This problem book is a companion volume to the 2nd edition of the textbook "Building Physics: From Physical Principles to International Standards". The primary book offers a comprehensive presentation of the most important phenomena in building physics: heat transfer, moisture/humidity, sound/acoustics and illumination. The problem book includes both problems and solutions. Most of the problems are as practical as possible, while remaining conceptual and avoiding overreach. Many of the solutions presented do not simply end upon determination of the correct answer, but include further explanations for a deeper understanding of the theory and/or connections to other everyday phenomena. These explanations can be of great value to lecturers who use the primary book for their courses. All solutions are cross-referenced to the formulas or explanations in the primary book. This establishes the connection between theory and practice and contributes to a more thorough understanding of the subject. The book is primarily intended for lecturers and students of all subjects related to building physics.