Effects of natural light on improving the lighting and energy efficiency of buildings: toward low energy consumption and CO2 emission

Visual information acquisition is essential for our daily lives, with vision relying on the presence of light. Lighting systems serve the fundamental purpose of enabling vision. This study aims to contribute to sustainable architectural design by emphasizing the efficient utilization of natural daylight. Specifically, the design of skylights or light wells in low–lateral-area, deep-depth structures is of significant importance. While current design criteria consider skylight dimensions and the skylight-to-building height ratio, these factors alone may not suffice for optimal skylight design. To achieve an appropriate lighting and architectural design for such structures, it is essential to evaluate the factors influencing the required amount of daylight on different floors. This study aims to investigate the impact of skylights and light wells on the energy consumption and CO2 emissions of a four-storey building located in Hail, Kingdom of Saudi Arabia. The physical parameters of skylights and light wells were analyzed, taking into account various aspects that affect the amount of light reaching different levels. The findings highlight the significant influence of skylight size on the light reaching the building’s floors. For square skylights, reducing the well index (increasing skylight size) exponentially increases the daylight factor. Furthermore, this study evaluates the annual energy consumption and carbon dioxide emissions of the building, considering the daylighting factor. The results demonstrate that skylights contribute to increased solar heat gain, thermal conductance, and artificial lighting efficiency. Notably, as the lighting factor of the building increases from 3% to 6%, there is an annual decrease of 3% in CO2 emissions.