Daylighting assessment of window layouts and architectural elements in early design stages

Abstract

While window design evolves throughout the design process, establishing an initial concept is crucial. Architects often prioritize aesthetics when deciding on window layouts, yet considering daylighting performance early can significantly improve occupant health, well-being, and productivity. This study conducts a parametric analysis to assess the daylighting performance of different window layouts and architectural elements, including room layout, orientation, window to wall ratio, and visible transmittance (VT). Five window layouts were examined: square, rectangular, horizontal, vertical, and window wall. A total of 1,872 cases was simulated for Hanoi’s climate using Ladybug Tools. Results reveal substantial differences in daylighting performance among the layouts. Rectangular windows provide deeper illumination, while square windows distribute light more broadly near the window. Horizontal windows achieve greater daylight availability than vertical windows. Appropriately designed room dimensions and VT allow horizontal or vertical windows to maximize spatial daylight autonomy (sDA), while the window-wall configuration offers no substantial advantage. Window to wall ratio and VT are critical variables, capable of shifting sDA from 40 to 100%. Orientation also affects daylighting, with sDA differences of up to 15% between north- and west-facing windows. Based on these findings, early-stage window design guidelines are proposed to support effective daylighting performance.