Exploring the visual–spatial correlation of daylighting and visibility in a university central library

Purpose University libraries function as complex learning environments where spatial configuration and environmental performance interact to shape the quality of interior study spaces. This study investigates the relationship between natural daylight availability and spatial visibility within the Main Library of the American University in Cairo. The research examines how climate-based daylight performance metrics relate to visibility-based spatial configuration measures, particularly within arid, high-illuminance environments. In doing so, it evaluates whether visually integrated areas of the spatial layout also correspond to favourable daylight conditions and visual comfort requirements within academic library interiors. Design/methodology/approach A mixed-methods analytical approach was adopted. Architectural drawings and digital models were first examined to establish the spatial structure of the library environment. Quantitative simulations were then conducted to evaluate daylight performance using climate-based metrics – spatial daylight autonomy (sDA), useful daylight illuminance (UDI) and annual sunlight exposure (ASE) – alongside dynamic visual comfort indicators, including daylight factor (DF) and daylight glare probability (DGP). These environmental metrics were analysed in relation to spatial configuration indicators derived from visibility graph analysis (VGA) within the space syntax framework, including visual integration, through-vision, visual control and isovist area. Statistical procedures, including ANOVA, correlation analysis and multiple regression modelling, were applied to examine the relationships between daylight performance and spatial configuration across the five levels of the library. Findings The results reveal a complex relationship between spatial visibility and daylight performance. Areas with high visual integration and centrality exhibited strong visibility indicators but generally lower daylight sufficiency, whereas perimeter zones near façade glazing achieved higher daylight autonomy while presenting a greater potential for glare and overexposure. Statistical analysis indicates contrasting associations between visibility-based spatial configuration measures and climate-based daylight metrics. These findings suggest a spatial–environmental trade-off between configurational centrality and daylight availability within the analysed library environment. Research limitations/implications The study is limited by its focus on a single case study located in an arid climate, which may constrain the generalisability of the findings to other climatic contexts and building types. In addition, the visibility analysis was conducted using spatial models derived from architectural plans, which may not fully represent the dynamic conditions of occupied environments. Although the statistical relationships identified are robust, causal interpretation remains limited due to other environmental variables not examined in this study, including acoustic conditions, thermal comfort and artificial lighting use. Nevertheless, the findings provide analytical insights that may inform the integration of daylighting considerations within spatially central areas of libraries and comparable public buildings. Practical implications The findings provide design guidance for architects and planners developing libraries and deep-plan public buildings in arid climates. Visually central spatial cores, while important for spatial connectivity, may require targeted daylight interventions such as clerestories, skylights, light wells and high-reflectance interior finishes to improve daylight sufficiency. Perimeter zones, although well daylit, require appropriate shading strategies to control glare and excessive solar exposure. Integrating visibility analysis with climate-based daylight metrics during early design stages can support more balanced spatial and environmental design decisions. Social implications By clarifying the relationship between spatial configuration and daylight availability, this study contributes to the design of more supportive learning environments within academic libraries. Aligning spatial visibility with adequate daylight conditions can improve visual comfort, spatial clarity and environmental quality in study spaces. In educational contexts – particularly in arid climates where daylight intensity is high – optimising daylight distribution while maintaining clear spatial organisation supports equitable access to comfortable and well-lit environments, reinforcing the role of libraries as inclusive and accessible places for study and academic engagement. Originality/value This research contributes an integrated analytical approach that combines climate-based daylight performance metrics with visibility-based spatial configuration analysis derived from space syntax. Unlike previous studies that examine daylighting or spatial configuration independently, the study demonstrates how visual centrality and daylight availability may diverge within deep-plan library environments. By linking environmental simulation with configurational analysis, the proposed framework provides a replicable method for evaluating the interaction between spatial structure and daylight performance in academic libraries and comparable public buildings.