Building Automation System (BAS) is a term applied to the HVAC controls for a facility that maintain comfortable conditions in the occupied spaces. This is accomplished by controlling all elements in the mechanical systems from central plant equipment to individual zone valves and dampers. All levels of control communicate with each other and to a central BAS controller that coordinates all control activity. Controllers can either be pre-programmed or custom programmed to meet the unique needs of the facility. Custom programming gives the flexibility to minimize energy consumption while giving optimum environmental comfort conditions and allows adaption to modified requirements caused by usage changes.

The BAS gives the facility manager insight into the operation of facility's environmental controls and advanced warning of potential problems or notice of equipment failure. Either through a graphical interface or tabular data, the facility manager can maintain real-time control of the facility, schedule occupancy and monitor all critical aspects of the mechanical systems. Alarms can be e-mailed to service personnel so that equipment failure can be reacted to before building conditions deteriorate to the level of generating complaints. Load shedding and other cost avoidance measures can be implemented to minimize energy consumption costs. Tenant buildings, security, and lighting control can be incorporated into the BMS to centralize all these functions at a single location. Multiple levels of access can be provided to ensure that all involved personnel have only the information and the control necessary to perform their function.

Building Automation Systems are expandable to meet incorporation of additional space within an existing facility or new construction. Since the control intelligence is contained withing the local controllers, loss of network communications does not adversely affect building operations.