What you will learn from this Building Automation Systems article:

  1. The efficiency and conveniences Building Automation Systems add to the building control systems and HVAC systems
  2. How Building Automation enhances building energy savings and troubleshooting problems
  3. How allowing controllers to communicate with each other enhances HVAC and electrical systems
  4. Many of the benefits of Building Automation Systems for Building Automation and Building Control Systems
  5. Communication Protocols and Integration of HVAC Systems, Lighting, and other Building Control Systems
  6. Building Control System User Interface for Remote Monitoring and Control
  7. Monitoring Energy Consumption and Energy Efficiency
  8. Lastly, resource and Related Links to help you learn more

Many people wonder what Building Automation Systems (BAS) can do. The primary use of BAS is commercial HVAC control systems and energy management system applications. Building Automation itself is an energy management system that saves management companies and building owners by efficiently controlling air conditioning and heating comfort and process systems.

What is Building Automation Systems in HVAC

A building automation system (BAS) is the centralized automatic digital control of a building’s HVAC, lighting, security, and other systems through a BAS or building management system (BMS). BAS should increase building energy efficiency and reduce maintenance costs versus buildings without BAS.

BAS is where mechanical and electrical systems and equipment connect with microprocessors that communicate with each other and possibly to a computer. Additionally, these computers and controllers in the smart building can be networked to the internet or serve as a stand-alone system for the local peer-to-peer controller network only. Additionally, the digital controllers themselves do not need a computer to process the control functions as the controllers have their internal processors.

Related Link: Learn more about DDC control loops (opens in a new window)

Tridium Controllers for Data Center

Tridium Controllers for Data Center

Engineering the Controls | How Do Building Automation Systems Work?

Set-up in a multi-story automated smart building would have many controllers serving different types of air conditioning and heating equipment (BAS is not limited to just HVAC applications). Every building is different, and the BAS engineer needs to select the proper HVAC control systems and programs to control the various types of equipment in a particular automated building.

For the smart building to be effective, the BAS must be installed and tuned properly. Some advantages of a good building management system are:

Basic Checklist
  1. Equipment/Lighting Scheduling
  2. Optimal Start
  3. Trip and Respond
  4. Energy Use Monitoring
  5. Precise Economizer Control
  6. Predictive Control
  7. Load Shedding (Peak Shaving)
  8. Building Operator Alerts
  9. Billing/Tracking Tenant Energy Use
  10. Integration
Detailed Checklist


Equipment/Lighting Scheduling

BAS should allow the owner to set up schedules of operation for the equipment and lighting systems so that energy savings can be realized when the building or spaces in the building are unoccupied. This reduces runtime and power output saving in both energy consumption and maintenance costs.

Optimal Start

BAS should allow the equipment “optimal start” with adaptive learning. “Optimal start” is allowing the equipment to be brought on in an ordered and sequential manner automatically on a schedule before the building is reoccupied so that space set points can be realized before occupation.

Additionally, adaptive learning allows the system to compare space temperature, outside air conditions, and equipment capabilities so that the equipment can be turned on at an appropriate time to ensure space setpoints are achieved before occupation.

Trim and Respond

BAS control systems should have “trim and respond” capabilities. Based on zone demand, the setpoint for various heating and cooling sources will change according to demand from the zones. In a VAV system, all the VAV boxes are served from a central air handling unit. Moreover, if all the zones are at the setpoint, then the supply air temperature setpoint of the air handler is automatically changed to prevent mechanical cooling from occurring when it is unnecessary.

Furthermore, when the zones grow warmer, the supply air temperature setpoint is automatically lowered to allow mechanical cooling to satisfy demand. Finally, older systems have a single supply air temperature setpoint of 55° Fahrenheit, which requires the compressors to cycle even when it is not necessary.

Energy Use Monitoring

BAS should have the ability to monitor energy usage, including the ability to meter electric, gas, water, steam, hot water, chilled water, and fuel oil services.

Precise Economizer Control

BAS in conjunction with the appropriate mechanical system set-up should offer to economize based on enthalpy calculations or CO2 setpoint control.

