Smaller commercial buildings represent a significant portion of the country’s building inventory, measured by aggregate square footage as well as by building count. Buildings smaller than 100,000 square feet in size represent 98% of all commercial buildings and 35% of building floor space in the United States. These buildings also represent a meaningful percentage of all of the energy currently consumed by commercial buildings. This is a large, attractive energy consumption target to address using measures to improve energy efficiency.
Other considerations suggest that these buildings are a good place to implement energy efficiency improvements. Smaller commercial buildings are as energy intensive as their larger counterparts. Yet many of these buildings, both new and old, have not received the investment in energy efficiency improvements that have been directed at larger buildings that are more visibly expensive to operate. In addition, smaller buildings tend to receive less service, equipment maintenance, repair and facility upgrades than larger buildings. Finally, many of these buildings do not have building automation systems and rely on controls with rudimentary functions offering only a modest improvement in energy consumption.
Building Automation Systems (BAS) can make meaningful reductions in the energy consumed by smaller commercial buildings. By taking over operation of a building’s lighting and HVAC systems, as well as other aspects of building operations, a BAS can deliver usability, comfort and environmental quality for smaller buildings - something that these systems have been providing to larger buildings for decades. Building automation systems deliver comfort while also reducing the building’s energy consumption.
Challenge of Traditional Building Automation Systems
Benefits aside, there are distinct challenges to installing building automation systems in smaller buildings. While a BAS is necessary to run the complex HVAC systems of larger buildings, the systems in smaller buildings can be operated with low end thermostatic controls. In addition, traditional BAS systems have been relatively expensive for smaller buildings, both in equipment and installation costs The end result is often a weak ROI for small building BAS. Some of the more common challenges include:
• Types of HVAC Systems:
Small buildings differ from large buildings in several characteristics that may require a different type of BAS. First and foremost, HVAC systems differ markedly between large and small buildings. Large buildings use central plant HVAC systems based on large centralized equipment – chillers and boilers – that generate cold and hot water. This water is then piped around the building to heat exchangers in air handling units or fan coil units, and then the cooled or heated air is delivered to each zone of occupied space. Smaller buildings, on the other hand, can not afford the cost and space requirements of central plant systems with water distribution plumbing. They use some form of packaged HVAC system to directly cool or heat the air that a fan then blows into occupied space. In smaller buildings, there is often one packaged unit per zone. A large building BAS that is designed to manage a central plant, a water distribution system, and independent units for heating and cooling air. It is not designed to manage efficiently a large number of independent packaged units that deliver conditioned air directly to occupied space.
• Complex Controller Architecture:
Traditional building automation systems are inappropriate for smaller buildings in other ways. Traditional systems are structured around several layers of controllers, with unit controllers managing individual equipment, which may in turn be managed by a zone controller, with the overall building managed by a separate supervisory controller. A building automation workstation then provides the interface between the supervisory controller and the facility management staff. While this structure may be necessary to manage the large number of devices and multiple zones of large buildings, it is an unnecessarily expensive infrastructure for managing smaller buildings. In addition, traditional building automation systems are increasingly oriented toward directly interfacing to intelligent equipment using sophisticated building automation communications protocols, such as BACnet or LONtalk. In smaller buildings, on the other hand, the HVAC and other equipment seldom includes the additional expense of supporting these protocols, and they are instead controlled by simple digital on-off signals.
• Retrofitting:
Most smaller buildings are not currently equipped with sophisticated building automation systems, and the opportunity to reduce energy consumption in these buildings is to retrofit a BAS into these buildings. Traditional BAS are intended to be engineered into the building during its design and installed during the extended building construction process. Moreover, each large building is fairly unique, and the BAS is custom engineering to serve each building. Serving smaller buildings, which require a low cost solution that can be retrofitted easily, is not a good fit with the characteristics of traditional building automation systems.
Smaller Buildings Require A Different BAS
Smaller buildings require a targeted building automation system that is different from that traditionally employed in larger buildings. Smaller buildings are less complex, with the lower equipment count and lower energy bills that implies. Smaller buildings also lack on-site maintenance and facility management staff to monitor and operate a BAS. The equipment in smaller buildings is usually less well maintained and only gets attention when it breaks. A building automation system needs to account for these characteristics of smaller buildings.
A building automation system for smaller buildings must be “smaller” and less expensive than traditional systems. It must be cost effective at the smaller scale, with low infrastructure overhead while still able to control and reduce the energy consumption of the building’s equipment. It can not require multiple levels of supervisory controllers or dedicated operator workstations. This BAS must be relatively inexpensive to install as a retrofit, using wireless or other approaches to reduce wiring costs.
The building automation system must also control the type of equipment normally found in a smaller building, and do in a way that saves significant energy. Particularly for the HVAC subsystem, the BAS needs to control a large number of zone-dedicated packaged systems, and do so in a way that reflects zone occupancy and the operation of systems in the adjacent zones. To minimize energy consumption of this HVAC configuration, the operation of all zones must be coordinated to achieve the overall building requirements for comfort. The BAS needs to control with a high level of functionality without expecting intelligent unit controllers to already be installed in the building’s equipment.
The overall architecture of a BAS for smaller buildings must be built around the premise of remote operation and management. Smaller buildings are managed by a central staff, and the BAS must communicate well with a central system. Changes to setpoints and schedules must be easy to perform from a central monitoring location, and identical changes to multiple buildings should be similarly easy. Building operating data needs to be archived centrally for remote analysis and diagnostics. Similarly, alerting and alarming should be communicated to a central point for consolidated analysis and processing. The smaller building BAS does not just need to communicate with a central site, but it needs to communicate a significant amount of information to enable the building to be effectively managed remotely.
Because proper maintenance of equipment is important to its energy efficient operation, and because smaller buildings are not often maintained regularly, a BAS for smaller buildings needs to support predictive or condition-based maintenance. The BAS needs to automatically determine which equipment is beginning to underperform, and to help the central monitoring staff understand which deterioration is having the greatest impact on energy efficiency.
A building automation system retrofit into a smaller building must generate more than enough energy savings to justify the cost of installing the system. To accomplish this in a small format building, the BAS must control all of the building and its equipment in an integrated, coordinated approach that covers lighting HVAC and other significant energy consuming devices in the building. The BAS must help maintain efficient equipment performance through tight control, continuous monitoring, exception reporting and on-going commissioning. The BAS may also need to take over unit control functions for equipment whose integral controllers are inefficient or can not be managed to operate in concert with the rest of the building. Generating energy cost savings will also require the BAS to support peak demand leveling, demand response support, and controlling based on time-of-day pricing as these become more universally important in the future.
There is a significant opportunity in smaller commercial buildings to improve energy efficiency and reduce energy bills. Retrofitting building automation systems that address the unique needs of smaller buildings is an important tool in reducing their energy consumption. Such small building energy management systems are now commercially available, and more companies will deploy them in the future to counter the ever rising cost of energy in buildings.
