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A data communication protocol for
Building Automation and Control networks aims to provide you with basic information and knowledge on the BACnet protocol.

BACnet is the only protocol recognized as an international standard. BACnet allows intelligent systems from various industries and manufacturers to exchange information, such as temperatures, setpoints, schedules, trend logs and alarms, and coordinate equipment operation to achieve optimum building performance. It saves facility owners/managers the costs of purchasing, engineering and maintaining custom interfaces for supervising packaged HVAC equipment (e.g. chillers), as well as integrating diverse building systems such as HVAC, lighting, fire, elevators, electrical services, etc.

BACnet empowers facility owners/managers with the flexibility of expanding and adding systems without being locked into one manufacturer. Instead, they can select the most appealing technology and services available and gain investment protection because current systems can be expanded without replacing the entire system.

The BACnet standard is independent of specific hardware platforms and supports multiple LAN technologies, including the Internet. This allows BACnet to evolve unencumbered as new technologies develop according to public demand, unlike open protocols where the underlying hardware and LAN technologies are controlled by one or few commercial enterprises.

As an ANSI/ASHRAE standard controlled by an ASHRAE standards body, BACnet cannot be changed without public review. Users have a say in any changes that may affect the protocol. Conversely, proprietary or public (open) protocols can be changed at the discretion of the creator without the customer being made aware.

Contact Julian Kreho to schedule a BACnet® training or demonstration.

The information provided on this website comes from a variety of sources and no guarantee can be made to the accuracy, completeness or currency of the information provided or its fitness for any particular purpose. Please report any errors you my find.


  • What is BACnet®?
    BACnet® is a data communication protocol for Building Automation and Control networks. Developed under the auspices of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), its purpose is to standardize communication between building automation devices and systems from different manufacturers. The protocol is supported and maintained by ASHRAE Standing Standard Project Committee 135.
  • What are the benefits of BACnet?
    BACnet affords facility owners and managers maximum flexibility and cost-effectiveness by allowing control products made by different manufacturers to be integrated into a single, uniform system. It is designed to allow HVAC/R, lighting, fire, access and security devices to interoperate. Owners can select the best technologies and services available, with the investment protection of being able to competitively expand current systems, without being "locked in" or having to replace them in the event that an original supplier loses favor. BACnet also facilitates single workstation control in campus/multi-building environments composed of a variety of different manufacturer's control systems.
  • Why was BACnet developed?
    Before BACnet was developed, every manufacturer's control equipment line was based on its own proprietary protocol. Any time equipment from different manufacturers needed to share information, custom software and hardware had to be developed and maintain at considerable time and cost.
  • How was BACnet developed?
    BACnet was developed by a cross-section of industry professionals, comprising manufacturers, consulting engineers, end-users, government agencies and the academic community. It took over nine years to develop, was publicly reviewed and was adopted in 1995 as ANSI/ASHRAE Standard 135-1995.
  • Is BACnet an international standard?
    Yes. In addition to being an American national standard (ANSI), BACnet is an established European pre-standard (CEN) and in the final stages of becoming a world standard (ISO). There are now thousands of BACnet projects installed and operating across more than eighty countries worldwide.
  • What is interoperability?
    Interoperability is the result of different manufacturers' devices using a common set of rules for data structure and transmission, allowing them to exchange data and execute commands.
  • What installations are best suited for BACnet?
    BACnet can be implemented in any building or set of buildings, regardless of size. These systems can be very simple, with few devices, or very complex, with practically any number of devices and manufacturers.
  • Does BACnet apply to all system levels?
    Yes. From front-end workstations to network controllers and routers, central plant controllers, unitary controllers, actuators and sensors, BACnet is designed to be scaleable and provides a complete, cost-effective communication standard from top to bottom.
  • What networks does BACnet specify?
    BACnet specifies six network types to accommodate different project and system requirements. These networks use widely accepted LAN standards, including Ethernet (IEEE 802.3/ISO 8802-3), ARCNET (ANSI/ATA 878.1), master slave/token passing (MS/TP, a twisted-pair RS-485 network created by BACnet), point-to-point (PTP, also created by BACnet) and LonTalk. The sixth option, BACnet/IP, was added later on to allow BACnet messages to be transported across the Internet and other IP-based wide area networks.
  • What is native BACnet?
    Native BACnet typically refers to a device that inherently represents data in BACnet format and communicates utilizing BACnet messaging. Native BACnet devices can be connected to a BACnet system without requiring a gateway device or software driver to translate to and from any proprietary protocols. Typical examples of native BACnet devices would be a native BACnet VAV application controller at the field level, and a native BACnet general system controller for central mechanical systems (e.g. air handing units) at the automation level.
  • What are the advantages of native BACnet?
    Systems incorporating native BACnet devices at all levels provide facility owners and managers with superior system performance and interoperability. They are not compromised by proprietary software drivers and/or external gateways, which typically degrade system performance (throughput) and limit functional scope. Rather, BACnet messaging is utilized to communicate through all system levels, providing a consistent and seamless system-wide communications infrastructure. This also ensures owners with maximum investment protection and freedom of selection for future system expansion and upgrades, since they are not bound by the technical and commercial restrictions of proprietary drivers/gateways, as well as their potentially high maintenance costs.
  • When does a gateway make sense?
    It may be appropriate to specify an available gateway product for cost-effectively upgrading or expanding an existing facility with a BACnet system. The gateway bi-directionally translates the messages of the proprietary legacy system to and from the BACnet protocol, allowing them to interoperate. Another case is when integrating building systems that do not yet have native BACnet devices available (e.g. fire). Various gateways are available on the market for connecting proprietary equipment and systems to a BACnet system. Specifiers should carefully review the gateway performance specifications (including PICS) to verify that the system interoperability requirements can be met.
  • What is PICS?
    PICS stands for Protocol Implementation Conformance Statement. It is a detailed description for a given BACnet device stating its inherent BACnet capabilities. The level of BACnet functionality are typically scaled to suit the type of building automation device, ranging from simple intelligent peripheral devices to sophisticated operator workstations. Thus PIC statements are important for specifiers and users to ensure that the various devices will satisfy the desired interoperability requirements when designing and implementing integrated BACnet systems.
  • What are BIBB's?
    BIBB stands for BACnet Interoperability Building Block. BIBB's represent specific individual function blocks for data exchange between interoperable devices. They are designed to be a simplifying tool for engineers to be able to write concise specifications describing the interoperability requirements of the various devices comprising a BACnet system. The various BIBB's that have been defined to date are divided into five categories: data sharing; alarm & event management; scheduling; trending; device & network management.
  • How do I write a BACnet spec?
    A document published by the National Institute of Standards and Technology (NIST) - Internal Report 6392, GSA Guide to Specifying Interoperable Building Automation and Control Systems Using ANSI/ASHRAE Standard 135-1995, BACnet - may be particularly helpful. This report is available to the public at (located in the bibliography section).
  • What is the NIST BACnet Interoperability Testing Consortium?
    When BACnet was under public review, several commenters suggested that BACnet devices should actually be built and tested before releasing the standard. The committee agreed but needed to find a way to do the testing such that potential implementers could feel comfortable with the idea of bringing their prototypes together with those of their competitors for a non-competitive, non-judgmental evaluation. Also, they wanted to find a "neutral venue" for the testing, i.e., not one the vendors' manufacturing sites. Happily, NIST (National Institute of Standards and Technology) offered the use of its lab in Maryland. Moreover, NIST has a mechanism, known as a "Cooperative Research and Development Agreement," which allowed to set up the testing and still protect everyone's proprietary interests. There are currently 20 consortium members, 17 of whom are manufacturers.
  • What is BACnet International?
    BACnet International is an organization that encourages the successful use of BACnet in building automation and control systems through interoperability testing educational programs, and promotional activities. BACnet International complements the work of other BACnet-related groups whose charters limit their commercial activities.

