Building Management System vs Building Automation System

What is the difference between a Building Management System (BMS) and a Building Automation System (BAS)?

The simple answer is that there is no differentiation between BMS and BMS.  The two terms are frequently used interchangeably in the industry.  For some time, vendors were trying to differentiate Building Automation Systems as an advanced version of Building Management Systems. But then everybody started to call their BMS a BAS.

The software vendors looked at BAS as an evolution to BMS systems by adding smarter analytics and advanced automated controls.  However, the building owners and operators view BAS as a subset to BMS with a focus on automating HVAC and Lighting controls.

Two other terms that are synonymous with BMS are Building Control Systems (BCS) and Energy Management Systems (EMS/EMCS).

What is the difference between?

  • BMS – Building Management Systems
  • BAS – Building Automation Systems
  • BEMS – Building Energy Management Systems
  • EMS – Energy Management Systems
  • EMCS – Energy Management Control Systems
  • EPMS – Energy Power Management Systems

These various terms all had separate origins, and today you may find small nuances between software vendors still using each of these terms.  From the industry perspective, BMS is the primary term used.  The larger primary vendors, such as Carrier, Eaton, Honeywell, Johnson Control, Schneider Electric, and Siemens, have sophisticated (and in many cases multiple variants) offerings and are truly comprehensive Building Management Systems.  Smaller vendors may specialize in specific areas of power management, power distribution, cooling, and thermal control, but not the various other components the larger vendors do.

What is a Building Management System?

The BMS's core function is to manage the internal environmental conditions within a building, i.e., temperature, in a way that is as energy-efficient as possible.

A Building Management System (BMS) is a computer-based system installed in buildings to control and monitor mechanical and electrical plants, including; HVAC (heating, ventilation, air conditioning), lighting, power systems, fire systems, and security systems.

Effective well-utilized Building Management Systems (BMS) provides the core management tool required by building managers to ensure monitoring and efficient management of energy and occupant comfort. It enables Building Managers to provide the optimal working environment while minimizing the landlords' and tenants' costs. Effective BMS utilization allows for optimal building performance by extending equipment and systems' operational life by reducing loads and operating hours. Therefore, maintenance and capital costs are reduced, and less embedded energy is consumed through equipment replacement and upgrades.

When a building has been completed, its structure's impact on its energy consumption performance is usually fixed until refurbishment occurs. However, base Building and Tenant Light and Power energy consumption can be increased or decreased by the performance of both building systems and tenants. A BMS will show increases in energy use due to equipment failure or adjustments to operating parameters. For example, heating valves open when the building requires cooling or whole floors of lights for extended periods due to cleaning activity.

A BMS may also indicate that air-conditioning is starting up hours before the building is fully occupied due to security staff activities. With this information in hand, the building manager may rectify such issues through consultation or engineering solutions.

Additionally, a BMS may not react quickly enough to changes in data center computing demands as application workloads spin up or down.  The introduction of new equipment will also change power draw and thermal dynamics.

In the absence of a BMS, the impact of such events can be disguised by seasonal variations, changes in occupancy levels, or technology upgrades. A correctly configured BMS with an adequate number of precisely located monitoring points is the only way a building manager can quickly alert problems that could otherwise remain undetected until annual inspections or external audits are undertaken.

A BMS is also a primary tool for identifying energy intensity improvement opportunities, for example, refining the size and number of lighting time blocks, providing meaningful reports to the Building Management Committee on issues and opportunities, and enabling identification of faults, maintenance planning, and energy-saving upgrades.

Who are the major Building Control Systems vendors?

Automated Logic
- "Better buildings require intelligent solutions. We make it easy. Our solutions bring all building systems together into one cohesive ecosystem for complete control, management, and reporting. WE MAKE BUILDINGS BETTER."


EATON - “Foreseer facilitates real-time power and environmental system monitoring at a single facility or multiple locations throughout the world, helping organizations reduce power consumption costs and avoid unplanned downtime due to system failure.”


- “From technically advanced facility controls to rugged and dependable professional tools to timesaving ergonomic vacuums, Emerson has a wide array of ways to increase your facilities’ productivity, enhance their comfort and boost their efficiency.”


- “Honeywell can successfully integrate, install and maintain building management systems and provide life cycle support for facilities like yours, making it easier to increase comfort, safety and security for your occupants.”


Johnson Controls
- “Our insightful building technologies are designed to listen to what a building is saying about its condition. They collect and analyze data and then provide insights on how to improve your building’s efficiency and productivity.”


Schneider Electric
- “Our building management systems enable you to monitor, control and optimize your building’s performance throughout its lifecycle. Switch to smart building solutions with Schneider Electric Building Management Systems and Room Controllers.”

- “From single discipline systems to fully integrated buildings, whether they are small or large, single- or multi-site, whether a school, office, hospital or airport, you will find the right solution in our offering of building management systems.”


Does it make sense to integrate my BMS with other systems today?

There are two types of integration with BMS.  The first is integration between a BMS and a business management system (sometimes referred to as BI business information systems) such as an ERP (enterprise resource planning) or FP (financial planning) from SAP or Oracle.  The second is with 3rd party monitoring and management tools such as DCIM (data center infrastructure management from Nlyte)

Integration with BI systems requires a detailed configuration study. A high-level interface between such systems can be implemented if care is given to the following.

