BACnet: Not Just a Vision Anymore

July 31, 2006
As an ever-evolving protocol that facilitates interoperability among building systems, BACnet now offers improved performance and integration

By Brady Nations

Momentum is clearly on the upswing as BACnet gains greater acceptance from engineers, contractors, and building owners. Manufacturers have stepped up their involvement as well. There are thousands of installations worldwide that use BACnet as a means for building systems to communicate with each other.

BACnet has been on the drawing board since June 1987, when a committee from the Atlanta-based American Society of Heating, Refrigerating, and Air-Conditioning Engineers Inc. (ASHRAE) met for the first time to develop a data-communication protocol covering the most common monitoring and control functions within a building. The central idea was to give building owners more freedom to choose from control-system suppliers and, with that freedom, a more competitive environment that would reduce installation costs.

With significant input from the industry’s major players, BACnet was published as an ASHRAE® standard in 1995. It has been continuously improved throughout the years by manufacturers, end-users, and other interested parties. Flexibility and expandability have been key design elements since the early planning stages. Today, nearly 2 decades later, the foresight of BACnet’s founding fathers is playing out in its proliferation. Quite simply, BACnet is here to stay.

Essentially, BACnet is a set of rules governing the exchange of data over a computer network to facilitate interoperability of various building systems. The five interoperability areas are:

  • Data sharing.
  • Alarm and event management.
  • Scheduling.
  • Trending.
  • Device and network management.

As a common communication language, BACnet makes it possible for systems from different manufacturers and/or systems designed for different building-automation and control functions to work together. BACnet equipment extends to controllers, gateways, routers, and diagnostic tools, and provides a means to send data to a workstation. The first BACnet objects to be defined involved the most common HVAC functions, followed by fire-alarm equipment in 2001. ASHRAE teams are working hard to extend BACnet’s advantages to important areas such as lighting, security, and utility integration.

Main Benefits for Building Owners
The benefits of interoperability within a BACnet-based facility are obvious. In theory, virtually any automated building control function can be monitored from a single-operator workstation, regardless of the control-system manufacturer and without the need for gateways that translate data between different systems. This simple, seamless interface levels the playing field between manufacturers and building owners, resulting in more competitive procurement of control systems.

This is a far cry from the 1980s, when the first direct digital control (DDC) systems were loaded with proprietary technology. In the beginning, there were no standard, off-the-shelf communication solutions, so controls manufacturers developed their own protocols. Building owners that wanted to add to a DDC system in their facility had to buy from the existing supplier and had no price leverage. “Vendor independence” meant adding a new vendor to the mix whose equipment did not talk to the original vendor’s equipment.

Empowering end-users through standardization was the primary motivator for ASHRAE to form a committee that led to BACnet’s creation. The standard is especially beneficial for large facilities and campus environments where building control and automation is extensive.

BACnet devices are limited in their effectiveness unless they can carry messages over a data network. There are a number of ways that BACnet allows this: Ethernet, Arcnet, LON®, MS/TP, and RS-232. The BACnet standard was amended in 1997 to include BACnet/IP. To date, BACnet/IP over Ethernet has been the most common choice of BACnet networking between systems from different vendors.

BACnet/IP allows devices to communicate directly with each other over the Internet or a corporate intranet. It also provides a method for BACnet devices to “sign up” to receive broadcast transmissions, even if they are not on a BACnet LAN. Web servers can be configured to receive information from BACnet networks and then present it in a format that can be viewed and/or altered from standard Web browsers.

Behind-the-Scenes Activities
The ASHRAE-sponsored BACnet committee is still very active, working on advancements to BACnet. But, BACnet would not be as well-established today if not for many behind-the-scenes efforts of dedicated groups from the building automation and control spectrum. These groups have clearly pushed BACnet into the forefront.

The BACnet Manufacturers Association (BMA) was a strong organization that encouraged the successful use of BACnet in building automation and control systems through interoperability testing, educational programs, and promotional activities. BMA members primarily included companies involved in the design, manufacture, installation, commissioning, and maintenance of control equipment that use BACnet for communication.

BACnet interest groups have sprung up across the world for the purpose of obtaining factual, impartial information on BACnet control systems. The mission of the BACnet Interest Group-North America (BIG-NA) is “to facilitate the open exchange of user ideas and experiences as the complete interoperability of building systems is achieved.” The group is composed of end-users, consultants, manufacturers, and other interested parties.

