Shading as a Dual Thermal–Hygrometric Regulator in Saharan Residential Courtyards: Field Evidence and the Vegetation-Without-Shading Paradox in Laghouat, Algeria

Residential courtyards in Saharan cities face extreme summer thermal conditions that render them physiologically unusable for much of the day, yet their performance under standardized promotional-housing morphologies remains poorly documented. This study characterizes the summer environmental quality of a representative R+3 courtyard in Laghouat, Algeria (Köppen BWk), combining in situ measurements at five contrasting stations with ENVI-met simulation across six output maps. All five stations remained in the EXTREME physiological-stress category (PET = 51.1–52.3°C), with a peak thermal sur-plus of +4.87 to +5.97°C and minimum relative humidity of 9.26–10.35%. Sky view factor correlated strongly with thermal amplitude (r = 0.936) and shading with both humidity (r = 0.977) and comfort (PET, r = −0.887); given the small sample (n = 5), these associations are indicative rather than conclusive. A central finding is a vegetation paradox: the vege-tated, unshaded station recorded the highest thermal surplus and lowest humidity, con-sistent with stomatal closure under extreme aridity (VPD ≈7 kPa), while a shaded, vege-tated station performed best—indicating that shading, not vegetation per se, is the prima-ry regulator of courtyard microclimate here. ENVI-met simulation corroborates a 9.5°C surface-temperature differential between bare asphalt and shaded vegetated ground, in-forming bioclimatic redesign of Saharan promotional housing.