Mediating effects of ventilation on the impacts of temperature on human comfort, health and cognitive performance: A living lab study

• Moderate temperature and poor ventilation both decreased human comfort. • Cognitive performance was unaffected by moderate temperature or reduced ventilation. • Poor ventilation amplified the temperature impact on thermal comfort. • Temperature and ventilation interacted in perceived air quality, acute health symptoms, and potentially cognitive performance. The independent effects of increased temperature and reduced ventilation on human comfort, health, and cognitive performance are well documented. However, how ventilation moderates the impacts of temperature on humans remains underexplored. This living lab study investigated thermal comfort, acute health symptoms, physiological responses and cognitive performance under three experimental conditions: two suboptimal temperatures (24 and 27°C) and two ventilation scenarios (mechanical ventilation on at 215 m 3 /h and off). Sixteen subjects were exposed to each condition for 125 minutes in a balanced order. At 27°C, when the ventilation system was turned off, the mean CO 2 concentration increased from 800 ppm to 1,900 ppm. Subjects felt warmer and rated the thermal environment as less acceptable compared to the ventilated condition. The increase in mean skin temperature and decrease in core body temperature were further significantly aggravated. Compared to 24°C with ventilation, subjects reported greater fatigue and sleepiness and rated the air quality even worse, along with a declined trend in cognitive performance (P<0.05, d<0.5), even though no significant independent effects of increased temperature or reduced ventilation were observed within the short exposure duration. These findings suggest that ventilation mediates the effects of temperature, even within typical indoor ranges, and highlight noteworthy interactions between temperature and ventilation. These results support the revision of the current temperature and ventilation requirements in existing standards, particularly in the context of a warming world.