Predictive Control

BAS should have such BAS control algorithms as reset schedules for heating plants, static pressure control, and other systems where energy savings can be realized through these predictive programs.

Load Shedding (Peak Shaving)

BAS should offer load shedding when power companies are at peak demand and need business and industry to cut back on power usage to prevent brownouts. Building Automation Systems allow the owner to cycle various things off like water heaters or drinking fountains where the use of these things will not be noticed even though they are off.

Building Operator Alerts

Building Automation Systems should offer the ability to send alarms via email, pager, or telephone to alert building managers or technicians of developing problems and system failures.

Billing/Tracking Tenant Energy Use

Management companies who acquire a good control system can have the system set up to bill tenants for energy usage.


BAS should have the communications abilities to be integrated with other control systems and TCP/IP. BACnet compatible or other open-source communication protocol is a plus.

How Does a Building Automation System Work?

Building Controlled by BAS

Modern buildings typically have central HVAC plants to provide heating and cooling for the entire building. Furthermore, some highrise buildings can have several central plants either in the basement, on various floors, or on the roof of the building.

Additionally, institutional buildings also, to some degree, have central plants that provide heating and cooling for the buildings that are spread out over campus. In the old days, before building automation systems, these systems were not integrated.

These non-integrated systems were very inefficient, and this resulted in energy hogs. While following is a simplistic answer to the question, “how a building automation system works,” it demonstrates one of the many ways building automation systems save money by reducing energy use.

Furthermore, BAS allows all these systems integration between controllers, the internet, and the BAS server. Additionally, they allow precise control based on several factors, including weather conditions, demand factors of occupation, and other variables down to the micro-level that allow for the systems to be very energy efficient. In the old days, a central plant would maintain a chilled water temperature of 55° F.

Now, with BAS and precise computer control, that setpoint temperature can be changed when certain conditions exist. If, say, in the Spring or Fall, the temperature outdoors is 48° F and only a quarter of the local fan coil units are calling for cooling, the intelligent response of BAS involves increasing the setpoint temperature for the central plant chillers.

Additionally, the economizers can pull in outside air to satisfy the demand for cooling from the local fan coil units. That decreases energy consumption via mechanical cooling. Finally, that utilizes outside air (free cooling) and minimizes the runtime for the chilled water plant.

How does BAS Work with Electrical Systems?

Building Automation Systems Lighting ControlAs BAS works with mechanical systems integration can occur with building electrical infrastructure such as lighting. In a typical campus environment or office buildings, there are typical times of high occupancy. During these times, you want the lighting systems to work normally.

After hours, when everyone has gone home, you want the lights to be off. Some people forget or haphazardly leave lights on. When digital integration occurs into the lighting system, time can be programmed into the system to turn the lights off for most of the building.

At the same time, because some people work late or possibly the cleaning staff, you want the lights to work. Therefore, overrides for the lighting system are programmed, so when someone turns on the switch, the lights come on. However, when the Building Automation Systems is on an override, a timer begins once the light has been turned on.

Therefore, after a few hours (or whatever programmed time is input into the system), the light goes out. Motion sensors can also be utilized to let the system know to turn the lights on when someone enters the room. Additionally, after they depart, and the motion sensor senses no motion, the lights extinguish. Finally, that also functions well with parking lot lighting based on sunrise and sunset parameters.

System Architecture | Network Structure

Building Automation System Architecture

Basic List of Communication Protocols for BAS

  • BACnet
  • LONtalk
  • MSTP
  • DALI (lighting)
  • Zigbee (wireless network)
  • MODbus

Related Link: How DDC Status Works to monitor motors, pumps, and other processes.

Building Automation Systems Integration for HVAC Systems

Facility managers and occupants (if permitted through demand response) can make changes for improving occupant comfort. The facility manager, along with permitted operators typically has the most control over the system. Integration into HVAC systems and lighting controls saves building energy over older types of control systems. Additionally, integration can be done for (not all-inclusive):

Building Automation Systems | HVAC Control

There are many other examples of how digital control can help you especially if you manage large building(s) even if the buildings are next door to each other or on the other side of the world Building Automation Systems can be linked to a central computer over the internet.

