Assessing the Role of Sunlight Exposure in Lighting Performance and Lighting Energy Performance in Learning Environments: A Case Study in South Korea

In South Korea, sunlight rights and daylight rights are legally distinguished, yet no standardized methodology exists for their quantitative assessment. Current evaluations of sunlight rights are narrowly defined, relying on the duration of direct solar penetration at the window center during the winter solstice, while excluding reflected and diffuse light. This restrictive approach has led to confusion among both researchers and legal practitioners, as it diverges from daylighting evaluations that account for indoor brightness and energy performance. The recent enactment of regulations to secure solar access in schools has further intensified disputes between educational institutions striving to protect students’ visual comfort and developers seeking to maximize building potential. To address this gap, this study proposes an evaluation framework tailored to the Korean context. A reference classroom model representative of standard Korean schools was developed, and simulations were conducted by introducing obstructing building masses to block direct sunlight. The methodology evaluated key variables, including time of day and solar altitude, and analyzed daylighting performance and lighting-related energy consumption under obstructed conditions. The results show that blocking sunlight through south-facing windows reduces daylighting performance by 89% to 98%, leading to additional reliance on artificial lighting, with energy use increasing between 128 Wh and 768 Wh. These findings underscore the limitations of current legal interpretations based solely on sunlight duration and highlight the necessity of adopting performance-based evaluation methods. Protecting school sunlight rights through such approaches is essential to enhancing classroom visual environments and reducing energy demand.