Building Automation Systems

The building automation system (BAS) has become the accepted technology used in controlling HVAC and other systems in most new commercial and institutional buildings (Figure 1). Existing buildings can be retrofitted with BASs, a change that has been shown to provide economically beneficial improvements in energy efficiency and occupant comfort. Although most BASs are designed primarily for HVAC control, many incorporate additional functions, such as lighting control, computerized maintenance scheduling, life-safety functions (such as smoke control), and access (security) control.

Figure 1: How building automation systems fit together
A building automation system (BAS) consists of sensors, controllers, actuators, and software. An operator interfaces with the system via a central workstation or web browser.

Building automation systems, which are present in more than half of all buildings in the U.S. larger than 100,000 square feet, save between 5 and 15 percent of overall building energy consumption. Generally, BASs are most cost-effective in buildings that consume lots of energy, such as data centers and hospitals. Older or poorly maintained buildings can also benefit greatly from a BAS retrofit, sometimes yielding savings of over 30 percent.

In addition to saving energy, BASs can reduce overall building maintenance costs by identifying operational problems early and often. For example, BASs can collect data from multiple zones around a building and display it on the system’s front-end computer. This enables the building operator to monitor and access the data to diagnose an operational problem rather than deploying a maintenance crew to search for it.

Unfortunately, many building automation systems save less energy than they could if set up optimally. In one detailed study of 11 buildings in New England with BASs, five of the buildings were found to be underachievers, producing less than 55 percent of expected savings. One site produced no savings at all.

To improve the likelihood that your BAS will achieve the expected benefits, you should take advantage of advanced control strategies that use the computer-processing power of a BAS and adopt a comprehensive approach to quality control known as commissioning. This process is now required for some buildings, such as public institutions and buildings certified by the U.S. Green Building Council’s LEED (Leadership in Energy and Environmental Design) program. Commissioning includes reviews and inspections throughout the design and construction process as well as rigorous performance tests that move the system through its sequences of operation before the building is occupied. Commissioning concludes when the building’s systems are working as planned and the operations team is thoroughly trained in using all of the system’s features.

It’s also important to ensure that a BAS continues to work properly over time. Recommissioning—in which building operators use trending and energy consumption data to periodically verify, document, and improve a building’s operation—can be conducted throughout the life of the building.

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