An HVAC system, or heating, ventilation, and air conditioning system, controls the temperature, humidity, and air quality of an indoor space. HVAC systems are used in homes, businesses, and industrial settings to create comfortable and safe environments.

System selection depends on three main factors including the building configuration, the climate conditions, and the owner desire. The design engineer is responsible for considering various systems and recommending more than one system to meet the goal and satisfy the owner of a building. Some criteria can be considered such as climate change (e.g., temperature, humidity, and space pressure), building capacity, spatial requirements, cost such as capital cost, operating cost, and maintenance cost, life cycle analysis, and reliability and flexibility.