BMA and BIG-NA recently joined forces to create a new organization (called BACnet Intl.) that will more strongly advocate the value of open systems to the industry. Bringing these groups together also will help accelerate the development of tools and test processes to improve BACnet’s interoperability.

Another activity promoting BACnet’s benefits is the BACnet Conference and Expo, which is devoted to educating mechanical system-design professionals, integrators, and end-users on the benefits of the BACnet protocol. The ASHRAE-endorsed event includes seminars by industry leaders and a trade show that features multi-vendor interoperability demonstrations. Over the years, these conferences have been alternately organized by BIG-NA and BMA.

Greater industry awareness, along with publicity of the many successful BACnet installations, has made the protocol ever more appealing to the professionals who specify building automation control projects. A growing number of new installation projects in the United States now include the BACnet specification. With a uniform communication method, it’s easier to specify integrated systems. Once again, this is of enormous benefit to large facilities and campus environments.

Importance of Testing
A key factor in BACnet’s growth has been the improvement in BACnet products, which, in turn, has a great deal to do with testing.
Consulting engineers are reluctant to specify BACnet (and owners certainly do not want BACnet) if the products do not communicate as the standard intends they should. Therefore, manufacturers have been eager to test the interoperability of their BACnet components.

BACnet Intl. operates BACnet Testing Laboratories (BTL), a product testing and listing program for devices that have BACnet capability. BTL tests the BACnet functionality of a product to a set of requirements that are based on ASHRAE Standard 135.1P: Method of Test for Conformance to BACnet. Products that meet the BTL’s requirements are eligible to receive a BTL listing.

Another important testing forum is the BACnet Interoperability Workshop, commonly known as Plugfest. It is a BTL-sponsored event that has grown each year since 2000. Vendors convene to test their new products with BACnet devices from other vendors in a neutral, friendly environment. The legal terms of participation for Plugfest are as follows:

“The purpose of the workshop is to identify interoperability problems in BACnet products and the BACnet standard, and this requires an environment in which the participants feel comfortable discussing product functionality. Many participants will bring unreleased products, and other participants are expected to respect their privacy. All participants agree to keep confidential (for a period of 1 year) any information about other companies’ products obtained primarily as a result of their participation in the workshop. The BTL will collect information on interoperability problems identified during the workshop, and that information may be discussed among the participants in the BTL’s testing activities for purposes that are consistent with the charter of the BTL. All participants agree that the workshop is not a forum for discussions related to sales, marketing, business development, distribution, or any related matters.”

Looking back at the past six Plugfests, Jim Butler of Cimetrics has noticed a striking maturity of BACnet products. “In the early Plugfests, there were lots of problems getting products to communicate at even a basic level,” he says. “In the most recent Plugfests, those problems were very few. What we’re seeing is people focusing on the most complex features of BACnet, such as scheduling and trending, and getting their products to work.”

Continuous Enhancements
Part of BACnet’s appeal today includes the embellishments that have occurred ever since the ASHRAE standard was published in 1995. BACnet has simply refused to stand still. One of the turning points in its acceptability within the industry has been the concept of BACnet Interoperability Building Blocks (BIBBs) that was incorporated into the BACnet standard in 2001. Each BIBB states which BACnet feature must be implemented, from either the perspective of a client or a server, to achieve some communication result. It also created the idea of standard device profiles that specify collections of BIBBs that are appropriate for particular types of BACnet devices.

Let’s use temperature control in a room as an example: All of the details and variables that impact temperature control are now in a standard format. Integration is smoother and faster, and that adds up to cost savings for the end-user.

In May 2005, BACnet Testing Labs completed testing on the first group of BACnet Building Controllers. BACnet Building Controllers are typically used as supervisory controllers. They support standard BACnet objects and services that were designed for trending, event and alarm initiation, scheduling of actions, data sharing, and device management.

The device profile for BTL testing of BACnet Building Controllers requires that a device supports all of the BACnet Interoperability Building Blocks of the Advanced Application Controller profile, plus additional BIBBs such as trending and external-device scheduling, making BACnet Building Controllers the most advanced device profile tested to date.

Another exciting enhancement on the BACnet horizon is Web Services. An addendum to the BACnet standard that is currently out for public comment and review defines how BACnet will interact with applications outside of the building environment. Web Services is a set of tools and technologies that provides a common platform for integrating enterprise computing applications, such as financial, human resources, and other systems involved in running a business.

