Air conditioning refers to the cooling and dehumidification of indoor air for thermal comfort. This requires systems for heating, venting and air conditioning (HVAC). This book discusses the application and performance on thermal comfort, indoor air quality and energy efficiency of a variety of room air distribution modes. Efficient energy performance of HVAC systems due to active and passive control of energy consumption are also addressed. Furthermore, this book explores a passive energy system, called air-conditioning cupboard which exploit renewable energies as thermal sources for the purpose of saving energy. Additionally, the thermal supply for air conditioning systems can be carried out efficiently using reversible air pumps. Thus this book examines how to improve the design of these pumps, which have great potential, particularly in Mediterranean climates. Other chapters in this book explore the use of artificial neural networks (ANN) for air conditioning systems; the ventilation concepts utilising ambient energy from air ground and other renewable energy sources and different types of air-conditioning systems with good energy-saving potential, such as the liquid desiccant cooling system (LDCS) and solar-powered air-conditioning systems.