Assessing Urban Heat Island Dynamics in Hot-Arid Climates: Impacts of Building Materials, Morphology, and Urban Expansion

Urban Heat Island (UHI) formation is influenced by urban morphology, land use, vegetation cover, transportation, and construction materials. This study investigates the principal factors contributing to UHI formation in Shiraz, Iran, through a qualitative comparative assessment of five central districts, selected because they represent contrasting urban conditions within the same climatic context. The findings indicate that dense development, limited vegetation, extensive impervious surfaces, transportation-related heat emissions, and low-reflectivity façade and pavement materials are closely associated with accumulation of UHI. Accordingly, vegetation enhancement, sustainable transportation, cool roofs, and high-albedo materials were identified as relevant mitigation measures. Among these measures, improving construction materials was further assessed experimentally using polypropylene fiber-reinforced cementitious composites. Thermal transmittance and flexural-strength tests indicated stable thermal behavior and enhanced mechanical performance, with optimum results obtained at nano-clay contents of 3.0–4.5%. Although the experimental assessment does not directly quantify UHI reduction, it demonstrates the potential of sustainable cementitious materials to improve construction material performance and reduce cooling demand. The findings support the combined application of planning measures and experimentally assessed material solutions in hot semi-arid cities.