The layout of ceiling fans in buildings is challenging because of the need to co-ordinate with other elements in the ceiling space, and because the resulting airflows within the occupied space interact with furniture. This study conducted detailed air speed measurements in four buildings with different room sizes, furniture configurations, ceiling fan types, and ceiling-fan-to-floor-area ratios. We measured air speeds across the occupied spaces at four heights while varying ceiling fan operation modes such as fan rotational speed, operating direction, and the number of operating fans. In total, we collected 207,080 air speed samples at 343 sites under 20 test conditions. This paper presents the magnitude and distribution of air speeds, cooling effects, and their influencing factors. The Airspeed Coverage Index (ACI= (Fan air speed (SF)× Fan diameter (D))/√(Average area served per ceiling fan (A))) describes the combined effects of multiple influencing factors on the magnitude of air speed. ACI is employed to predict the average air speed and occupant cooling effect, yielding regression confidences higher than 0.95. When designing a space to a target airspeed or cooling effect, the ACI can help to determine parameters such as fan density required for fan choices. The measured data are compared with predictions from the CBE fan tool that had been developed from laboratory tests under simplified conditions. The comparison displays the blocking effects of the furniture, lowering the average air movement in the space, as well as reducing the air movement at the ankle level while increasing it at higher heights. The blocking effect increases with the density of the furniture. We also visually present fan interactions in which triplets of fans are arranged linearly or diagonally, showing that the diagonal layout of ceiling fans increases average air speed and improves its uniformity.

Many experimental studies demonstrated that elevating indoor temperatures to 28 or 30°C is comfortable if fans are used, while this elevation often is not applied in practice. This study aims to investigate AC thermostat use behaviors when elevated air movement is available, as well as to provide insights at guiding occupants to select warmer environments without reducing their comfort. 20 subjects participated in a series of tests at three initial ambient temperatures (26, 28, and 30°C) with different settings of an AC thermostat and a ceiling fan: (1) a free-controlled thermostat without a fan, (2) a free-controlled thermostat with a free-controlled fan, (3) a free-controlled thermostat with an always-on fan (controllable but not allowed to turn off), (4) a limited thermostat (no lower than 28°C) with a free-controlled fan, and (5) a limited thermostat with an always-on fan. The results show that without the ceiling fan, subjects used AC to lower indoor temperatures to 25.7°C. When the fan was available (free-controlled), they did not only rely on lowering the AC set-point alone but also turned on the fan immediately when starting using AC. This behavior ended a final ambient temperature up to 27.4°C. Under always-on fan conditions, the fan was running at a high speed at the beginning of using AC. Although subjects turned down the fan speed, the final fan speeds were about doubled the speeds as compared with free-controlled fan conditions. This higher initial speed by the always-on fan made subjects select higher indoor temperatures: at the 28°C initial temperature, there was no further lowering of ambient temperatures; at the 30°C initial temperature, the final temperatures were 28.6 and 28.9°C for the free-controlled and limited AC test conditions, about a 3-K set-points extension compared with the no-fan condition. Further, despite different conditions, more than 90% of subjects had comfortable feelings, which indicates that people with adjustable AC prefer a constant thermal perception rather than a constant ambient temperature. Therefore, the strategy of using fans before AC should be adopted to guide people actively to select higher AC set-point temperatures.