Building Energy Management Systems are implemented in buildings with mechanical, HVAC (heating, ventilation and air conditioning) and electrical systems to enable energy efficient control of the internal environment. The buildings themselves can vary widely in size and function. The purpose of a Controls Engineer is focused upon the control, performance and efficiency of energy usage and comfort control in industrial, commercial or public buildings of a diverse nature. It requires an associated understanding of these environments and the balance between cost, comfort, safety, health and wellbeing. It includes the specialist design, installation and commissioning expertise required to undertake this control and servicing function. Typically a BEMS Controls Engineer will be involved with designing the building energy management system that controls the building services (e.g. heating, air conditioning, renewables).They may also write related software and graphics as well as installing and commissioning such systems. Another key area is connecting and integrating with other building systems (e.g. security) to create 'Smart Buildings'. After the building is occupied and being used they may also be involved in servicing, maintenance and fault finding if there are problems with the system and energy performance reviews.