Analysis of Thermal Sensation: Evaluating Environmental and Subjective Factors, Using the ASHRAE Global Thermal Comfort Database II and SCATS Databases

Although thermal comfort in buildings is a crucial component in determining occupant well-being and energy consumption, it is impacted by a complex interaction between subjective and physical factors. Recent studies on indoor environmental quality have cast doubt on conventional static models by demonstrating how a person's thermal perception can be greatly influenced by their cultural expectations, acclimatization, and personal background. So, the aim of this study is to define to what extent do individuals from different countries, with varying cultural backgrounds and habits, perceive indoor thermal environments differently, considering environmental and subjective parameters. For this, the ASHRAE Global Thermal Comfort Database II and the SCATS database were used to identify potential patterns of thermal sensation and comfort perception across different countries. Data from office environments during the summer and winter was used. The environmental parameters considered to build the models were air temperature (ta), operative temperature (top), airspeed (vel) and relative humidity (rh) and the subjective parameters considered for the analysis were clothing insulation (clo) and metabolic rate (met). To examine the relationship between thermal sensation and both environmental and personal factors, a cumulative link model for ordinal responses was applied. In addition, a cumulative link mixed model was used to account for potential unobserved heterogeneity at the study level, particularly important given that the data were drawn from multiple independent studies. In total, eight different models were tested to determine the most suitable one for predicting thermal sensation votes. Additionally, different thermal comfort scenarios recommended by the EN 16798 standard were evaluated to account for variations in thermal perception among users from different countries. As a result, the most suitable model was the one that considers operative temperature, relative humidity, airspeed, metabolic rate, clothing insulation and country as predictors, where operative temperature and metabolic rate display strong positive associations with thermal sensation across both seasons, while airspeed shows significant negative effects, particularly in summer. Although relative humidity is also statistically significant, its influence on thermal sensation is weaker compared to other variables. Also, the shift in the influence of clothing insulation appears positively related to warmth in summer but negatively in winter. A comparison between countries for regional differences in thermal sensation was carried out. The inclusion of country as a categorical predictor in the thermal sensation models reveals clear regional differences in how participants from various locations experience and report thermal environments. During summer and winter, thermal neutrality is the most frequently predicted response across most countries, indicating a general tendency toward comfort under average conditions. These findings highlight the role of climate, building practices, and cultural norms in shaping thermal perception and underscore the limitations of static comfort standards when applied across diverse geographic contexts. This leads to variations among countries regarding the acceptability levels linked to standardized indoor conditions, showing the importance of air movement to make higher indoor temperatures more comfortable. However, the benefits of increased airspeed are influenced by users’ climate adaptation, with moderate airflow improving comfort in most cases but excessive velocities reducing acceptability in some regions.