A STUDY OF NATURAL LIGHTING EFFICIENCY AS A SUSTAINABILITY INDICATOR

Abstract

This functional change significantly alters the building's spatial configuration, including façade orientation, opening positions, and interior spatial layout, which in turn directly affects the quality of daylighting within the building. This study aims to examine daylighting efficiency in type-36 houses converted to commercial use as a primary sustainability indicator. The methods employed combine field measurements using a lux meter at representative sampling points, daylighting simulation using Dialux Evo software, and comparative analysis against the SNI 03-6575-2001 illuminance standard — used as a minimum visual comfort reference despite being originally intended for artificial lighting — and GBCI as the sustainability target. Three sample converted buildings in a middle-class residential area in Pekanbaru City, with varying building orientations relative to the sun, were selected as research objects. Analysis showed that façade modifications, primarily the closure of original window openings and the addition of massive commercial signage, reduced the effective opening area to below 10% of the floor area. Simulation results showed interior illuminance levels ranging from 50–180 lux at peak daytime hours, far below the 250 lux standard (SNI baseline) and 300–500 lux (GBCI target) required for commercial spaces. Consequently, 72% of the converted buildings failed to meet the minimum SNI 03-6575-2001 illuminance standard, and none met the GBCI requirements (at least 30% of work area ≥300 lux or DF ≥2%), resulting in heavy dependence on artificial lighting and inefficient electricity consumption. Based on these findings, the study recommends daylighting retrofitting strategies tailored to spatial constraints, such as the application of light shelves, modular skylights, and transparent materials on vertical partitions to improve the daylight factor without compromising privacy and commercial function. These findings are expected to contribute to the development of design guidelines for residential-to-commercial adaptation oriented toward energy sustainability principles in tropical urban areas.