Optimizing Energy Efficient Lighting Systems in Mosques Using Computational and Engineering Approaches

Javanese mosque architecture is distinguished by unique roof typologies that embody cultural heritage while shaping interior lighting quality. Preserving these architectural forms while addressing modern requirements for energy efficiency presents a key challenge. This study quantitatively analyzes the impact of traditional Javanese roof designs on daylighting performance, focusing on three prominent East Javanese mosques: the Great Mosque of Lamongan (three-tiered pyramid), the Great Mosque of Gresik (Meru layered roof), and the Great Mosque of Tuban (concrete dome). A mixed methodology was employed, combining computational modeling with field measurements. Illuminance data were collected using a lux meter to record indoor (Ei) and outdoor (Eo) values at different times of day. The Daylight Factor (DF), calculated as DF = (Ei/Eo) × 100%, served as the main indicator, benchmarked against the recommended 2–4% DF for public buildings and the 200-lux Indonesian National Standard. Findings reveal that roof typology strongly determines daylight penetration. The Lamongan Mosque, with its tiered pyramid roof, achieved the best performance, recording an average DF of 3.52% during Asr prayer time, falling within the recommended range. The Gresik Mosque demonstrated a DF of 1.99%, while the Tuban Mosque, with a modern concrete dome, achieved only 0.64%, indicating inadequate daylighting. This research concludes that traditional tiered roofs are more effective in providing natural illumination compared to modern domes, highlighting the value of integrating heritage design with sustainable engineering principles. The results contribute to strategies for adapting historic religious buildings to contemporary standards without compromising their cultural and aesthetic significance.