If I’m a corporate engineer in Dallas, and there are 25 buildings all over the states, I can monitor and control all those buildings from any computer with an internet connection. Everything from schedules to energy consumption to potential problems. To improve energy efficiency and reduce energy consumption I can set up trends that will produce data tables. Analyzing that information, I can make minor adjustments that will reduce energy consumption and save money.

It only gets better as time goes on, but modern smart building control systems are helping to reduce energy usage and enhance buildings by making the electrical and mechanical systems efficient and smart.

Additional Benefits of BAS Control | What Does a BMS System Do?

  • HVAC Systems – All processes are automatic and set to a DDC program in the controls. A computer and proprietary software and hardware accomplish these tasks. Three distinct protocols are shared by different manufacturers so that systems integration can occur.

Additionally, there are bridge programs that integrate the different DDC protocols, so points are read into different DDC software programs. Outside air and humidity can be read and applied to energy-saving programs within the Building Automation Systems.

Thermostat set points can be restricted, preventing occupants from adjusting the thermostats outside of the restricted range. Furthermore, schedules input into the DDC program, so in unoccupied times, all non-essential HVAC Systems shut down.

  • Lighting Systems – lighting systems, both inside and outside, can be set to a schedule, so in unoccupied hours minimal lighting is on. Motion sensors can also be hooked up to DDC and monitored for usage. Finally, programs can be set up to bill tenants for energy use for lighting and other energy-consuming systems.
  • Emergency Systems – modern energy management systems can also control and monitor emergency systems. Fire alarms and stairwell pressurization, along with security systems, can be integrated into the DDC control system to automatically control critical emergency processes and alert necessary personnel in the event of an emergency.
  • Security and access control systems

Alternate Names for Building Automation Systems

You may get a little confused if you happen to talk to someone and use a different name for modern BAS. Some people use the term loosely and sometimes incorrectly. Therefore, it is a good idea to familiarize yourself with the terminology so you avoid confusion. Here are some names that essentially mean the same and do the same thing:

  • Building Monitoring System or BMS - this is a commonly used name in place of BAS.
  • Energy Management System or EMS
  • Distributed Control System or DCS
  • Direct Digital Controls or DDC
  • Building Control System or BCS

All these names can describe BAS. They are essentially the same thing. Computer controls connected through a network controlling HVAC, Lighting, and Security systems. That can also include Life and Health systems. The connections are typically over different types of networks and communication protocols. DDC systems are different from PLC (Programmable Logic Controllers) systems but they can be integrated into BAS.


Related Link: Learn more about Direct Digital Controls and examples of programming, or you can also see our Direct Digital Controls category.

HVAC Infrastructure for BAS

Equipment digital control is typically DDC but can be the equipment manufacturer’s controls where DDC is integrated. Various inputs and outputs connect the controllers to the equipment wirelessly or with wiring. Sometimes this is by dry contacts and sometimes this is done by connecting points the DDC reads and delivers throughout the network. This all depends on the HVAC equipment and if the equipment has communication abilities. All controllers have various functions in their programs for the equipment. For example, a controller can have all the programming for the equipment they control. The program once set up properly, will allow the equipment to be monitored and controlled efficiently. The controller also has various levels of operation. The levels of operation include:

  • Occupied Mode
  • Unoccupied Mode
  • Morning Warm-up Mode
  • Setback Mode for Night

Another remote controller, may set the schedule and communicate to the slave controllers to sleep, wake up, or commence morning warmup. A good control system will allow for an optimized start to bring all the equipment on in a specific sequence that is efficient and effective. Another good thing about an optimized start for a control system is the ability to learn the equipment and its limitations. If it is 0° outside it knows it needs to start the sequence earlier to reach set points than if it is 70° outside. This feature offers added efficiency and comfort. These systems offer precision control and monitoring for building managers all through a computer user interface. This saves time and reduces energy and maintenance costs.

High Performance HVAC

Your Resource for HVAC Controls – Building Automation Systems Information

The video below is a futuristic look at how Building Automation System BAS is developing for the next generation in building controls.