Indoor and outdoor thermal comfort differences and pathways to climate shelters during heat waves in a neighborhood of Lisbon

This study addresses heat stress in a Lisbon neighborhood, focusing on the differences in indoors and outdoors thermal comfort conditions, and identifying optimal paths to climate shelters during heatwaves. Heat events, especially in early summer, pose significant health risks, particularly for vulnerable groups like the elderly, who are more susceptible to respiratory and cardiac issues. With Portugal's aging population, the number of elderly living alone is rising, making it urgent to improve adaptation strategies to excessive heat. Conducted in the summer of 2022, the study monitored thermo-physiological outdoor conditions and those in twenty indoor dwellings. Results revealed notable temperature disparities: indoor nighttime temperatures were 5.6°C cooler than outdoors, while daytime was only 2.3°C. Indoor environments had a smaller thermal range (1.0°C) compared to the 10.0°C fluctuations outside. This limited cooling capacity highlights the challenge for vulnerable populations without air conditioning. The study also modeled thermal comfort in nearby gardens, proposing green infrastructure and water bodies as potential climate shelters. These shelters provide cooling through the evapotranspiration process and shaded areas. However, it is essential to consider other fundamental dynamic factors such as wind speed, radiative heat, and physical exertion, which are crucial for adapting to heat in real-world, active conditions. Using micrometeorological models, the research simulated the temperature of a typical summer day, highlighting the role of shade and green infrastructure, such as tree cover, and identified the optimal routes to these shelters for individuals whose homes are unable to cool down during the day. Ultimately, the findings aim to improve recommendations tailored to real-time conditions and individual needs, enhancing urban resilience against escalating heatwaves and helping safeguard vulnerable populations from the harmful effects of extreme heat.