Heatwaves

The increasing severity and duration of climate change is that extremes – notably heatwaves, increases the risk of human thermal stress in indoor environments where people spend most of their times. Recent field measurements have demonstrated significant overheating in the EU building stock in the EU, characterized by well-insulated and air-tight envelopes. This exposes vulnerable communities to increases mortality risks that is bound to only get worse with an ever-worsening climate warming.

The increasing frequency and intensity of heatwaves highlight the necessity for resilient building design to reduce heat-stress-related discomfort and mortality among occupants. "Thermal resilience" refers to a building's capacity to endure thermal disruptions, maintain habitable conditions, and return to its intended state. This study aims to develop a thermal resilience indicator to make resilience an actionable concept for architects and HVAC engineers to assess and improve thermal resilience of buildings to overheating.

This study examines the impact of heatwaves on indoor operative temperatures of dwellings in Pamplona (north of Spain) and presents a comparative analysis of a typical summer and two extreme summers with heatwaves in 2003 and 2022. The assessment was conducted in two neighbourhoods with different urban morphologies and built periods related to different energy regulations in Spain. EnergyPlus was used to simulate each residential typology for 5 months in 8 different orientations and with the constructive characteristics that correspond to its built period.

Airtight, highly insulated, and passively cooled buildings in the EU are designed under typical outdoor and indoor thermal conditions. With increasing risk and uncertainty with regards to climate change and associated heatwaves(HW), the design thermal performance of these buildings is not guaranteed. It is crucial to focus on improving thermal resilience to overheating and futureproof these buildings. “Thermal resilience to overheating” is the characteristic that describes the extent to which buildings and their cooling strategies can maintain habitable conditions during or post shocks.

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 context of climate change, Building Performance Simulations are used to assess the ability of passive buildings to maintain acceptable comfort conditions, or to limit the air conditioning energy consumption during heatwaves. Climate projection data, including heatwaves, are needed to feed the Building Performance Simulation tools. A building, located in a given location, is likely to experience several heatwaves with different characteristics in the coming decades.