwaves (HW) and system shocks (SS) including failure of indirect evaporative cooling (IEC), natural night ventilation (NNV) and solar shading failure (SF). A Modelica model of the building was developed and experimentally validated. Shocks were classified and quantified using the novel normalized degree of shock (doS) index. Heatwaves (HWs) had 20 x to 93 x more critical impact than the worst SS (NNV failure). Additionally SS occurring at the start of the operational period is 1.2 x more critical than SS occurring later in the day as it allowed for significant heat build-up in both class-rooms. In future climate scenarios a combination of HWs and power outages will become frequent. This study showed that a combination of a full day of cooling strategy and shading failure occurring on the hottest day of a 6-day long HW, is 10% more critical on both lecture rooms than an individual 10-day long HW. Classroom with heavy thermal mass prolongs the absorptivity of the shocks but delays recovery.