ASHRAE 135 BACnet Update: What Engineers Need to Know

ASHRAE published the 2025 revision of Standard 135 — the governing specification for BACnet — with several notable changes that affect how devices are profiled and how BACnet/SC networks are structured. Here's what design engineers and commissioning agents should be aware of before their next BAS specification.

BACnet/SC Changes

BACnet Secure Connect (BACnet/SC) sees expanded mandatory requirements in the 2025 revision. Devices claiming BACnet/SC compliance must now support direct connections without relying solely on a hub, improving resilience in distributed systems. The revision also clarifies certificate management procedures, which had been a source of confusion in earlier implementations.

Device Profile Updates

Several device profile designations have been updated. The B-ASC (Advanced Application Specific Controller) profile now has stricter object support requirements. Verify with your controller manufacturer that their firmware revision aligns with the 2025 standard if your specification explicitly cites it.

Engineers writing BACnet specs should confirm whether they're citing the 2022 or 2025 version of 135, as the two are not fully interchangeable in terms of device profiles.