In the beginning, the goal is to enable the operations and maintenance staff to work with the system to give it the best chance to perform as designed. Later, the vision is a culture of continuous improvement that can withstand changes in technology and personnel. In between? Plenty of opportunity for thoughtful operations and standardized routines.
We almost always think about the BAS as a tool that is a critical part of energy management, so these systems are typically focused on those systems that directly use energy — notably the HVAC and lighting systems.
Generally, when we think about BAS, it is in the context of large commercial buildings, those well over 25,000 sq ft. According to the latest government data though (from the 2012 Commercial Building Energy Consumption Survey), 88% of all commercial buildings are 25,000 sq ft or less.