A building management system (BMS) is the computer-based control system that monitors and operates a building's mechanical and electrical equipment: heating, ventilation and air conditioning (HVAC), lighting, power, fire and life-safety systems, elevators, and access control. It is also called a building automation system (BAS) or building energy management system (BEMS).
What a BMS does
Sensors and controllers on each piece of equipment report to a central server and operator interface. The BMS schedules equipment, holds set points, raises alarms when a value drifts out of range, logs energy use and trends, and lets facilities staff adjust the building from one screen. Larger systems talk to equipment over open protocols such as BACnet, Modbus and LonWorks, so controls from different manufacturers can be combined.
BMS versus BAS
The two terms are used interchangeably in most of the industry. Where a distinction is drawn, "building automation system" refers to the controls layer that runs HVAC and lighting, and "building management system" to the wider supervisory layer that also covers security, fire, metering and reporting.
Why it matters on a construction project
The BMS is usually a separate controls package under the mechanical or electrical contract, with its own submittals, commissioning and points list. Because it touches every trade, controls work is a common source of change orders and back-charges late in a project. Tracking the controls subcontract, its material purchases and its field expenses against their own cost codes keeps those costs visible before closeout.
Related terms
Building automation system (BAS), direct digital control (DDC), commissioning, HVAC, energy management.
