Cooling systems are a fundamental technology to ensure adequate living conditions in the interior spaces of buildings. As climate change is increasing the outside temperature, cooling systems are experiencing greater use, which can affect the decarbonization objectives established for the built environment. Thus, aspects such as efficient technologies in cooling systems, user operating patterns, and user thermal expectations have a significant impact. In addition, the use of new refrigerants can have repercussions both on the operation of the installation and on the environment. This book is a compendium of research, studies, reviews, and case studies related to refrigeration system design and technology and energy efficiency and thermal comfort.