Comfort, perceived air quality, and work performance in a low-power task-ambient conditioning system

Hui Zhang, Edward Arens, Dong Eun Kim, Elena Buchberger, Fred Bauman, Charlie Huizenga

Research output: Contribution to journalArticlepeer-review

242 Scopus citations


Zhang's thermal comfort model [Zhang H. Human thermal sensation and comfort in transient and non-uniform thermal environments, Ph.D. thesis, UC Berkeley; 2003. 415 pp.] predicts that the local comfort of feet, hands, and face predominates in determining a person's overall comfort in warm and cool conditions. We took advantage of this in designing a task-ambient conditioning (TAC) system that heats only the feet and hands, and cools only the hands and face, to provide comfort in a wide range of ambient environments. Per workstation, the TAC system uses less than 41 W for cooling and 59 W for heating. We tested the TAC system on 18 subjects in our environmental chamber, at temperatures representing a wide range of practical winter and summer conditions (18-30 °C). A total of 90 tests were done. We measured subjects' skin and core temperatures, obtained their subjective responses about thermal comfort, perceived air quality, and air movement preference. The subjects performed three different types of tasks to evaluate their productivity during the testing. The TAC system maintains good comfort levels across the entire temperature range tested. TAC did not significantly affect the task performance of the occupants compared to a neutral ambient condition. Whenever air motion was provided, perceived air quality was significantly improved, even if the air movement was re-circulated room air. In our tests, subjects found thermal environments acceptable even if they were judged slightly uncomfortable (-0.5). By reducing the amount of control normally needed in the overall building, the TAC system saves energy. Simulated annual heating and cooling energy savings with the TAC system are as much as 40%.

Original languageEnglish
Pages (from-to)29-39
Number of pages11
JournalBuilding and Environment
Issue number1
StatePublished - Jan 2010

Bibliographical note

Funding Information:
The authors are grateful to: UC Berkeley's Center for Information Technology Research in the Interest of Society (CITRIS) for support from its NSF ITR Grant # EIA-0122599, to the U.S. Environmental Protection Agency Award No: X-83232501-0, and to the Center for the Built Environment, UC Berkeley.


  • Comfort
  • Energy efficiency
  • Perceived air quality
  • Personal environmental control
  • Personal ventilation
  • Task-ambient conditioning


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