Energy savings for a junior high school classroom that actively uses daylighting and sensitivity study on the effect of the building envelope thermal performance

Abstract

This paper analyzes the energy-saving potential of lighting, including its effect on heating and cooling, and analyzes the effect of the thermal performance of a building on the annual energy consumption of a classroom actively using daylighting. The subject of this study is M Junior High School, located in Gifu, Japan. This school has a classroom design with a sloping roof, allowing the installation of large windows from north to south. The window-to-wall ratio of 56% for the south wall and 41% for the north wall takes advantage of daylight. Simulation results of illuminance in the classroom were validated through comparison with field measurement data. The result demonstrated that daylight utilization decreases lighting electric power consumption by 66.6% when artificial lighting is controlled in the classroom. The results confirmed that there was no significant heat load increase for heating and cooling even though the window surface area was larger than that of a typical classroom. The sensitivity study showed that the thermal performance of the building envelope mainly affects the heating energy consumption, but it has no significant effect on cooling and lighting energy consumption. In terms of the thermal performance of the building envelope and the amount of energy saving by daylight utilization, it is necessary to consider the appropriate thermal performance to determine cost-effectiveness.