BACnet stands for Building Automation and Control networks. BACnet is a data communication protocol developed by ASHRAE. Its purpose is to standardize communications between building automation devices from different manufacturers, allowing data to be shared and equipment to work together easily. BACnet is an international standard (ISO 16484-5), a European standard and a national standard in many countries.
There is a lot of information available about BACnet. One place to start for education and information is The BACnet Institute. The Institute includes an online, self-paced introductory BACnet course called BACnet Basics. It also has a curated, searchable library of white papers, conference presentations and videos on various BACnet-related topics. For answers to specific questions the Institute includes a Community Forum for discussion and knowledge-sharing. The BACnet Institute can be found at TheBACnetInstitute.com where the registration and content are free of charge.
BACnet reduces integration cost and risk while ensuring investments in building automation are preserved over time. It can interconnect multiple systems from diverse suppliers, enabling sophisticated energy management, occupant comfort, and building security applications. BACnet also simplifies building operation and maintenance by enabling integration of information and controls from all building systems into a single graphical interface. BACnet simplifies operations, reduces user training, streamlines maintenance, offers flexibility, and enables expansion, extension and cross-functional add-ons. That is why BACnet has grown to become the predominant worldwide building integration protocol.
If an owner becomes unhappy with product availability, service, replacement cost, or any other aspect of a specific vendor's installed BACnet compatible product, chances are there is a suitable replacement available from another company. The owner can be confident that matched BACnet products will perform in the system regardless of the manufacturer. Additionally, if a specific BACnet product is no longer manufactured, the owner may be able to substitute a device from an alternate manufacturer, rather than replacing the entire system or repairing old devices.
BACnet continues to make the industry more competitive, allows more choices, and provides capability for future expansion. It enables the property management company to minimize dependence on any single vendor, as well as allowing for the capability of remote monitoring. For smaller installations, this off-site service results in cost savings because the company can monitor many sites from one or more central property management locations. One operator interface can be used for many systems. Another potential benefit to a property management company is that it will be able to have a common operator interface across equipment from multiple vendors. This lowers staff training costs and reduces operator errors.
BACnet provides a standard, robust methodology for specifying the required networking capabilities of building automation solutions. This allows consulting engineers to clearly enumerate their requirements in a way that will provide a broad selection of suppliers and integrators. In addition, BACnet provides consulting engineers with some insurance against late-arriving system requirements since most devices that would need to be added can readily integrate with a BACnet solution. That is part of why BACnet has grown to become the predominant building automation integration protocol.
BACnet's inherent approach to communications had led to many BACnet devices being designed with extensive remote access capabilities. Web-based access to a building's BACnet control system from an engineer's office has become commonplace. This access to supervising BACnet installations translates into saved time and money for consultants responsible for monitoring installations.
A 2018 market study conducted by BSRIA titled "Market Penetration of Communications Protocols" indicated BACnet's global market share has continued to rise over the last five years and now exceeds 60%. The next most significant protocol has a market share of less than 15%. The five-year outlook projects continued growth in BACnet adoption with continual improvements to the standard.
Yes. BACnet gives you options to choose the right piece of equipment for the right job, from any manufacturer you want, instead of being limited to the brand of the system that's already in place. An increased set of choices permits finer tuning of the installation for better operation. For new installations and retrofits, BACnet offers a future of easy expansions and modifications. When carefully selected, new devices will interface easily with the BACnet system already in place. As a wider variety of BACnet devices have been developed, more comprehensive system integration of services such as access control, security, fire and life safety, and direct utility company cooperation has become commonplace.
Yes. System expansion was a major consideration in the development of BACnet. As a result, BACnet is very open-ended. It allows you to choose from a large range of devices. By selecting the right equipment, not only can a system be expanded, but it can also become more efficient. The building automation industry continuously develops and integrates new products into today's BACnet systems, while providing the means to accommodate tomorrow's needs.
Yes. There is an organization called the BACnet Testing Laboratories that defines and oversees testing and certifying of BACnet products. All BACnet products should be BTL tested to ensure a high level of interoperability. Users and specifiers should require BTL certification and/or listing for all products on their projects. The list of BTL tested and certified BACnet products is available on the BTL website along with information on the BACnet product testing process.
The BTL Listing is an online database of products that have successfully completed the industry accepted testing and certification process. Products that are not in the BTL product listing database have not been BTL tested or certified. Each product in the BTL product listing database has a BTL Listing document with information on the specific product model and version that was tested, along with its BACnet functionality.
A Certificate of Conformance is a formal document attesting to the fact that a product has successfully completed the BTL Certification process. BTL Certificates are a regulatory requirement in project submittals in some countries and regions.
All BACnet products that have completed the BTL Certification process have a certificate. However, some older products were BTL tested prior to completion of the Certification process and those products are in the BTL product listing database but might not have a certificate.
