Passive House is often associated with airtightness, insulation, and energy efficiency, but its true value lies in a deeper understanding of how buildings achieve comfort, durability, and exceptionally low energy demand. This book explores that understanding by connecting building science, architectural design, and construction practice into a coherent framework. Beginning with the fundamentals of energy use, climate response, and thermal comfort, the book explains how Passive House principles influence early design decisions such as form, orientation, glazing strategy, and enclosure design. It then examines the critical components of high-performance building envelopes, including insulation systems, airtightness, thermal bridge control, windows, and ventilation. The book goes beyond theory to explore real construction methods and assembly strategies, including: Masonry construction Timber frame systems Structural insulated panels (SIPs) Insulated concrete formwork (ICF) Hybrid construction approaches Detailed chapters explain how these systems can be used to achieve Passive House performance while maintaining buildability, durability, and architectural quality. Written for architects, builders, consultants, and advanced students, Understanding Passive House Design bridges the gap between performance theory and construction reality. Rather than presenting Passive House as a checklist of requirements, it shows how energy efficiency, comfort, and building quality emerge from clear design thinking and careful execution. Whether you are approaching Passive House for the first time or seeking a deeper technical understanding, this book provides a practical and thoughtful guide to designing and constructing high-performance buildings for the twenty-first century.