Indoor thermal conditions in the tropics are frequently too warm for thermal comfort, However, conventional air conditioning techniques involving vapor compression refrigeration are not universally used because both capital and energy costs tend to be high. Alternative systems such as evaporative or regenerative-evaporative coolers may be attractive on a cost basis but tend to have marginal performance in areas of high humidity. If the cooling system is absent or if its performance is marginal, people will elect to wear light clothing. They may also rely on the cooling effect of air movement, which aids the body's sensible heat loss and improves the evaporation, from the skin, of any perspiration. More experimental information is required on the amount by which the preferred temperature can be raised by air movement, particularly for people wearing light clothing. This report discus.ses an experimental technique designed to investigate the preferred velocity of a ceiling-mounted fan at various temperatures when the subjects are dressed in shorts and occupied in sedentary activity at a desk beneath the fan.

In normal comfort experiments, the subjects encounter a thermal condition that has been imposed by the experimenter, and they are asked to make judgements about the resulting thermal sensation. The technique adopted for these experiments was quite different, because the subjects were given an opportunity to choose a preferred condition by controlling the rotation rate of the ceiling fan. This approach may produ~e a different attitude in the subjects.