Abstract
External shading regulates classroom daylight, yet the combined effects of panel projection depth, spacing, number and rotation angle remain poorly quantified for hot-humid-climate teaching buildings. Using a typical south-facing middle-school classroom in Guangzhou, China, this study summarized the simplest horizontal, vertical and comprehensive sunshade forms and ran 689 ECOTECT simulations under the CIE standard overcast sky, taking the average daylighting factor (DF) over the 800-mm-high working plane as the index. For all three forms the average DF correlates strongly and negatively with the total panel area (r = −0.878, −0.945 and −0.916; p < 0.01). The horizontal and comprehensive forms plateau at about 20 m² (DF ≈ 7.5%) and 25 m², while the vertical form does not; the strongest-shading form shifts from horizontal to comprehensive as the panel area grows from below 15 m² to 15–30 m². For horizontal combinations the average DF peaks at clockwise rotations of about 75° for a single panel and 45° (40°–50%) for multiple panels, and is lowest at about 45° counterclockwise; for vertical combinations it decreases almost linearly as the rotation magnitude increases from 15° to 75°. These findings support façade sunshade design for teaching buildings in southern China.