Episode Description:
BACnet over SC is increasingly appearing in specs, submittals, and IT conversations. If you work with BAS networks, this episode helps you understand what is changing and what stays the same, so you can walk into the next project with confidence.
You’ll hear why legacy BACnet/IP assumptions are colliding with modern IT expectations, how Secure Connect shifts communication patterns, and what that means for troubleshooting when things stop talking. It also sets clear boundaries between a true standard and vendor marketing language, so you can ask better questions before deployment.
Topics Covered
If you want to be ready for the next Division 25 driven jobor the next IT security review, this is the one to queue up.
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BACnet over SC is becoming a core topic in building automation projects as cybersecurity requirements continue to tighten. Owners, IT departments, and specifications are no longer satisfied with assumptions that BAS networks are isolated and trusted. This shift has pushed the industry toward a more secure, structured approach to moving BACnet traffic across modern networks.
This article explains why BACnet over SC was created, how it works in practice, and what it means for technicians, engineers, and project teams working in the field.
BACnet over IP was designed when building automation networks were typically isolated behind firewalls and rarely connected to enterprise systems. The original model assumed that any device on the subnet could be trusted. Communication relied on UDP, broadcast discovery, and plain text messaging.
As buildings became more interconnected, these assumptions no longer held. Encrypted traffic is now expected by default. Device authentication and auditability are standard requirements in most IT environments. BACnet over IP does not meet these expectations on its own, creating a need for a secure transport that can operate naturally across routed networks.
BACnet over SC was developed to address these gaps without changing the BACnet services and objects that systems already rely on.
BACnet/IP traffic is transmitted in plain text. With basic packet capture tools, commands, schedules, object values, and user data can be read directly from the network. This exposes operational data and potentially sensitive information to anyone with access to the traffic.
There is also no built-in device authentication. Controllers trust messages based solely on IP addresses. A rogue or misconfigured device can impersonate a legitimate controller without being verified.
Broadcast dependency creates additional challenges. Who-Is and I-Am messages flood the subnet, and as systems grow, broadcast traffic increases. Routed networks and firewalls often block this traffic, leading to complex BBMD configurations that are easy to mismanage and difficult to troubleshoot.
BACnet/IP relies on UDP for communication. This approach is fast but connectionless and unencrypted. Discovery depends on broadcast messaging, which works best on flat networks.
When systems span multiple subnets, BBMDs must forward broadcasts. These require manual configuration and ongoing maintenance. Any change in addressing or network structure can disrupt communication if tables are not updated correctly.
Security in BACnet/IP environments is largely external. Firewalls and routers protect the network, but the devices themselves are not authenticated.
BACnet over SC is a secure transport for BACnet traffic. The BACnet protocol itself does not change. Services and objects remain the same. What changes is the transport layer.
Secure Connect replaces UDP-based BACnet/IP communication with TCP and TLS encryption. All communication is connection-oriented, encrypted, and authenticated. There is no unsecured mode.
Because it uses TCP, BACnet over SC works naturally across routed networks and aligns with modern IT practices.
BACnet over SC introduces a hub-based architecture. All devices establish secure TCP connections with a hub rather than communicating directly with one another.
The hub acts as a central message broker. It routes encrypted BACnet messages between devices. Field controllers, supervisors, and servers can participate as BACnet over SC devices, but communication always passes through the hub.
Each device uses digital certificates and private keys to establish identity. Mutual authentication ensures that devices trust the hub and the hub trusts the devices.
Redundancy options allow multiple hubs to be configured. If a primary hub fails, a secondary hub can take over message routing, providing fault tolerance that many traditional BAS architectures lack.
BACnet over SC is a standardized, vendor-neutral protocol defined by ASHRAE. It secures the BACnet transport layer.
Secure BACnet is a vendor-specific term that typically refers to proprietary encryption methods or VPN tunnels wrapped around traditional BACnet/IP traffic. While these approaches can improve security, they are not standardized and may limit interoperability.
BACnet over SC provides security as part of the protocol rather than as an external add-on.
BACnet over SC does not replace BACnet/IP. Both can coexist in the same system. Gateways can bridge traffic between them, which allows phased migrations.
It is not plug and play. Certificate management and trust configuration are required before devices can communicate.
Networking fundamentals still matter. IP addressing, routing, firewall rules, and port management remain critical to system operation.
Digital certificates provide each device with a unique cryptographic identity. Devices only communicate with other devices they trust.
Certificates can be issued by third-party certificate authorities, customer IT departments, or generated internally through self-signed methods, depending on project requirements.
Trust stores define which certificates are accepted. Devices without trusted certificates are rejected.
Certificates expire and must be renewed. Lifecycle management is essential to prevent unexpected outages.
All traffic is encrypted using TLS, preventing packet sniffing and data exposure.
Mutual authentication ensures that only trusted devices can communicate.
Integrity protection prevents message tampering and command manipulation.
The hub-based model centralizes security enforcement and message routing.
Technicians will need stronger networking knowledge, including TCP/IP fundamentals, ports, and firewall behavior.
Certificate management becomes an operational responsibility. This includes generating certificates, importing trust chains, tracking expiration dates, and coordinating with IT departments when required.
Troubleshooting shifts toward software, security, and trust relationships rather than physical wiring issues.
Logs become critical tools for diagnosing certificate and connection problems.
BACnet over SC is commonly specified in large campuses, healthcare facilities, airports, and universities.
Division 25 specifications increasingly require secure BAS communication, making BACnet over SC a frequent requirement.
It is well-suited for routed networks and remote access environments where encrypted communication is expected.
BACnet over SC represents a fundamental shift in how building automation systems communicate across modern networks. It aligns BAS infrastructure with current cybersecurity expectations while preserving the BACnet functionality the industry depends on.
For professionals seeking to develop new skills in networking and certificate management, BACnet over SC provides a more secure, scalable foundation for future systems.
For a deeper discussion and insights from the field, listen to this episode on the Smart Buildings Academy podcast.