The Effect of Time of Day and Time of Year on Thermal Comfort

Abstract

In order to determine if affective responses to cool, neutral, and warm temperatures were related to the season of the year and the time of day, 108 subjects were exposed in groups of six (3 males and 3 females) for 3 hours to three temperatures 20.0°C, 25.6°C and 31.7°C at 50%rh during the morning (0900–1200) afternoon (1300–1600) and evening (1800–2100) in the summer and winter. The subjects were sedentary and wore similar clothing; a 9 category Thermal Sensation ballot and a 7-pair semantic differential scale for measuring Thermal Comfort were administered every half hour during the three hour exposure. An analysis of variance showed that the main effects, Time of Day, Sex and Season were not significant and only Temperature and Voting were significant; both measures showed significant Season x Temperature interactions. Basically, the 20.0°C environment was judged to be more comfortable in the summer than in the winter and the 31.7°C environment was judged to be more comfortable in the winter than in the summer. The seasonal findings are opposite to those found in recent research and suggest that different temperature criteria for thermal comfort should be considered for summer and winter conditions.