Thermal comfort and adaptation in semi-outdoor environments

Designing semi-outdoor environments such as atria or open-style cafes is a popular technique in modern architecture to provide occupants with natural outdoor elements in an artificial environment. Occupants are likely to expect a thermal environment differing from the indoors, and thermal adaptation is expected to play a major role in achieving comfort. Seasonal field surveys were conducted in four semi-outdoor environments for short-term occupancy with different levels of environmental control. Observations were made on occupancy conditions and clothing adjustments. Sets of 2,248 questionnaires and corresponding thermal environmental data were also collected throughout the survey. Clothing adjustment was affected largely by outdoor temperature and less by the immediate thermal environment. Number of occupants and time of occupancy decreased following the daily mean air temperature decrease in non-air-conditioned semi-outdoor environments. Occupants in semi-outdoor environments were tolerant of a two to three times wider range of environmental conditions compared to that predicted by PPD.