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In future years the frequency, duration and magnitude of extreme heat events, such as heat waves, is expected to increase due to climate change. The population is exposed to higher thermal discomfort and risk at home and, at the same time, high external temperatures make it more difficult to cool their household through natural ventilation.
In order to propose adaptive measures, research should first assess the thermal resilience of the existing residential buildings when exposed to prolonged heat stress. Poorly insulated and non-equipped buildings typical of Southern
European building stock are between the most affected typologies, suffering thermal discomfort both during mild winters and hot summers. The effect of torrid summers has been partly counterbalanced by vernacular control strategies adopted in the Mediterranean culture, such as natural cross-ventilation and solar shading devices.
However, the effectiveness of those strategies is in doubt due a combination of the widespread of building design depending on mechanical ventilation at the expense of passive control and the increase of summer temperatures.
The objective of this study is to analyse the thermal resilience of a reference building in Barcelona against extreme temperature events and assess its ability to maintain a comfortable and safe indoor environment through passive strategies. A Building Energy Model of an apartment in a multi-family building has been designed to dynamically incorporate vernacular control strategies, such as natural ventilation and solar shading, based on internal (occupancy) and external inputs (temperature and irradiance) acting as triggers.
The building is first simulated during the period surrounding the record-high heat wave which hit Catalonia in summer 2018, and then repeated using different input weather data, which correspond to a heat wave period detected under two future climate change projections. All simulations discerned between two types of occupants’ behaviours: aware and fixed. Occupants’ comfort is assessed according to the adaptive comfort model. Thermal risk is evaluated comparing the indicators of Heat Index and Humidex. The results have been assessed based on three main overheating and resilience metrics: the unmet hours, expressing the share of time spent in discomfort or risk conditions; the overheating intensity; and passive survivability indexes. The occupant control based on external temperature (Aware) provided around 2 and 5 ºC lower operative temperatures than a fixed schedule for natural ventilation (Night). Under future climate scenarios, the thermal risk values fall into the worst conditions using the fixed control, an occurrence avoided with aware ventilation. Considering the projected 2050 future scenario, the aware control reaches 18 nights above 28ºC and 9 nights above 30ºC while the fixed control counts with 38 and 91 nights, respectively.