Experiment and MaterialsIn this experiment, the room was the bedroom of 20 square meters with single phase split type airconditioner (18000 BTU), ultrasonic humidifier (200 millilitres per hour), electric heater (2 kilowatts)and inverter to control the speed of compressor (Figure 3). The temperature and relative humidity aredetected by STH15. The data were recorded by Hioki datalogger at every 5 second for 8 hours from 10pm to 6 am. The experiment was divided into 2 cases: Case 1 (Figure 3) used inverter to control thespeed of compressor motor of air-conditioner and it had ultrasonic humidifier along with electricheater to control both temperature and relative humidity. The temperature and relative humidity wereset at 28.5 degrees Celsius and 50-60% respectively. Case 2 (Figure 4) used thermostat to controlcompressor of the air-conditioner without relative humidity control system. The temperature was set at26 degrees Celsius. The data concerning temperature and relative humidity in the room was recordedas done in Case 1. During the experiment, the data concerning temperature and relative humidityoutside the room was also recorded from 6 am every 2 minutes for 24 hours. There were 703 records(Figure 5). After considering temperature and relative humidity in Figure 5, we found that during nighttime relative humidity reached 80% whereas during day time relative humidity was about 45% whichwas quite low. This indicated that Thailand has high relative humidity.