Integrated spherical phase change modules in concrete roofs enhance thermal performance in hot climates

Rising energy demand for building cooling exacerbates the environmental challenges associated with energy consumption. Incorporating phase change materials (PCMs) into building envelopes, particularly sun‑exposed roofs, can substantially reduce energy use. This study examines the thermal‑storage efficiency of metallic, spherical PCM modules embedded within a reinforced concrete roof, designed for hot‑climate conditions. The roof is divided into four distinct thermal zones: Zone‑1 (conventional concrete), Zone‑2 (empty spherical modules), and Zones 3-4 (modules filled with organic PCMs, organic mixture, 35 °C (OM35) and organic mixture, 37 °C (OM37)). Important thermal performance metrics, such as temperature distribution, heat flux, thermal load, time lag, decrement factor, key response index, and carbon emissions savings, are evaluated. Integrating spherical PCM modules led to significant improvements. These include an average reduction in indoor surface temperature of 10.2 °C, a decrease in cooling load of upto 69%, and a reduced decrement factor. In addition, OM35 showed a higher key response index and enhanced thermal performance than OM37. The findings demonstrate the practical viability of spherical PCM‑integrated roofs as a passive‑cooling strategy for buildings in hot climates.