The BACnet standard was developed and is maintained under the auspices of ASHRAE SSPC 135, the BACnet Committee. BACnet International is an industry association that facilitates the successful use of the BACnet protocol through interoperability testing, educational programs, and promotional activities. It also oversees operation of the BACnet Testing Laboratories (BTL) and maintains a global listing of tested products. This article is going to explore BACnet from the viewpoint that the standard is applied by developers to create devices, networks, and applications, i.e., “Things” that participate in the open BACnet ecosystem.
Before jumping into the details, let’s set the stage for a discussion of the concept of open systems.
The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard communication protocols.1 This is why BACnet products from different manufacturers can successfully work with each other to produce best-of-breed solutions.
In 1984, the ISO (International Organization for Standardization) published this Model. The OSI Model has seven different layers, divided into two groups.
It is important to emphasize that this is a conceptual model. In practice it is OK that some implementations take liberties with the model by combining some of the layers or eliminating functionality that is not applicable to a specific implementation. The critical issue is that all the functionality is defined and, when necessary, is implemented. That is exactly what happens in the BACnet ecosystem.
The BACnet standard defines data objects, network objects, their properties, and services that operate on these objects. From this standpoint there is one BACnet. BACnet follows the spirit of the OSI model by allowing the implementor to choose from one of seven BACnet-defined transport methods. These transport methods are adopted from well-defined and standardized IT networking and cybersecurity technologies. Where necessary, BACnet specific network services are combined with these standard transport methods.
Using this approach, any “Thing” implemented by following the BACnet standard will successfully connect with and interoperate with other “Things” in the BACnet ecosystem. The BACnet Testing Laboratories function within BACnet International defines testing requirements and provides certification services to make sure that the above statement is true. BTL Certified products have passed the rigorous test procedures defined by the BTL Working Group. There are multiple testing laboratories around the world capable of providing testing services.
Here is a summary of the value proposition for “Things” that are built following the BACnet standard.
It is up to the product developer to provide the code in their “Thing” to implement the logic behind the BACnet protocol that delivers the unique services offered by their products. This leaves lots of room for innovation and competition between manufacturers. It is also up to the product developer to provide their own user interface and configuration and commissioning utilities consistent with the standards they have set for their brand.
The BACnet standard provides opportunities for both large building automation system (BAS) manufacturers and smaller, or niche, players. Nothing in the standard says that you need to offer every type of product defined by the BACnet profiles. If your product offering(s) follows the BACnet standard, it can participate in the BACnet ecosystem and either compete with, or augment, the products of larger players.
BACnet is at the heart of the Building IoT (BIoT) concept. Devices implemented following the BACnet standard provide local control critical to keeping buildings operational, maintaining Indoor Air Quality (IAQ) and occupant comfort, and energy efficiency to keep occupants safe and productive. Data from the local control environment can be sent to cloud-based systems where their value can complement, augment, and tune the local control provided by BACnet systems.
There are many application scenarios for BACnet and one of them is providing an integration platform for a building with a legacy BAS. To accomplish this, a specialized BACnet device can provide gateway/router services to/from the BACnet ecosystem. For example, the S4 Open: BACnet-N2 Router acts as the enabling technology to introduce BACnet-based “Things” to legacy buildings. It is a perfect example of using BACnet as the API which normalizes the data from legacy BAS implementations and allows them to fully participate in the BACnet ecosystem. All the code that provides the mapping between BACnet and the legacy systems, the user interface, the value-added features provided, and the legacy system protocol itself, is implementation specific and independent of the BACnet standard.
Similarly, each major BAS manufacturer typically offers a field level controller for Rooftop Unit (RTU) Controller applications. Every RTU talks to the BACnet ecosystem following the standard. But implementation details for all the algorithms beyond what is defined in the BACnet protocol are completely up to the manufacturer. They differentiate their products by the level of operational efficiency and the ease of use provided by their configuration and commissioning utilities.
BAS manufacturers also offer building level controllers and fully programmable devices. Like the above examples these devices communicate and interoperate with the BACnet ecosystem following the rules defined by the BACnet standard. It is beyond the scope of the BACnet standard to specify the functionality offered by these devices or the methodology offered by the manufacturer for the integrator to program these devices. There is lots of room here for manufacturers to differentiate themselves!
Operator Workstations and other display devices play another important role in the BACnet ecosystem. Again, they must follow the BACnet standard to be able to successfully connect and interoperate with the BACnet ecosystem. Here again, it is completely up to the developer to determine how they define their user interface and what value-added capabilities they offer beyond the functionality mandated by the standard. There is lots of room for innovation and differentiation of products while maintaining compliance with the standard.
These BACnet “Things” are Open Systems, Open Networks, Open Applications, or Open Devices depending on the application or service that they provide to the BACnet ecosystem.
We have not yet discussed Open Source. In fact, BACnet is represented in this area also. Many BAS manufacturers have implemented their own BACnet stacks following the BACnet standard. There are several commercial BACnet stack offerings that developers can include in their own products. There is also at least one Open-Source implementation of the BACnet stack where developers can utilize source code developed by others and contribute to its maintenance and enhancement for the benefit of the community. A variation of Open-Source is the reference implementation of BACnet Secure Connect (BACnet/SC) provided as part of BACnet International’s BACnet/SC Interoperability Acceleration Program.
BACnet adoption continues to grow because of the ongoing work of the BACnet Committee to enhance and extend its functionality as buildings evolve into Smart Buildings. The ongoing work of BACnet International, and BTL, to certify BACnet implementations, promote the use of BACnet, and provide educational and testing services makes sure that building owners, and their trusted advisors, understand that BACnet should be their first choice for automating their building systems.