This book provides a comprehensive exploration of solar radiation modeling and its applications in building energy efficiency, offering readers practical tools to reduce energy consumption while maximizing renewable energy use. It introduces innovative models, including anisotropic diffuse radiation methods, haze-corrected frameworks, and photothermal integration approaches, supported by extensive data validation and advanced computational techniques. Special features such as clear illustrations, comparative analyses, and case-based evaluations bridge theory and engineering practice. The book also examines real-world challenges, from the effects of dust and rainfall on photovoltaic performance to the impact of air pollution on solar energy utilization. Readers will gain both theoretical understanding and practical strategies for optimizing solar applications in building design and renewable energy systems. It will appeal to graduate students, researchers, architects, engineers, and professionals engaged in solar energy and building performance optimization.