A review of reflected sunlight from buildings: problems and challenges

With the rapid development of urbanization and building technologies, reflective materials such as glass curtain walls and cool walls have been increasingly utilized, significantly impacting both indoor and outdoor lighting and thermal environments. This paper reviews studies related to the reflected sunlight from buildings on thermal performance and visual comfort, covering research methodologies and evaluation approaches. It compares the application of cool materials on roofs and façades; design strategies are proposed for urban planning and building design. The review reveals that numerical simulations have been widely employed in studies concerning outdoor reflected sunlight. However, there remains a lack of standardized evaluation criteria for outdoor lighting and thermal environments. The general conclusions regarding the impact of cool walls on building thermal loads and outdoor temperatures are still ambiguous, and systematic research on mitigating outdoor reflective radiation in urban planning and management is limited. Based on the review of existing studies, this paper proposes the challenges posed by reflected sunlight and provides theoretical foundations and practical guidance for building design and urban planning. This review paper is expected to contribute considerable significance for improving urban lighting environment and thermal comfort.