The concept of comfort, indicating a well-being, is challenging to define in a consensual and objective manner. One approach can be to circumscribe this concept in terms of environmental conditions that are optimal for the execution of a given activity.

Paris region's degraded oceanic climate is characterised by seasonal fluctuations in temperature, with pronounced variations between hot days and cool nights during summer. The classification of this climate as 'moderate' signifies that indoor thermal conditions are deemed to be safe for occupants.

he regulation of the indoor thermal environment is a multifaceted process, encompassing the implementation of external solar protection measures, a function significantly enhanced by the presence of insulation. Additionally, the process entails the nocturnal evacuation of heat through the act of opening windows. The air renewal rate is therefore a key factor in avoiding exposure to heat-related health risks, with wind strength and temperature difference acting as the primary drivers of this rate.

The two parameters are found to be significantly impacted by the urban heat island (UHI) effect in comparison with rural areas, or by the presence of urban parks, contingent upon prevailing atmospheric conditions.

Using observed data on wind speed and temperatures in the city, the consequences of the UHI on the indoor thermal environment are calculated for a dwelling representative of social housing in Paris after renovation.

The sensitivity study on wind and temperature facilitates the identification of conditions under which the UHI significantly undermines the protective function of the building envelope against heat. Furthermore, the impact of the UHI on night-time temperature can be used to adapt ventilation strategies during nocturnal hours, thereby optimising the dissipation of internal heat. Furthermore, the identification of risk factors associated with urban planning, such as distance from vegetated areas or the presence of water (rivers), is enabled.

How to cite: Sabre, M., Alessandrini, J.-M., Lemonsu, A., Nagel, T., Roccamena, L., and Wei, W.: Influence of the ICU phenomenon on the thermal conditions of the indoor environment during hot periods, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-451, https://doi.org/10.5194/icuc12-451, 2025.

Climate change is causing an increase in heat exposure, resulting in heat stress with negative effects on health and work capacity. As people spend most of their time in buildings, indoor thermal conditions are of special relevance. Elderly people with acute illnesses and pre-existing conditions are particularly vulnerable to heat stress, making hospitals an area of high concern. This study assesses indoor heat stress occurring from May 15 to September 30, 2023 in the University Hospital Freiburg, Germany, based on indoor measurements of air temperature and the physiologically equivalent temperature (PET). The indoor measurement data used in this study were collected by a network of low-cost sensor systems termed “Mobile Biometeorological System” (MoBiMet). Data collected in 60 rooms of varying use across eleven hospital departments were analysed. Heat stress was evaluated in terms of location, frequency, and intensity, as well as in its relation to outdoor temperatures, allowing for the subsequent identification of vulnerable hospital areas and functions. Slight heat stress was the most frequent thermo-physiological stress level, and occurred in all studied rooms, with 49 rooms showing additional moderate heat stress and 17 rooms showing strong heat stress. Heatwaves were identified as temporal heat hotspots due to high levels of heat stress and limited night-time cooling. Spatial heat hotspots were found in rooms without windows or air conditioning, located on higher floors in buildings constructed between 1950 and 1990. Inpatients spending the night in the hospital during heatwaves and physically active staff are particularly vulnerable to heat stress. To improve the health and wellbeing of patients and staff and ensure hospital functionality, possible short- and long-term measures for prevention and relief are recommended.

How to cite: Matzarakis, A., Epp, K., Sulzer, M., Steinmann, D., Zeeman, M., and Christen, A.: Human-Biometeorological Assessment of Indoor Heat in Freiburg’s University Hospital in Summer 2023, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-42, https://doi.org/10.5194/icuc12-42, 2025.

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.

How to cite: Manuel Saraiva Lopes, A., Viljoen De Vasconcelos, J., Fragoso, M., Oliveira, A., Matias, M., Silva, T., and Reis, C.: Indoor and outdoor thermal comfort differences and pathways to climate shelters during heat waves in a neighborhood of Lisbon, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-323, https://doi.org/10.5194/icuc12-323, 2025.

