Aims
Daylight plays a critical role in shaping both the visual performance and melanopic effects of indoor environments, influencing circadian rhythms, alertness, and overall well-being. In office environments, where occupants typically spend a substantial portion of their daytime indoors, the quality and quantity of daylight are particularly important. Despite its importance, the effectiveness of daylight in interior spaces is often constrained by spatial geometry and orientation, which affect daylight penetration, distribution, and biological impact. However, daylight performance is not determined solely by window characteristics or façade design. The spatial configuration of an interior space, including its depth, width, and overall proportions, directly influences the penetration and spatial distribution of daylight. Building orientation further modifies these conditions by determining the amount, direction, and temporal pattern of solar radiation entering the space. Despite the growing interest in considering both visual and non-visual aspects of daylight, the combined influence of spatial proportions and cardinal orientation on visual performance and melanopic effects has received comparatively limited attention. This study aims to investigate the influence of spatial proportions and cardinal orientation on visual performance and melanopic effects of daylight in office spaces in Tehran, with particular emphasis on the relationship between room geometry and the balance between visual daylight performance and melanopic exposure.

Research Method
A total of 81 test rooms with different spatial dimensions and proportions were modeled under four cardinal orientations. The test rooms were developed to represent variations in spatial configuration while maintaining comparable boundary conditions for systematic comparison. The daylight performance of the test rooms was evaluated using both visual performance and melanopic effects indicators. Equivalent Melanopic Lux (EML) was used to assess the melanopic effects of daylight, while Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE) were used to evaluate visual performance of daylight. Melanopic effects of daylight conditions were simulated using the ALFA plugin, while visual performance of daylight was analyzed using Ladybug Tools. The results were examined comparatively across the different spatial proportions and orientations to determine the extent to which room geometry and orientation affect the magnitude, distribution, and temporal characteristics of daylight. Particular attention was given to the relationships and potential trade-offs among EML, sDA, and ASE rather than evaluating each indicator independently.

Results and Discussion
The results indicate that the depth-to-width ratio is a determining factor in the daylight behavior of office spaces and can simultaneously affect EML, sDA, and ASE. Changes in spatial proportions affect the penetration and distribution of daylight within the room, thereby modifying both the availability of daylight and its melanopic component. The effect of room geometry, however, varies according to cardinal orientation, demonstrating that spatial proportions cannot be interpreted independently of the direction of the façade. Among the four orientations, the southern orientation showed the highest daylight availability and EML values due to greater solar exposure; however, increased direct solar radiation near the window was associated with higher ASE and a greater potential for visual performance issues. In the northern orientation, lower sDA and EML values were observed, while daylight distribution was more uniform and direct solar exposure was lower. The eastern and western orientations exhibited greater temporal variation in daylight performance, reflecting differences in the timing of solar exposure throughout the day. These findings highlight that a spatial configuration that increases daylight availability does not necessarily produce the same response across all orientations or across visual and melanopic indicators.

Conclusion
The findings demonstrate that spatial proportions cannot be evaluated independently of building orientation when assessing integrated visual performance and melanopic effects of daylight. Appropriate selection of room depth, width, and their ratio, together with consideration of cardinal orientation, can contribute to achieving a more balanced daylight environment in office spaces. Consequently, room depth, width, and their ratio should not be considered independently from cardinal orientation when visual performance and melanopic effects of daylight are evaluated simultaneously. Appropriate selection of spatial proportions, together with orientation-sensitive design decisions, can contribute to achieving a more balanced daylight environment by considering both daylight availability and melanopic exposure while limiting excessive direct solar exposure. The results provide a basis for considering spatial geometry as an important design parameter in the early stages of architectural design, particularly when visual performance and melanopic effects of daylight are considered simultaneously. The study emphasizes the importance of incorporating spatial geometry into daylight design at the early stages of architectural design, rather than treating daylight performance solely as a consequence of window or façade configuration. By considering visual and melanopic dimensions together, the findings provide a basis for a more integrated interpretation of daylight performance in office environments in Tehran and support the consideration of room proportions and orientation as complementary design parameters in early architectural decision-making.