Control of data consistency in a BMS is a live system continuously updating second by second. Business management systems typically batch by day, week, month, or year.

Business management systems require data to be presented in particular formats. Interfaces between two such systems often fall over when one or the other is upgraded.

From a business perspective, the BMS often collates the data required to allocate costs to tenant business units or charge sub-tenants for services. It makes sound economic sense and reduces the probability of error for data to be migrated from one system to another, provided the costs of maintaining the interface are commensurate with the benefits.

A satisfactory alternative to a high-level interface given the routine batching needs of business systems is for the BMS to download its readings of hours run, energy used, etc. into a spreadsheet format at agreed times. The business system can typically be easily programmed to populate its data fields by interrogating the spreadsheet at agreed times.

Each system manager is then responsible when modifying or upgrading their system to ensure data moves as required. The upgrade process is particularly relevant when systems are owned and operated by different parties.

High-level interfaces between systems will seldom be cost-effective in small or medium environments.

Integration with 3rd party management tools such as DCIM, security, fire management, or individual equipment vendors was challenging.  Many systems had limited or proprietary interface protocols restricting data sharing, making it impossible to accomplish.  However, today’s key vendors support a myriad of protocols and provide API that makes it simple to export data and share data across management platforms.

There is a great benefit to these integrations:

  • A richer set of data used across multiple systems delivers accurate, efficient, and quick responses to environmental conditions and outages.
  • Real-time data are accessible by all organizations eliminating siloed data and work activities.
  • Machine learning and AI can now be applied to achieve predictive conditions that allow for reduced downtime and improved power and cooling optimization.

What is a Smart Building?

A Smart Building is one in which the essential equipment and assets, like air handlers, chillers, boilers, lighting, etc. can communicate machine-to-machine. There’s an elaborate management system in place to control and optimize all the pieces.

A Smart Building aims to deliver useful services that help make occupants more productive and safe, at the lowest cost and with the least environmental impact. A Smart Building optimizes and minimizes energy usage and can operate using clean energy sources. It makes occupant security and quality of life top priorities. These priorities mean not only physical safety, such as connected fire suppression and alarm systems, but also health security— high-quality air and water, and more.

The equipment and systems in a Smart Building need to be connected and able to communicate from machine to machine. For example, a building’s chiller could receive weather data from outside and occupancy information from inside, so it operates only when needed to maintain its occupants’ optimal temperature.

What makes all this work? The availability of small, sophisticated, affordable sensors connected via the Internet of Things (IoT) and building automation software analyzes and uses the data generated by these sensors to manage and optimize operations. Smart Building systems can use the data generated to monitor performance, track the physical location of assets, detect potential operating issues, and improve preventive maintenance efforts.

Smart buildings’ evolution starts with the first buildings ever constructed were primitive shelters made from stones, sticks, animal skins, and other natural materials. While they hardly resembled the steel and glass that make up a modern city skyline, these early structures had the same purpose - to provide a comfortable space for the people inside.

Buildings today are complex concatenations of structures, systems, and technology. Over time, each of the components inside a building has been developed and improved, allowing modern-day building owners to select lighting, security, heating, ventilation, and air conditioning systems independently as if they were putting together a home entertainment system.

Today, we seek to build, work, and live in smart buildings as the right thing to do.  Many governments and industry regulators set standards for constructing and managing facilities to meet environmental, safety, and sustainability requirements.  LEED Leadership in Energy and Design Engineering and SMaRT (Sustainable Materials Rating) are both certification program adopted by building owners and managers to certify their intent to comply with government and self-driven requirements.

Smart Buildings, which are one of the eight Smart principles behind Smart Cities, are expected to make up 7% of the total global smart city market in 2025. Smart Cities, cities that monitor all critical infrastructure conditions, including bridges, streets, water, electric systems, and more, are on the rise, as well. Frost & Sullivan estimates that by 2025, there will be more than 26 of them worldwide.

Are BMS and DCIM interchangeable?

The answer is simple: no.  The very fact that integrated data center management (IDCM) has evolved from the integration of Building Management Systems and Data Center Management Systems is proof that they are complementary technology solutions.

DCIM does address some of the facility sides of things in data center management and a few overlaps with BMS. Like a BMS, DCIM monitors power consumption of different components of the power chain, calculates PUE of the data center, monitors temperatures and hot spots, sends alerts on breach of a configured threshold, etc.

While DCIM certainly does a better job in the overlapping areas, some functions are beyond its purview and can be managed only by a BMS. For example, lighting controls, physical access controls, surveillance, fire detection, protection, and many more, and mind you, these are equally critical areas contributing to the data center infrastructure’s availability and reliability.

So the point is, it is not practically viable to replace BMS with DCIM. Instead, a more practical approach is to make the two solutions complement each other in the overall data center management as in an Integrated Data Center Management solution.  With an IDCM implementation, you derive maximum benefits from DCIM’s intelligence, analytical capabilities, and superior reporting features. At the same time, stick to BMS for gathering data from the deepest layer of the physical infrastructure of the data center.

Download a Free IDCM for Dummies eBook

Automated Logic and Nlyte Software together deliver Integrated Data Center Management (IDCM). Integration of Automated Logic WebCTRL© building automation system with Nlyte DCIM suite helps data center professionals unlock additional energy savings, reduce costs, and improve uptime in their data centers.

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