Consider the example of scheduling buildings in a university environment, where class schedules determine when building systems are required: Web Services can provide a path to have the academic scheduling system inform the building management system when buildings are needed, without human intervention. With a means to apply Web Services as part of the BACnet standard, important information such as energy consumption and equipment maintenance requirements will be available to systems that serve the unique needs of each building.

In a business climate where every piece of available information might be critical to the well-being of the enterprise, the availability of real-time data on energy consumption and equipment functionality is vital. As energy costs continue to rise, key indications of productivity - such as output per unit of energy - are becoming more common.

Emerging BACnet Applications
As noted earlier, the first series of BACnet products revolved around HVAC applications, followed by fire-alarm applications. ASHRAE Working Groups have been collaborating with other industries to extend BACnet’s presence throughout a building. These include the following:

  • Lighting Systems. The Lighting Applications Working Group is cooperating with both the National Electrical Manufacturers Association (NEMA) and the Illuminating Engineering Society of North America (IESNA) to support the requirements of lighting-control applications. These include dimming with various ramping and timing parameters, override situations, and integration with other building systems.
  • Security Systems. The Life Safety and Security Working Group has completed work on fire-alarm objects and is now focused on security-system requirements, including access control, intrusion detection, and CCTV.
  • Utilities Integration. The Utilities Integration Working Group is exploring communication methods that will tie building automation and control systems to public utility providers. This would help building owners with real-time price negotiation, reducing or shifting peak loads, and accessing data from utility meters.

Other ASHRAE Working Groups are exploring network security, Internet protocols, eXtensible Markup Language (XML), and other enhancements to the BACnet standard.

BACnet is Global
BACnet is not just an American phenomenon: It has steadily gained acceptance throughout the world.
Recent surveys reveal that BACnet installations are in nearly 100 countries and on every continent, including Antarctica (that’s because the inherent interoperability of BACnet and its many enhancements over the years have given end-users unprecedented freedom to mix and match building-control equipment from a growing array of manufacturers).

All recommended modifications to the ASHRAE standard are published openly and anyone can comment. Suggestions for improving BACnet come from professionals throughout the world. BACnet is truly living up to its original promise of making it easier to integrate building systems with diverse functions from different manufacturers. A global network of designers, manufacturers, installers, building owners, and operators are more frequently turning to BACnet as a way to make all the unique systems within a building perform as a more cohesive entity.

And, it is rapidly becoming an international standard that is supported by technical experts from around the world. BACnet has been approved as ISO Standard 16484-5, it is a Korean national standard, and is a European pre-standard. BACnet interest groups have formed in Europe, the Middle East, Australia, Asia, and Russia to market the protocol and resolve technical issues.

Brady Nations is regional sales manager at Milwaukee, WI-based Johnson Controls Inc. ( and a former member of the board of directors at the BACnet Manufacturers Association. This article was excerpted from the white paper under the same title, available on Johnson Controls’ website. (BACnet® is a trademark of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers Inc. ASHRAE® is a registered service mark of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers Inc. LON® is a registered trademark of Echelon Corp.)

Building Controls/Protocol Resources
A number of organizations’ websites offer insight into BACnet and other protocols and building-controls initiatives:

  • Air-Conditioning and Refrigeration Institute (ARI) at (
  • American Society of Heating, Refrigerating, and Air-Conditioning Engineers Inc. at
  • BACnet Interest Group - Europe at ( This site is not available in English.
  • BACnet Interest Group - Russia at ( English version is available on the site.
  • BACnet Intl. (formerly the BACnet Manufacturers Association and BACnet Interest Group - North America, which combined interests in Fall 2005) at (
  • BACnet: The Official Website of ASHRAE SSPC 135 (ASHRAE’s BACnet committee) at
  • Continental Automated Buildings Association (CABA) at (
  • Intl. Alliance for Interoperability North America (IAI-na), a global standards-setting organization (within the National Institute of Building Sciences) committed to promoting the exchange of information among all software platforms and applications serving the AEC and FM communities by adopting a single Building Information Model [BIM]), at
  • LonMark Intl. at (
  • Organization for the Advancement of Structured Information Standards, the standards development consortium serving as the governing body for the oBIX - Open Building Information Xchange - protocol, at (

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