School classrooms are obliged to set the aperture ratio to 1/5 or more of floor areas according to the Building Standards Law, and a large window opening is provided. In recent years, in the design of school facilities aimed at energy saving, window design is contrived to realize daylight use. However, providing a large area for daylight and taking in more sunlight is not directly related to the reduction of lighting energy. It is necessary to improve the uniformity of luminance and remove glare through architectural design such as a daylighting method and shading devices. Also, it is needed for users to turn off artificial lighting when the luminance is sufficiently obtained by daylight. Therefore, it is necessary to organize the problems of a school's daylighting and lighting plan, including the user's environmental adjustment behavior.
This study aims to indicate the environmental light conditions of classrooms with contrived windows, the actual use of artificial lighting and light shielding devices, and the problems and the possibilities of daylight use in school buildings. In two elementary schools where the daylighting method was contrived, we measured the light environment and surveyed its use. Additionally, we conducted a trial to reduce the use of artificial lighting with the cooperation of teachers and children.
From the measurement result of the light environment in the classroom, it was confirmed that the distribution in the classroom with multiple windows is more uniform, compared with the standard design type of school building with windows on the southern one side. Also, in the classroom with multiple windows, the recommended illuminance was satisfied at any measurement point on a sunny day, and the average luminance also fulfilled the design criteria. However, in winter, when the curtain was closed to avoid the incidence of direct light, the brightness ratio between the window surface and the inside of the classroom was large.
According to the survey of the use of the light shielding device and artificial lighting, it was indicated that the light shielding device is not only used for direct sunlight but, also, for shielding the eyesight. Artificial lighting is always used regardless of the brightness in the classroom.
From our results, we summarize factors to pay attention to reducing energy consumption by the use of daylight in school buildings. In window design, it is important to make the distribution of brightness uniform. Concerning light shielding devices such as curtains, it is necessary to examine light transmittance and reflection characteristics to shield daylight appropriately and to prevent glare and a high luminance ratio. Additionally, it is necessary to consider a switch system for artificial lighting that can turn off light on a brighter side and illuminate a darker side.
To reduce lighting energy in school buildings, environmental adjustment actions of the user also become necessary. In the trial to reduce the amount of artificial lighting, which collaborated with fifth-grade children, it was seen that the children understood the objective and importance, and adjusted the amount of artificial lighting and curtain use. As a result, it was indicated that energy savings from reduced artificial lighting could be realized if children were led to understand the proper light environment and the method needed to adjust the level of artificial lighting.
