Analysis and evaluation of the effect of reflectance values on internal walls, internal roofs, and light shelf on optimal illumination levels in the diploma economics and business building of the vocational school UGM, Yogyakarta

The use of natural light as a source of lighting in buildings is an option in energy saving. One of the efforts that has been made is the installation of a light shelf. The light shelf installed in the UGM Vocational School Economics and Business Diploma (DEB SV) building is not fully working optimally. As many as 83% of the light shelf in lecture rooms is covered by curtains because it is considered to produce excess light (glare). This results in a greater consumption of lighting electricity. This study was conducted to analyze and evaluate the effect of the reflectance value (color) attached to the internal walls, internal roof, external light shelf, and internal light shelf on the indicator of illumination levels Useful Daylight Illuminance (UDI). Furthermore, this study aims to determine the optimum reflectance value (color) parameter. The research was conducted with a simulation method using RadianceIES in the IESVE 2021 software. The first simulation results show the value of reflectance (color) installed (base case) on the internal wall, internal roof, external light shelf, and internal light shelf in one of the lecture rooms of the DEB SV UGM building resulting in a very large value of the UDI_>2000lux indicator, which is 84,9% (not according to the criteria). The results of the second simulation provide two variations of the optimum reflectance (color) parameters in the independent variable. The first variation is the internal walls, internal roof, external light shelf, and internal light shelf, each of which has a reflectance value (color) of 90,67% (beige), 100% (white), 90,67% (beige), and 100% (white). The second variation is the internal walls, internal roof, exte rnal light shelf, and internal light shelf, each of which has a reflectance value (color) of 90,67% (beige), 100% (white), 90,67% (beige), and 90,67% (beige).