Radiant asymmetric thermal comfort evaluation for floor cooling system – A field study in office building

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Radiant cooling systems have the potential of reducing energy when compared with conventional air-conditioning systems. Thermal comfort evaluations for radiant cooling systems mainly focused on floor heating, chilled ceiling, and warm/cool wall, few have been known about the radiant floor cooling system. To validate the applicability of existing dissatisfaction models on radiant floor cooling systems, a field survey with continuous environmental measurements and subjective questionnaires was carried out in an office building in Shanghai. The results show that radiant asymmetries can affect occupants’ thermal comfort and acceptance rate significantly. The radiant floor cooling tends to cause more local discomfort complaints in the feet and calf parts than other radiant heating and cooling systems. The relationship (equation) between thermal dissatisfaction and asymmetrical radiations was developed, and the temperature thresholds s for the radiant floor cooling system were calculated. Based on these results, the short-term (2 h) and long-term (8 h) exposures at different levels of asymmetric radiation were compared and showed significant differences in occupants’ thermal satisfaction. The phenomenon of multi-directional asymmetric radiations (vertically and horizontally) was also observed and its effects were explored. Lastly, the design considerations, thermal comfort assessment, energy consumption, and operation strategy for the radiant floor cooling system were discussed.