Effect of thermal environmental control in summer on energy consumption and sleep

The reduction of energy consumption in the Japanese residential sector is a pressing issue because of climate change. However, an excessive reduction in air conditioner use to save energy could create a poor sleep environment. Therefore, the purpose of this research was to elucidate the impact of air conditioning on both energy consumption and sleep during the summer. Eight healthy male university students participated in this study, which was conducted in August 2013. Three thermal environmental control scenarios were used: natural draft, air conditioner set at 26.0 °C (continuous operation), and air conditioner set at 28.0 °C (continuous operation). Energy consumption, indoor thermal environment, and sleep state were measured during the experiment. The energy consumption for using an air conditioner for 8 h was reduced by 0.03 kWh/day/m² by increasing the temperature setting from 26.0 to 28.0 °C. Furthermore, the range of the average standard new effective temperature during sleep was from 27.6 to 31.4 °C (the average temperature during sleep was from 26.5 to 29.8 °C) where both energy saving and high-quality sleep were achieved. The results of this study indicate lifestyle changes are possible that allow both energy saving and high-quality sleep.