Exploring Thermal Environment Assessment via Physiological Parameters in a Decreasing Thermal Ramp

The analysis of thermal comfort has increasingly focused on the role of occupants, aiming to create environments tailored to their needs while minimizing energy waste. The human-centric approach has been achieved through research into physiological parameters and subjective environmental assessment.

The present study aimed to investigate which and to what extent physiological factors and subjective responses are correlated in the dynamic thermal environment due to changes in air temperatures. The data were collected during a winter 2023–2024 through a study, which originally focused on the willingness to pay for a thermally comfortable environment. The experiment involved 36 participants in two 4-h sessions in a room simulating office. During each session, a decreasing thermal ramp was applied continuously, ranging from 23 °C (±1.2 °C) to 17 °C (±2.8 °C). Meanwhile, the skin temperatures (SK) at three points on the body (chest, forearm, and shin) and heart rate variability (HRV) were continuously measured together with the environmental parameters while the thermal sensation (TSV), thermal comfort (TCV), and thermal acceptance (TAV) were collected every 30 min. Concerning the subjective thermal assessment, the most correlated physiological variable was SK_mean (p < 0.05), while the least correlated was the low-high frequency (LF/HF) ratio. The correlation coefficients of SK_mean were 0.445, −0.331, and −0.321 with TSV, TCV, and TAV, respectively. Conversely, the mean LF/HF ratio showed weaker correlations of 0.029, −0.009, and −0.023 with TSV, TCV, and TAV, respectively. However, the HRV factor was not statistically significant.