All BACnet devices share some capabilities that allow them to interoperate on a network with other BACnet devices. However, BACnet allows devices to implement only the parts of the standard that are needed to accomplish the function of the devices. This allows BACnet to be used in low-cost devices as well as high functionality devices. Also, BACnet only specifies how devices communicate and interoperate, the functionality of devices varies greatly by application and vendor.
PICS stands for "Protocol Implementation Conformance Statement." It is a document containing a list of a device’s BACnet capabilities. Every BACnet device is required to have one. It contains a general product description; details of a product's BACnet capabilities; which network options are available; and a few other items relating to character sets and special functionality. PICS are frequently used to get a first level understanding of a device’s BACnet capabilities. For more information, please visit the BACnet Committee's web page on Conformance PICS.
BACnet provides interoperability among control system components but does not directly impact how system data is presented to operators. So, knowledgeable building system operators are typically as comfortable with a BACnet system as any other system. Technicians typically utilize software tools to monitor, analyze and diagnose building automation networks. There are a variety of BACnet tools that operate across all supplier systems, resulting in skills portability for technicians and broader employee recruiting opportunities for building owner/operators.
BACnet offers a large set of options to meet the broad set of needs inherent in the building automation industry. However, like all control systems, BACnet systems require configuration, and in some cases application development work, to meet the functional requirements of a specific building system. Only for the simplest of operations would it be possible to just connect devices and have any meaningful result.
No. BACnet defines many kinds of interoperations between devices but it does not define a standard programming method. However, while programming tools are unique to each supplier, a variety of BACnet system diagnostic tools are available that allow technicians to analyze, optimize, operate, and diagnose BACnet devices, networks and configurations regardless of the equipment supplier. These tools allow technicians to readily support systems incorporating multiple brands of equipment.
BACnet is an open standard directed by the global community through several organizations that collaborate to support, extend and promote it. The standard itself is maintained and extended by an ASHRAE Standing Standards Project Committee (SSPC-135) operating according to international standards development rules. The selection of committee members represents a balance of vendors, end-users, consulting engineers, government, and interested third parties. In addition to SSPC-135, the BACnet community includes the BACnet Testing Laboratories (BTL) which handles global product certification, The BACnet Institute which is focused on BACnet education and information, as well as local, national, and regional user/supplier communities such as BACnet International, BACnet Interest Group Europe, and others.
All building sizes are suitable for BACnet building controls and automation solutions. BACnet supports simple systems with very few devices, and it also supports large, complex systems spanning multiple buildings. The BACnet standard is open-ended yet has stringent criteria for device interoperation. It is very comprehensive but does not require all devices to implement all capabilities. Thus, BACnet is robust enough for large, complex facilities, yet economically viable for small buildings.
BACnet provides explicit support for many building systems, including HVAC, Lighting, Access Control, Power Management,Elevators and others. BACnet also supports a broad set of general-purpose communications capabilities that can be applied to meet virtually any building control requirement. This has allowed BACnet to serve as an integration platform for all building control subsystems and a wide range of building-related systems including landscape sprinklers, parking lot lighting, EV charging stations and many, many others.
BACnet has been used in hundreds of thousands of installations around the world. Case studies can be found on the BACnet International website. European-specific case studies can be found in most issues of the BACnet Journal on the BIG-EU website. Another source for examples of BACnet implementation and case studies is in The BACnet Institute searchable resources database.
Yes. One of BACnet's major strengths is open-ended, multiple interfaces. Some BACnet devices allow existing non-BACnet systems to interface with BACnet devices. Once the proper interface has been selected, BACnet products may be matched, selected and used in conjunction with existing facility components.
Absolutely. Use of BACnet ensures controls installed today will be interoperable with controls installed in the future, whether they are from the same vendor or not. In addition, using BACnet in a single supplier installation preserves the future option of adding specialized equipment that is not available from the initial system supplier. Plus, the large pool of existing BACnet literate engineers and technicians creates staffing and service contract flexibility.
Yes. BACnet is an international standard (ISO-16848-5) as well as an ANSI standard which facilitates adoption by government and municipal entities. It allows them to specify interoperable equipment within the context of their normal procurement process. Many of the thousands and thousands of BACnet systems installed around the world are in government facilities.
A good BACnet specification will clearly state what kinds of functions involving multiple devices are required. For example, to manipulate a controller's schedule from a remote workstation, both the workstation and the controller must support the appropriate BACnet capabilities. Therefore, a good BACnet specification will comprehensively list required interactions across the network (such as time-based things, alarm and event requirements, and points that need to be shared between devices) and state that they must be accomplished using BACnet. A specification that just says "shall be BACnet" does not achieve very much because it is not sufficiently detailed.