    BACnet International members include companies involved in the design, manufacturing installation, commissioning, and maintenance of control equipment that uses BACnet for communication, as well as other interested persons.
  • What is the purpose of BACnet International?
    BACnet International's mandate is to encourage the successful and widespread use of BACnet in building automation and control systems through interoperability testing, educational programs, and promotional activities.
  • What is the BACnet Testing Laboratory (BTL)?
    The BACnet Testing Laboratories was formed by BACnet International to perform BACnet compliance & interoperability testing of building automation products utilizing BACnet. A product-listing program identifies the products tested by BTL that have passed the necessary requirements.
  • Why is BACnet compliance testing important?
    Compliance testing provides assurance of interoperability between different manufacturers' products by verifying that the products correctly implement BACnet.
  • Why specify products listed by BACnet International?
    Listed products are authorized to display the "BTL" logo, and are presented on BACnet International's web site. This enables specifying engineers and end users to specify and purchase listed products with the assurance that these products have passed extensive BACnet interoperability testing and comply with at least the mandatory BACnet standard.
  • Why is BACnet like tenage sex? Because...
    everyone talks about it,
    nobody really knows how to do it,
    everyone thinks everyone else is doing it,
    so everyone claims they are doing it...
For more information, contact The BACnet Guru.
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Julian Kreho

Julian Kreho An experienced IT and BACnet® consultant and an ASHRAE Associate Member, providing Information Technology, Networking, BACnet interoperability consulting, planning, design, implementation, commissioning, maintenance, troubleshooting and training to companies and individuals since 1993. Julian is passionate about high quality results, and offers significant hands-on experience in the field of BACnet Integration, Building Automation, Energy Management/Monitoring and Information Technology. (this website) is independently owned, operated and maintained by Julian Kreho to spread the word about, and in support of this fundamental and rapidly expanding network technology.

Contact Julian to get started with the BACnet protocol right away, or simply read through this website and it's links to learn at your own pace.