Cool wall claddings for a sustainable future: A comprehensive review on mitigating urban heat island effects and reducing carbon emissions in the built environment

The building sector is a major contributor to global greenhouse gas emissions, accounting for approximately 40% of total energy-related CO2 emissions. The growing urban heat island (UHI) effect and the rising energy demand for cooling have intensified the need for innovative building materials that enhance thermal efficiency while minimizing environmental impact. Despite advancements in cool wall cladding materials, knowledge gaps remain regarding their long-term performance, scalability, and the trade-offs between embodied carbon and operational energy savings. This study addresses these gaps by conducting a comprehensive review of recent developments in cool wall technologies, with a focus on advanced solutions such as radiative cooling coatings, retroreflective surfaces, and high-emissivity paints. A systematic review of approximately thousand peerreviewed journal articles and conference papers, published within the last decade and sourced from Google Scholar and Scopus, was conducted to evaluate these advancements. Studies were selected based on their relevance to urban heat mitigation, energy efficiency, and life cycle assessment of building envelopes. The review examines both numerical modeling techniques (e.g., Finite Element Method (FEM), Finite Volume Method (FVM), and Computational Fluid Dynamics (CFD) simulations) and experimental validations to assess the effectiveness of cool wall materials. The findings indicate that while these technologies effectively reduce surface and ambient temperatures, their net carbon reduction potential is influenced by material selection, insulation properties, and regional climatic conditions. Notably, under optimal conditions, cool cladding materials can achieve net carbon reductions through operational energy savings, despite variations in embodied carbon impacts. However, challenges such as long-term durability, scalability, and potential heating penalties in colder climates highlight the need for further research into adaptive emissivity technologies and cost-effective manufacturing methods. Addressing these challenges will enable cool wall cladding materials to play a transformative role in developing energy-efficient and climate-resilient buildings.