Save. HVAC is an abbreviation for Heating, Ventilation and Air Conditioning. HVAC systems are the main mechanical infrastructure of a building and provide climate control functions. An HVAC system can range from a compact unit placed in a window sill to a multisystem unit that is installed on a roof or in a basement.HVAC systems are typically the most costly elements of construction.eatures. An HVAC system has the ability to pump hot, cold or fresh air into an area. It pulls fresh air from the outside and then alters it to the desired temperature. Often HVAC systems use hot or cold water to either chill or heat the air.