Study of energy conservation between natural and mechanical ventilation in subtropical classroom

Energy consumption in subtropical classroom is different between natural ventilation and mechanical ventilation. Energy conservation is related with occupants´ thermal comfort in these two ventilation systems. This study proposed an electronic questionnaire and instruments to facilitate the continuous monitoring of the state of thermal comfort to investigate the satisfaction level of thermal comfort in the classroom. The investigated results show the clothing value (clo.) in 0.7 is the mean value. When the clo. is smaller than 0.7, the thermal comfort temperature range is between 22.0°C to 28.4°C in the natural ventilation and the range is between 24.8°C to 27.4°C in the mechanical ventilation (hot day). Besides, the thermal comfort temperature range is between 20.7°C to 23.3°C in the natural ventilation and the range is between 20.8°C to 25.4°C in the mechanical ventilation while the clo. is greater than 0.7 (cold day). The temperature range difference means the thermal comfort range of occupants in the hot day is widely and the temperature of natural ventilation is 1 °C higher than it in mechanical ventilation. The analysis of the the maxima thermal comfort temperature in natural ventilation in 28.4°C is higher than it in mechanical ventilation in 27.4°C and it is also higher than ASHREA standard 55 2004 in 26°C. It means the energy conservation in 6% (1°C) between natural ventilation and mechanical ventilation in the classroom of subtropical area and it also conserves 14.4% (2.4°C) with ASHREA standard 55. Based on this analysis, this study finds the best solution for energy conservation between natural and mechanical ventilation.