Abstract
To study the effects of cool airflow on sleep, human subject experiments were conducted on 10 healthy young men. The desired environmental conditions were attained by using (i) a normal air-conditioner fastened to the wall in one evaluation room and (ii) a new ceiling air-conditioner in another room. The new ceiling air-conditioner exhaust dispersed airflow from a 2-piece ceiling panel (1800×900mm) covered with a 3-dimensional knit fabric, such that the airflow from the air-conditioners was not directly perceived. The mean air temperature, relative humidity, mean radiant temperature, and air velocity in the evaluation rooms were 26.4℃, 58%, 26.3℃, and 0.14m/s, respectively, with the normal air-conditioner and 26.4℃, 53%, 26.1℃, and 0.04m/s, respectively, with the ceiling air-conditioner. The PMV (predicted mean vote) was -0.3 (0.7met, 1.15clo) in both the evaluation rooms. The maximum air velocity above the bed in the evaluation rooms and the frequency of airflow were 1.1m/s and 28 times per night, respectively, with the normal air-conditioner and 0.3m/s and 11 times per night, respectively, with the ceiling air-conditioner. The comfort sensation and the total duration of each sleep stage did not differ significantly with the normal and the ceiling air-conditioners. However, the subjects in the room with the normal air-conditioner felt a stronger draft and reported being a little colder. The skin temperature on the forehead, arm and hand that were not covered with the bedding clothes decreased due to cool airflow in the room with the normal air-conditioner. The number of waking, body movements, and the increase in heart rate were significantly lower with the ceiling air-conditioner than with the normal air-conditioner. The cool airflow produced by the normal air-conditioner was considered to disturb the sleep. Our results suggested that the new ceiling air-conditioner secured better sleep.
