Overcast skies are defined by diffuse illumination and low luminance contrast, often producing visually flat and uninspiring interior environments in northern climates. This study investigates whether small, low-cost optical components can be retrofitted onto existing windows to enhance the perceptual quality of daylight in north-facing rooms of multi-story buildings. The research examines how reflective, refractive, and diffractive elements—concave mirrors, plano-convex lenses, Fresnel lenses, and hologram sheets—modify diffused daylight to introduce spatial contrast or color under overcast sky conditions.A 1:8 physical model was used to test thirty-eight iterations using these devices, with each configuration assessed under real overcast daylight. Eighteen iterations demonstrating the strongest effects were selected for detailed analysis. Results indicate that concave mirrors clearly outperform lenses in concentrating diffuse light: they produced sharper light patches, cast defined shadows, and generated contrast. Transparent hologram sheets created strong color dispersion but often oversaturated the interior due to transmitted refracted light. Opaque-backed hologram sheets successfully mitigated this issue by eliminating transmission while preserving desirable reflective and diffractive qualities. Together, these findings reveal two distinct pathways for qualitative daylight enhancement in overcast climates: contrast-based strategies using direct reflections, and color-based strategies using controlled diffraction.Building on these insights, the study proposes nine retrofit design solutions that integrate optical elements as adjustable, user-controlled components within existing window assemblies. These add-on systems offer a practical, non-invasive, and cost-effective approach to improving visual interest, occupant experience, and perceived daylight quality in buildings located in predominantly overcast regions.

This study evaluates the annual daylight performance of solid and perforated exterior shading devices across two contrasting climates, San Antonio, TX, and Seattle, WA. Using a standardized 10 × 10 × 10 ft testbed and a parametric simulation workflow in Climate Studio, the analysis compares vertical fins and overhang-based strategies with perforation ratios of 20%, 40%, and 60% across south, east, and west orientations. Daylight performance is assessed using LEED v4.1 climate-based daylight metrics, Spatial Daylight Autonomy (sDA300/50) and Annual Sunlight Exposure (ASE1000/250).

Results indicate that shading performance is strongly climate and orientation dependent, and perforation does not universally outperform solid shading. In San Antonio’s sun dominant conditions, solid shading and low perforation (approximately 20%) provide the most reliable ASE control while maintaining daylight availability, whereas high perforation (60%) increases overexposure and is not recommended. On east façades in San Antonio, ASE reductions are largely insensitive to perforation level, while west façades remain most sensitive to low angle afternoon sun, favoring solid fins or low perforation for limiting ASE. In Seattle’s diffuse dominant context, low perforation (approximately 20%) most consistently matches solid shading in ASE control while preserving high sDA, whereas higher perforation ratios (40–60%) are more façade dependent and can reduce the ASE benefits achieved by solid or low perforation devices, particularly on the south and east façades. Overall, the findings position perforated shading as a climate responsive alternative to solid shading that can preserve daylight access while controlling overexposure when perforation ratio and orientation are selected in alignment with local sky conditions.

In terms of Indoor Environmental Quality (IEQ), providing sufficient daylight and access to outdoor views is important for occupants’ health and productivity. Consequently, contemporary architectural design increasingly adopts high Window-to-Wall Ratios (WWR) to maximize daylight penetration and visual connectivity. However, high WWR, particularly in office perimeter zones, often results in excessive direct solar penetration and severe glare conditions. Conventional static shading systems exhibit limited capacity to consistently balance daylight admission and glare mitigation under dynamically changing solar conditions. Although dynamic shading systems allow more responsive control strategies, single-axis systems remain insufficient in addressing the simultaneous variations of solar azimuth and altitude angles, while multi-axis kinetic facades often encounter practical limitations due to mechanical complexity and implementation constraints. Within this context, a dual-axis dynamic shading system capable of independently responding to both solar azimuth and altitude angles is proposed as a practical solution to simultaneously enhance daylight regulation and glare control. This study evaluates the proposed dual-axis dynamic system on a room-scale south-facing facade located in Phoenix, Arizona, where high solar radiation and exterior illuminance levels necessitate carefully optimized shading strategies. To comprehensively assess visual environmental performance, an integrated metric Mutual Satisfied Area (MSA) was introduced, combining useful daylight, glare probability, and unobstructed view ratio into a unified performance index. The results indicate that, compared to a conventional static horizontal louver system, both grid-based array scenarios (7×7 and 14×14) achieved higher MSA values. Furthermore, correlation analysis revealed that the most influential design parameters affecting MSA were the shading panel width and height, which determine the inter-panel spacing within the grid configuration, whereas the distance between the facade and the shading system exhibited relatively minor impact on overall performance.