Human-Biometeorological Assessment of Indoor Heat in Freiburg’s University Hospital in Summer 2023

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.