Orientation-Resolved Thermal and Hygric Performance of Camel-Hair-Reinforced Rammed-Earth Walls Versus Hollow Concrete Block: A Six-Month, Two-Climate Comparative Field Study

Field evidence for earthen and natural-fibre walls in hot climates remains scarce. This study reports a six-month field comparison of two wall constructions, instrumented on both faces at Riyadh (hot-arid) and Taif (milder highland), Saudi Arabia. Twenty-four sensors logged temperature and humidity every 15 min on three orientations of two open test cells with identical 300 mm walls: one of rammed earth reinforced with camel hair, the other of hollow concrete block. Twelve outer/inner wall pairs were analysed over 1708 wall-days. The earth wall damped the daily temperature swing more than the concrete block in every orientation at both sites: mean decrement factor 0.42 versus 0.58 at Taif and 0.47 versus 0.64 at Riyadh, holding on 86–99% of matched days. Mean inner-face amplitude fell from 12.5 to 7.0 °C at Riyadh. Time lag reached 3.2 h at Riyadh against 1.3 h for concrete block, but the materials were indistinguishable at Taif. Once construction moisture had dissipated, the earth wall damped the daily absolute-humidity swing by 57–58% against 11–48% for concrete block. Because the cells are open and unconditioned, these descriptors are comparative indices rather than transferable wall properties, and no cooling-load saving is inferred.