Canada has experienced a warming trend since the industrial revolution, surpassing the global average by a factor of two, with its northern regions experiencing an even more pronounced threefold increase in temperature. This significant and consistent shift in climate has led to extensive alterations in climate patterns nationwide, intensifying the frequency, severity, and duration of climate-related natural disasters such as floods, wildfires, and heatwaves. Canadians typically spend 90% of their time indoors in various residential, commercial, and institutional structures. Thus, enhancing the resilience of these buildings and preparing them for anticipated climate changes is crucial for maintaining the well-being of the Canadian population in the face of a changing climate. To design buildings and to assess building performance against the varying outdoor climate over their lifespan, the National Research Council Canada (NRC) has developed novel methods to prepare future projected climate datasets incorporating the effects of climate change, as well as urban heat islands. Furthermore, potential cooling which can be achieved by implementing city-scale nature-based solutions such as increased greenery and albedo, are also simulated and integrated into the climate datasets. In this paper, the approach and key aspects of aforementioned building simulation climate data will be provided. The NRC are currently using these files to incorporate climate resilience and nature-based solutions into building designs under the Government of Canada's Climate Resilient Built Environment Initiative.

How to cite: Gaur, A.: Buildings design climate datasets for Canadian cities incorporating potential effects of climate change, urban heat island, and nature-based solutions, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-421, https://doi.org/10.5194/icuc12-421, 2025.

Zero-Energy Buildings (ZEB) and Zero-Energy Houses (ZEH) are designed to reduce energy consumption using high-efficiency equipment and highly insulated envelopes. ZEHs are expected to enhance the indoor thermal conditions in winter, reducing the health risks associated with low temperatures. On a larger scale, ZEB/ZEH implementations in urban areas can influence outdoor temperatures by reducing building exhaust heat and heat retention in the building structures. Despite these potential benefits, few epidemiological studies have evaluated the effect of temperature on heat-related health risks. This study aimed to quantify temperature changes and their impact on heat-related mortality risk when ZEB/ZEH is adopted city-wide in 23 wards of Tokyo. Using an urban meteorological model and an environmental epidemiological model, the study set ZEB/ZEH performance to government benchmarks. Findings indicated that the average urban temperature in August remained stable during the day but decreased by 0.1–0.3 °C from night to early morning. This decrease was largely due to reduced air-conditioning exhaust heat, decreased heat storage in building frame, and the emission of cold heat from heat pump water heaters. When these results were applied to an epidemiological mortality risk prediction model, the risk of heat-related deaths in August was reduced by over 8 % across all 23 wards. This reduction is comparable to the effect of a significantly increasing green coverage in the area. Approximately half of the risk reduction was attributed to the cold heat from the heat pump water heaters.

How to cite: Yamaguchi, K., Takane, Y., and Ihara, T.: Impact of zero energy buildings and houses on urban thermal environment and heat-related mortality risk, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-142, https://doi.org/10.5194/icuc12-142, 2025.

Building retrofitting can reduce energy consumption and greenhouse gas emissions. The impacts of enhancing building thermal performance (e.g. improve insulation and air tightness) extend beyond individual buildings via altered anthropogenic heat emissions from buildings (Q_F,B) to the outdoor climate. These dynamic feedbacks have been widely explored for summertime heat mitigation, but outdoor air temperature impacts from wintertime urban canopy changes in Q_F,Bare little studied.

Here, we couple a neighbourhood-scale urban climate model (SUEWS) and a building energy model (EnergyPlus) to evaluate the impacts of building energy retrofitting on outdoor thermal environment across 16 US climate zones. The results show energy retrofitting exacerbates the nighttime overcooling and change the boundary layer stability due to reduced Q_F,B. This cooling effect is more pronounced in areas with low wind speeds (i.e. seasonal median ≤ 0.5m s^-1) and higher aerodynamic resistance (e.g. Denver and Albuquerque), causing nocturnal temperatures to drops by >1.5℃. Whereas, with higher wind speeds (e.g. New York and Buffalo) there are much smaller temperature decreases and less periods with stable condition. These findings highlight the challenge of balancing building energy savings with impacts on the outdoor thermal environment and demonstrate how background climate shapes the influence of building design and operations on urban climate.

How to cite: Liu, Y., Luo, Z., and Grimmond, S.: Winter nighttime overcooling and atmospheric stability changes resulting from building energy retrofit, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-418, https://doi.org/10.5194/icuc12-418, 2025.