Comparison of psychophysiological responses and cognitive performance between radiant- and air- based systems at varied temperature and ventilation conditions: A living laboratory study

Radiant-based systems are often assumed to provide superior thermal comfort over air-based systems, yet the evidence remains unclear. Moreover, how these systems affect comfort and cognitive performance under varying temperature and ventilation settings is still under investigation. To address these knowledge gaps, we conducted a study in which sixteen subjects experienced six experimental conditions in the HiLo living laboratory. These include two temperatures (24 and 27 °C), established by either a thermally activated building system (TABS − a radiant-based system) or a hybrid variable refrigerant flow system (HVRF − an air-based system). Two ventilation scenarios were tested using an independent mechanical ventilation system (on vs. off). Each condition was experienced by four subjects at a time for 125 min in a balanced order. Skin temperature, core body temperature, and heart rate and variability were continuously monitored. Mental arithmetic ability, executive function, and logical reasoning tasks were used as measures of cognitive performance. Thermal comfort, perceived air quality, sick building syndrome symptoms, and fatigue were rated by the subjects. While a few significant differences in human responses between TABS and HVRF were observed, the effect sizes were small (d < 0.5), and the patterns were inconsistent across different temperature and ventilation conditions. These results suggest that air-based systems can provide comfort levels comparable to radiant-based systems. When the environmental conditions are equivalent, cognitive performance remains unaffected by the type of system used.