Designing a BACnet based Building Management System (BMS)
Modern buildings are getting smarter with every technological advancement. Many corporate houses and commercial buildings are equipped with a system that automatically adjusts temperature and light based on occupancy, and even predicts when equipment needs maintenance. Behind all this automation, Building Management Systems (BMS) control all operations with minimal human intervention.
But not all building management systems devices or appliances work the same way. Some communicate through different languages/connections, and some cannot talk to each other. It is like trying to coordinate a team where everyone speaks a different dialect and sometimes works in isolation.
This is where BACnet comes in, it enables BMS to control things and communicate by using different physical and network layers standards, such as IP, Ethernet, and MS/TP, to transmit standardized service requests and replies between devices. By bridging different communication protocols, BMS allows seamless interoperability and centralized management.
The importance of BACnet in BMS is underscored by the industry’s rapid growth. The Global Market Insights states that the building management systems market across the globe is anticipated to grow from USD 23.29 billion in 2025 to approximately USD 82 billion by 2034, at a Compound Annual Growth Rate (CAGR) of around 15%. And, in the US, particularly within the North American market, which accounted for 34.2% market share in 2024, growth is driven primarily by rising demand for energy efficiency, compliance with green building certifications, and ongoing smart city initiatives.
What is BACnet?
BACnet is an open standard based on American National Standard ASHRAE 135, built for building automation.
BACnet shows up in different forms. BACnet/IP for Ethernet, BACnet MS/TP for RS-485 wiring, and the newer BACnet/SC (Secure Connect), which finally brings stronger security, lets different devices communicate regardless of manufacturer. The HVAC system from Company A can now work seamlessly with lighting controls from Company B.
In modern embedded hardware design, BACnet functionality is often implemented directly within controllers and field devices, enabling real-time communication and interoperability across systems. A BACnet in BMS includes controllers that make decisions, field devices like sensors and actuators, communication networks, and management dashboards. When everything speaks BACnet, integration becomes straightforward instead of a custom engineering project.
This differs from older proprietary systems. Remember when one could not use certain apps because they only worked on specific phones? Building automation faced the same problem until BACnet provided a common language.
Architecture of a Building Management System with BACnet
A BACnet integrated BMS can be structured into four key layers, each responsible for a distinct function:
- Field Devices: These include sensors, actuators, energy meters, and local controllers that interact directly with the physical environment
- Communication Layer: This comprises the networking infrastructure, such as BACnet/IP over Ethernet or BACnet MS/TP over RS-485. Gateways are often incorporated to bridge legacy or proprietary systems
- Supervisory Layer: At this level, servers, databases, and visualization dashboards consolidate information, enabling monitoring, reporting, and informed decision-making
- Application Layer: The highest level of the system, where automation logic, analytics, and cloud-based integrations happen. This layer provides the intelligence required for optimization and advanced management
Layered architecture of BACnet based Building Management System
Hardware Design for BMS using BACnet
Designing the hardware architecture for a BMS using BACnet requires industrial-grade controllers and designing edge devices that can handle continuous 24/7 operation. Typical deployments utilize ARM Cortex-M microcontrollers for the field controller and x86-based industrial PCs for supervisory layers. Controllers connect with sensors, actuators, and relays to manage HVAC, lighting, energy, and security.
The communication backbone often combines BACnet/IP over Ethernet for high-speed data exchange with BACnet MS/TP over RS-485 for field devices. To maintain reliability, especially in critical facilities, redundant switches, dual-NIC gateways, and UPS-backed controllers are standard. Supervisory servers usually operate with RAID storage for data redundancy, and in many cases, virtualization is used to separate workloads and improve modular scalability.
Software & system design for BMS
Controllers run real-time OS such as VxWorks, FreeRTOS, or QNX, hosting BACnet stacks that handle real-time device control, Read/Write Property commands, and notifications.
Supervisory servers run BMS middleware and applications on Windows or Linux. They manage device discovery, polling, logging, and analytics. Data is stored in SQL or time-series databases, and dashboards present actionable insights. Open APIs allow integration with enterprise systems, cloud platforms, or IoT devices.
Field devices communicate via BACnet to controllers, which normalize data and forward it to servers. The software stack ensures interoperability, real-time control, and analytics while maintaining security with BACnet/SC and role-based access.
Cloud integration and security challenges
Connecting BMS frameworks to the cloud enables remote monitoring, large-scale analytics, and integration with enterprise or IoT platforms. This is now a mainstream BMS expectation, but it also brings new design and operational complexities.
Exposing BMS systems to the internet introduces new security risks, requiring uncompromised solutions such as BACnet/SC, encrypted communication, strong user authentication, and continuous monitoring for vulnerabilities.
Key design principles for BACnet-integrated BMS
- Interoperability: Ensure the system can support multiple vendors and subsystems without custom fixes
- Scalability: The design should allow easy expansion, from a single building to a multi-site campus
- Flexibility: Legacy systems will not disappear overnight. The gateways help bring them into the modern network
- Cybersecurity: With buildings connected to IT networks, security is non-negotiable. BACnet/SC, encryption, and secure access controls are vital
- Resilience: The BMS must be able to withstand failures. Backup systems and failover mechanisms ensure continuity
Integrating subsystems into a BMS with BACnet
The real value of BMS lies in integrating diverse subsystems under one platform.
This includes HVAC for automated climate control, lighting systems that adjust based on occupancy and daylight, energy management to optimize electricity use and integrate renewables, security and access control systems like CCTV and fire alarms, as well as elevators and other facility services.
Collectively, these integrated subsystems offer a unified view of building health and performance, enabling improved operational efficiency and smarter decision-making.
Future of BACnet based BMS
The future of BACnet based BMS will be shaped by tighter security, more intelligent automation, and sustainability goals. The adoption of BACnet Secure Connect (SC) is expected to become standard, while IPv6 support will allow much larger and more connected device networks. At the same time, convergence with IoT standards such as Matter and OPC UA will enable seamless interoperability across a wide range of building systems.
Artificial intelligence will play a central role by predicting equipment failures, optimizing energy consumption, and dynamically adjusting environments in real time. Digital twins, which are virtual representations of entire buildings, are emerging as powerful tools that allow operators to simulate and predict system behavior before implementing changes in the physical environment. Above all, sustainability will remain the key driver, and with BACnet, BMS will actively manage energy demand, renewable energy integration, and carbon-neutral initiatives.
To conclude, a BACnet in BMS is a smarter and safer way to make efficient buildings. Focusing on interoperability, scalability, and security ensures systems can meet current needs while adapting to future demands.
MosChip® offers end-to-end engineering capabilities to design and develop solutions for Building Management Systems (BMS), leveraging deep expertise in embedded hardware, system engineering, and software integration. Our capabilities include scalable BMS controllers, including sensor, actuator interfaces, communication gateways, and integrated edge modules. These solutions enable BACnet compatible architectures that provide real-time control, secure connectivity, accurate data acquisition, and seamless interoperability across HVAC, lighting, and access control subsystems, while supporting integration with multi-vendor devices.
To see a live demo of BACnet-based BMS, meet our team at Embedded World North America 2025, Booth #4068 in Anaheim, CA.
Schedule a meeting with us, and our team will give you a guided walkthrough of some of our innovations.
