The Influence of Thermal Disposition on the Thermal Comfort of Users of Mixed-Mode Buildings in a Subtropical Climate

The main objective of this study is to investigate how thermal disposition influences the users’ perception of thermal comfort in mixed-mode buildings in a subtropical climate. A total of 1,032 responses from heat-sensitive users and 733 from cold-sensitive users, collected via electronic questionnaires, were analysed. The average PMV (Predicted Mean Vote) for both groups were 0.11 and 0.26, respectively, both within the thermal comfort zone defined by ASHRAE 55 (-0.5 to 0.5). However, analysis of subjective responses (AMV − Actual Mean Vote) revealed significant variations within this theoretical comfort range, indicating limitations of Fanger’s model in accurately representing the real comfort perception of users with different thermal sensitivities. The correlation between PMV and AMV was stronger among cold-sensitive users, especially during air-conditioning use (R² = 0.22), compared to natural ventilation use (R² = 0.10). In contrast, the heat-sensitive group showed coefficients of determination equal to 0.13 during natural ventilation use and 0.16 during air-conditioning use. Additionally, it was found that even in environments classified as comfortable according to ASHRAE 55, the PPD (Predicted Percentage of Dissatisfied) exceeded the 10.0% limit set by the standard, reaching approximately 30.0%. The results suggest that the PMV/PPD model, which is based on a population average approach, often underestimates or overestimates actual thermal discomfort, especially in naturally ventilated spaces or those with high thermal variability. Therefore, it is concluded that incorporating subjective factors, together with the application of adaptive models, is essential for a more accurate assessment of thermal comfort in mixed-mode buildings.