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Open Access Publications from the University of California

Global trends in thermal comfort in air conditioned and naturally ventilated offices in six climates


This paper compares occupants’ thermal response to naturally-ventilated and air-conditioned offices during the summer in four cool climate cities of developed economies (Midland in UK, San Francisco in US, and Melbourne and Brisbane in Australia) and four warm climate cities of developing economies (Bangkok in Thailand, and Bangalore, Jaipur and Chennai in India).  This analysis is some of the first done using data from both the ASHRAE Global Thermal Comfort Databases I and II.  Database II expands and is based on ASHRAE Database I (de Dear and Brager, 1998), led by teams at the Center for the Built Environment at University of California-Berkeley, University of Sydney, and Yongsei University Korea.  Results confirmed one of the fundamental tenants of adaptive theory, that the outdoor climate context mattered.  In the warm climate cities, occupants voted neutral at higher temperatures in both conditioning types, with a more distinct pattern for naturally ventilated buildings. Higher airspeeds and adaptive clothing are two contributing factors to this distinction. A comparison of thermal sensation and thermal preference allowed us to question what is considered ideal, and reveals that a majority of occupants preferred to be thermally neutral in summer.  Of the people preferring non-neutral sensations, more wanted a sensation of “slightly cool” compared to “slightly warm”.  This is an interesting observation relative to adaption, in that people are feeling more comfort at warmer temperatures, while at the same time preferring physical sensations on the cool side, which might be suggestive of the desire for sensory pleasures of alliesthesia.  Of the studies that asked questions directly about air movement preferences, occupants wanted more air movement beginning at the slightly cool thermal sensation even when airspeeds were above 0.2 m/s in elevated indoor air temperatures.

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