To minimize cost and integration risks while ensuring future system expandability, all BACnet specifications should require the use of BTL Certified products.
As a rule, the specifier provides a detailed list of what information must be available through BACnet according to their perception of what is needed for each portion of a system. Left unspecified, the resulting system may or may not meet the needs of the user. In any particular case, it could be that unspecified information is readily available for future incorporation but not necessarily. This is one reason why it is important to specify the interoperable information correctly and fully up front.
Yes, BACnet supports IPv4 and IPv6 networks which provide for Ethernet, Wi-Fi, and other network technologies. In addition, BACnet supports a specific twisted pair networking technology (MS/TP) that is designed for building control applications.
Yes, internetworking has been designed into many BACnet products. Campus buildings on a site may be networked with existing or new LAN systems. Buildings not directly connected by LANs may be remotely monitored and controlled using Internet-enabled network routing equipment.
Not necessarily. Proprietary extensions can be designed to be interoperable with devices that include only standard BACnet capabilities. There are some specialized situations where this might be more effective or more efficient. However, the use of BACnet devices with proprietary extensions requires careful assessment to ensure it does not compromise basic interoperability or limit future system extension and enhancement possibilities.
There may be some advantages but also some drawbacks. A mixed system with both BACnet and other components will require more complex commissioning, maintenance, training and may lose some degree of interoperability. However, it might be the preferred solution in situations where there is already an installed base of functioning Modbus or KNX equipment that can be accessed from the BACnet network using an appropriate gateway device. It may also be the preferred solution in a new application where the required devices have KNX or Modbus but do not have an available BACnet interface.
The BACnet Institute includes a community forum where technical questions can be posted for review and responses by BACnet experts and the community at large. The forum maintains a searchable history of questions and responses that address many issues. The BACnet Institute also maintains a searchable library of white papers, presentations, and articles with a variety of technical and application-specific information.
The BACnet Committee website includes several resources that could be useful in answering technical questions. There are links to several product developer aids as well as instructions on signing up for the BACnet-L email list server where users can post questions for review and response by the BACnet product development community.
The BACnet standard specifies everything that is required to ensure devices can effectively interoperate across the network. This includes the physical interconnection, routing of messages, encoding of messages and the meaning of messages, including object and service definitions. BACnet has a broad set of capabilities and options to cost-effectively address complex, sophisticated devices and also address small, simple devices. The proper selection and interdependencies of various capabilities and options is also specified. Some things are specified directly, such as the encoding of bits to represent a value. Other things are specified by referring to other standards, such as IPv6.
Yes. BACnet supports IPv4 and IPv6 networks which provide for Ethernet, Wi-Fi and other network technologies. In addition, BACnet supports a specific twisted pair networking technology (MS/TP) that is designed for building control applications.
The BACnet standard specifies everything that is required to ensure devices can effectively interoperate across the network. This includes the physical interconnection, routing of messages, encoding of messages and the meaning of messages, including object and service definitions. Modbus defines message encoding and physical interconnection options but does not address the meaning of messages. So, unlike BACnet, using a Modbus device requires an integrator to know how that specific device represents information and then program a specific interface for it. This adds cost and long-term maintenance issues.
Ethernet is a standard for transporting messages from place to place across a network. This is necessary but not sufficient for ensuring building automation equipment can interoperate. In addition to transporting messages, it is necessary to ensure that both the sending and receiving equipment understand the content and context for each message. BACnet provides a standardized set of communications concepts and rules to ensure both pieces of equipment have the necessary understanding. BACnet is designed to serve as a cost-effective basis for a wide variety of building automation systems. To achieve that goal, BACnet supports different methods for transporting messages. Ethernet is one of the methods BACnet supports, but it is not the only one.
A BACnet router is a device that passes a message from one network to another without changing the form or content of the message. This kind of device is used to interconnect BACnet networks that have different media (Ethernet, MS/TP over twisted pair, etc.). It is a simple device that just routes BACnet messages where they need to go, without decoding or altering them. A BACnet gateway is a more complex device that is used to interconnect a BACnet network with a non-BACnet network (such as Modbus or KNX). A gateway must decode messages on each network and reformat or translate the information to meet the requirements of the other network to route messages where they need to go. Gateways generally require more configuration, commissioning and maintenance effort than a router, as well as being more costly.
BACnet gateways are not a preferred solution because they introduce additional configuration and system maintenance complexity as well as adding cost. In general, it is better to use devices and controllers that implement BACnet directly. However, when no device with the required capabilities is available with BACnet, then use of a gateway allows for that device to be integrated with the rest of the building system. In addition, where an existing network of devices is already in place (such as Modbus or KNX), use of a gateway to integrate those devices with the rest of the building system may be the most cost-effective and practical solution.