Who this is for: a facilities director choosing controls for a renovation, an expansion or a replacement, or deciding whether to stay with the current controls contractor. The decision: how open the next system should be, and what the specification has to say to keep it that way. Nothing here differs between New York and New Jersey.
The question usually arrives with a service contract
Few owners set out to choose a controls architecture. The question shows up sideways: a service renewal at a higher price, a quote for an expansion that only the original installer can provide, a contractor who no longer answers, or a new wing that has to talk to an old front end. At that point the building already has an answer to “open or proprietary,” and the owner is finding out what it costs.
Research for the Department of Energy describes large-building controls as often single-vendor and proprietary, and open standards as the way to limit vendor lock-in. Pacific Northwest National Laboratory’s interoperability review notes that misalignment between systems raises integration and maintenance costs, and that suppliers can see interoperability as a threat to their business model. No authoritative source puts a dollar figure on lock-in, and this article does not either. What it can do is show where the lock sits and how a specification removes it.
What “open” means in practice
In building automation, open usually means BACnet, the protocol defined by ANSI/ASHRAE Standard 135. The current edition is 135-2024. BACnet comes in three common forms:
- MS/TP, on twisted-pair field wiring between controllers. Speeds of 9,600 and 38,400 baud are required and run up to about 4,000 feet per segment; 115,200 baud is optional and limited to about 3,280 feet. Many field devices support only the two required speeds.
- BACnet/IP, over the building’s IP network, which scales across subnets at much higher speed.
- BACnet Secure Connect (BACnet/SC), which carries BACnet over TLS-encrypted, authenticated connections. It has been part of the standard since the 2020 edition, and BACnet Testing Laboratories has tested it since December 2022.
Speaking BACnet is the starting point. Interoperability is specified in more detail than that. Every BACnet device must have a Protocol Implementation Conformance Statement (PICS) listing the functions it supports, grouped into standard building blocks and device profiles: an operator workstation, a building controller, an application-specific controller and so on. A BTL listing tells you which of those functions a device passed testing for, and no more. The PICS on the BTL site is the manufacturer’s own statement, which BTL does not verify. One BTL-listed application-specific controller, for example, was tested only for reading, writing and device management, with nothing for scheduling, trending or alarms. If the building needs a controller to hold a schedule or log a trend, check that those functions are among the ones tested.
Gateways deserve the same scrutiny. A gateway translates between a manufacturer’s own protocol and BACnet, and it can only pass along what the device reports. As a NIST researcher put it in ASHRAE Journal, gateways have a limited ability to translate dissimilar concepts, and the trouble shows up in schedules, alarms, prioritized commands and trend data. A system that is open at the front end and proprietary behind gateways is open in name more than in practice.
An open framework can still be locked
Niagara, from Tridium, is a framework many buildings use to integrate equipment from different manufacturers, and ieComfort is Niagara 4 certified. It is an open framework. It also carries a licensing mechanism that can close it.
Every Niagara license includes a compatibility statement, which Tridium calls the Niagara Information and Conformance Statement (NICS; older documents say Niagara Compatibility Statement). Each station and engineering tool carries a brand identifier, and four fields set which brands may exchange data with a station and which brands’ engineering tools may connect to it and change its programming. Each field can allow one brand, a list of brands, none, or all. Tridium’s own documentation describes a “fully restricted system,” in which the stations and tools work only with the same brand. A building can run on Niagara and still be serviceable by one contractor’s tools.
Tridium also publishes the fix. Its suggested specification language sets all four fields to accept every brand, preserves the owner’s right to have any license modified regardless of supplier, bars brand-specific software that other Niagara tools cannot open, and gives the owner every platform and station login at the end of the project.
Two dates matter for anyone buying or renewing Niagara now. Niagara 4.15 is the last Niagara 4 release and is supported through 2028. Tridium is targeting Niagara 5 for December 2026, and supervisors and JACE-9000 controllers need an active software maintenance agreement to move to it. A lapsed maintenance agreement is worth finding out about before it limits the upgrade path.
When proprietary is a reasonable choice
For most institutional and multi-building owners we think open is the better default, but a single-vendor system is not automatically a mistake. One manufacturer can answer for the whole system, from controllers to graphics to service. Packaged equipment often arrives with its own controls, and Tridium’s documentation acknowledges that an equipment maker may want other systems to read its data while keeping engineering access to itself, to protect the equipment. And an owner with a large investment in one platform and a contractor who performs well may reasonably decide that migration costs more than it returns.
Some large New York City institutions take a middle path. Columbia University’s controls standard requires BACnet so that different manufacturers can interoperate, but does not permit substitutions outside its approved vendors; Weill Cornell Medicine’s standard requires open BACnet communication while limiting bidders to an approved list. The protocol stays open while the owner controls who works on it.
What makes any of these choices sound is that the owner holds the keys: the licenses, the passwords, the programming tools and the project files. A proprietary system with all of those in the owner’s hands is in a far better position than an “open” one without them.
