Abstract
To determine the effectiveness of ceiling fans in enhancing comfort, 256 subjects were examined at 24.4 C (76 F), 26.1 C (79 F), 27.8 C (82 F), and 29.4 C (85 F) (all at 50% rh), in an environmental chamber that was equipped with a ceiling fan that produced four velocity conditions: 0.15 m/s (30 fpm), 0.25 m/s (50 fpm), 0.46 m/s (90 fpm), and 1.02 m/s (200 fpm). A fifth velocity, in which the fan was not employed, was 0.06 m/s (10 fpm); this served as the control velocity. Three subjective responses were measured: thermal sensation (a 9-category rating scale), thermal comfort (a 7-pair semantic differential scale), and a question on temperature preference. The results showed that an air plume from a ceiling fan whose velocity is between 0.5 and 1.0 m/s (90 and 200 fpm) compensates for a 2.8–3.3°C (5–6°F) temperature change; this represents an energy savings of 15–18% when based on the National Bureau of Standards' suggestion of a reduction in air conditioning energy demand of 6% per °C or 3% per °F. It also concluded that a ceiling fan may extend the upper limit of the summer comfort envelope from 26.1 to 29.4 C (79 to 85 F) and that the turbulent and variable characteristics of the air plume of the ceiling fan may be its major comfort-producing attribute.
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