2018 Volume 43 Issue 253 Pages 9-21
The use of natural ventilation to improve the comfort of a room is considered difficult because the indoor ventilation performance will decrease on increasing the floor space. In this study, we evaluated the performance of a natural ventilation system in a large-floor-space office by calculating the inflow and outflow of air through a ventilation window based on differential pressure measurement. To evaluate performance, we analyzed the relation between outside wind at the time of natural ventilation and air inflow and outflow through a ventilation window. The results show that the eastern and northern faces have greater inflows, and an outside wind direction that is more toward the windward side with respect to each surface tended to yield a greater air inflow. In addition, we calculated the air change per hour in a residential area by the carbon-dioxide method. It was clarified from the CO2 concentration that the ventilation performance is different for each measurement point. As natural ventilation resulted in a warm indoor temperature environment, we analyzed the relation among the temperature different between the inside and outside, air inflow and outflow, and the indoor temperature environment. The results show that the temperature difference between the inside and outside became small with natural ventilation, and the difference tended to fluctuate with a change of air inflow and outflow. In addition, the indoor temperature was within ± 2 degrees Celsius from the air-conditioning temperature setting of 26 degrees Celsius. We evaluated the thermal sensation of people in the office at the time of operation of the natural ventilation system by a questionnaire survey.