What to write into the specification
Owners who want an open system write it into the specification. The first five items below appear, in one form or another, in the published controls standards of public owners such as the University of Kentucky, Dartmouth and the City of Toronto; the rest follow from the sections above.
- Licenses in the owner’s name, perpetual and transferable, for every software component: the front end, the supervisory platform and any metering or lighting integration.
- Every credential. Administrator, programming and factory-level usernames and passwords, delivered at turnover. No hard-coded credentials.
- The tools and the files. The engineering software needed to program the controllers, the project databases, graphics and any custom code.
- Open protocols to the controller. BACnet/IP at the network level and BACnet MS/TP or IP at the field level, with no proprietary protocols or gateways between the supervisory system and the controllers it manages.
- Open licensing. On Niagara, all four NICS fields set to accept every brand, and no brand-specific software.
- Proof of interoperability. A PICS and a current BTL listing for each device type, with the functions the building needs (scheduling, trending, alarming) among those tested.
- Security. BACnet Secure Connect where the equipment supports it, and a network design approved by whoever owns the building’s IT.
- Usable data. Consistent point naming and tagging. Project Haystack and Brick are in use today, and ASHRAE Standard 223 is in its final public review. Where sequences are written new, ASHRAE Guideline 36-2024 provides standard high-performance sequences of operation.
Security belongs in the same conversation
Plain BACnet/IP has no built-in authentication or encryption. A March 2026 CISA advisory on one commercial building controls platform put it directly: systems that communicate over BACnet inherit the protocol’s lack of network-layer authentication. CISA’s guidance for building controls is to keep them off the internet, behind firewalls and separate from business networks, and to move to BACnet Secure Connect where the equipment supports it. The General Services Administration, which runs federal buildings, prefers BACnet Secure Connect over older BACnet connections and requires devices to have no hard-coded credentials. An open system is easier to secure when the owner holds the credentials and knows what is on the network.
A short decision path
Observe
Take inventory before deciding anything: which controllers and protocols are installed at each level, which gateways sit between them, who holds the licenses and passwords, whether Niagara stations are brand-restricted, and whether the maintenance agreement is current.
Decide
Choose among three paths: stay with the current platform and secure the owner’s keys; open up in place by re-licensing, adding BACnet integration and replacing the worst gateways; or migrate over time, starting where equipment is due for replacement anyway.
Act
Write the choice into the specification and the contract, using the items above.
Verify
At turnover, check the BTL listings against what the building needs, confirm the licenses are in the owner’s name and the NICS fields are open, and test that the credentials and tools you were handed work.
The next step
Start with an open controls roadmap. Send the most recent controls service contract or invoice, the equipment list, and either the BAS point list or a few screenshots of the front end. The review returns a compatibility and migration decision: what can be opened in place, what cannot, and what a specification for the next phase needs to say. It may conclude that staying with the current platform, with the owner holding the keys, is the right answer. Send the building details (until the screening tool is live, this is a short intake form).
Parent guide: Your BAS Is Running. That Doesn’t Mean Your Building Is Operating Correctly. Related reading: Controls and building automation in New York and New Jersey
Sources and dates
- ANSI/ASHRAE Standard 135-2024 (BACnet), announced by BACnet International, December 2024; Addendum 135-2008ab (MS/TP baud rates); Addendum 135-2016bm (MS/TP unit loads); Addendum 135-2016bj (BACnet Secure Connect, approved November 18, 2019); IETF RFC 8163 (2017).
- BACnet Testing Laboratories: listing program, BTL Mark Certification Standards (May 2025), Test Package 23 (December 2022); bacnet.org FAQ on PICS and device profiles; ASHRAE Addendum 135-1995d (BIBBs and device profiles).
- S. Bushby (NIST), “Communication Gateways: Friend or Foe?”, ASHRAE Journal 40(4), April 1998.
- Tridium, “Niagara Information and Conformance Statement (NICS),” document 2022-0017; Tridium Niagara 5 FAQ (2026).
- Owner standards: University of Kentucky, Division 25 Integrated Automation (rev. 02/26); Dartmouth College, 25 00 00 Integrated Automation (January 2023); City of Toronto, Standard BAS Specification for City Buildings (2018); University of Houston, 25 15 00 (2018); Columbia University, 23 09 00 (2018); Weill Cornell Medicine BMS standard (2020).
- CISA advisory ICSA-26-078-08 (March 19, 2026); CISA, FBI, EPA and DOE, “Primary Mitigations to Reduce Cyber Threats to Operational Technology” (May 6, 2025); GSA CIO-IT Security-16-76 Rev. 4 (March 25, 2024); NIST SP 800-82 Rev. 3 (September 2023).
- Pacific Northwest National Laboratory, Buildings Interoperability Landscape, PNNL-24089 (draft, February 2015); PNNL-34399 (May 2023).
- ASHRAE Standards Actions (Standard 223P public reviews, 2025 and 2026); Project Haystack; Brick Schema; ASHRAE Guideline 36-2024.
- Last reviewed October 28, 2026. Next review January 15, 2027, to update the Niagara 5 and ASHRAE 223 status.