A BMS is most common in a large building. Any organisation seeking to reduce its carbon emissions should first take a closer look at its BMS.

The principal role of a BMS is to regulate and monitor heating, ventilation and air conditioning. By operating fans or opening/closing dampers along with local controls a mixture of heating and cooling is used to achieve the desired room temperature. A secondary function sometimes is to monitor the level of human-generated CO2, mixing in outside air with waste air to increase the amount of oxygen while also minimising heat/cooling losses. Owners and tenants of non-domestic buildings are under mounting pressure to cut their energy usage and carbon emissions. They are faced by the prospect of higher utility prices and ever more stringent legislation, not to mention public and stakeholder demands that they show high standards of corporate social responsibility.

So what should be the first priority for hard-pressed energy and facilities managers? The logical answer is that they should focus on those areas where large energy savings can be made quickly and easily. This will often mean looking no further than their building energy management system.

A BMS can efficiently control as much as 84% of a building’s energy usage. By applying a range of control and monitoring routines – both simple and sophisticated – it is capable of operating the building services in strict accordance with demand, thereby avoiding unnecessary use of energy.

BMS systems are a critical component to managing energy demand. Improperly configured BMS systems are believed to account for 20% of building energy usage.

As well as controlling the building's internal environment, BMS systems are sometimes linked to access control (turnstiles and access doors controlling who is allowed access and egress to the building) or other security systems such as closed-circuit television (CCTV) and motion detectors. Fire alarm systems and elevators are also sometimes linked to a BMS, for example, if a fire is detected then the system could shut off dampers in the ventilation system to stop smoke spreading and send all the elevators to the ground floor and park them to prevent people from using them in the event of a fire.