Still 'Bullish on BACnet'

Almost three years ago, Consulting-Specifying Engineer published “Bullish on BACnet,” an article by then editor Jim Crockett, to update its readers on advances in ANSI/ASHRAE Standard 135-2004, “BACnet—A Data Communication Protocol for Building Automation and Control Networks.


Almost three years ago, Consulting-Specifying Engineer published “Bullish on BACnet,” an article by then editor Jim Crockett, to update its readers on advances in ANSI/ASHRAE Standard 135-2004, “BACnet—A Data Communication Protocol for Building Automation and Control Networks.” Those were exciting times for BACnet, with its adoption around the globe, and its commitment to evolving with building and information technologies.

Since then, BACnet has not only made good on that commitment, but the scope and pace at which it is doing so are increasing. Since 2005, BACnet has extended into more areas of building automation, added new features and capabilities, and expanded into international markets.

Going into 2008, BACnet is poised to make substantial additions to its extensions through the next round of proposed addenda to the standard. This article provides a look at these addenda, and a synopsis of BACnet's direction beyond 2008.

The addenda agenda

At the 2008 ASHRAE Winter Meeting in January, the BACnet Committee will vote on key addenda that will submit for public review shortly afterward. Some of these addenda were in public review in the spring and fall of 2007, and comments from those reviews are being incorporated for this next round of public reviews. In addition, several new addenda are being prepared for their first public review. All told, the Committee is readying 13 addenda for public review starting on March 21, most for 45-day reviews.

Among the proposed addenda to BACnet are the following:

  • Addendum g : Secure communications on all BACnet networks

  • Addendum i : Extensions to support lighting controls

  • Addendum j : Extensions to support physical access control

  • Addendum l : Specify different kinds of BACnet workstations

  • Addendum o : BACnet/IP and NAT firewalls

  • Addendum p : New capability needed by the Japanese market

  • Addendum q : BACnet/ZigBee wireless

Of these, Addenda, g , i , j , l , o and q are of particular interest to the engineering community, so more information about them is provided below.

The goal of Addendum g is to secure network communications on all BACnet networks, using encryption and authentication. Because the original security mechanisms in BACnet, based on the old Data Encryption Standard (DES), have been rendered insecure by advances in computer technology, the BACnet Network Security Working Group has developed replacement mechanisms based on the newer Advanced Encryption Standard (AES) adopted by the U.S. government. An added benefit of AES is that it is simple enough that all BACnet networks can be secured, which would have been difficult and expensive with the computation-heavy DES.

Addendum i presents extensions to support lighting control in BACnet directly, as well as to support gateways to DALI lighting systems. The BACnet Lighting Applications Working Group is working with IESNA (the Illumination Engineering Society of North America) to develop these extensions, which will provide direct support for lighting controllers from simple on/off controllers up to complex controllers with continuous analog-lighting level control, ramping at fixed rates of change, fading over a fixed period of time, and incrementally stepping values up and down.

Addendum j will complete BACnet's support of physical access control, building on the Access Door object published in 2007. Representatives of several access control manufacturers are participating in the BACnet Life Safety and Security Working Group, as well as mutual liaisons with the Security Industry Assn., to ensure that the security industry's state-of-the-art practices are being incorporated. As with Addendum i, these extensions use the existing BACnet communications platform, which allows these new capabilities to be retrofitted in buildings already using BACnet.

Addendum l introduces a means for specifying different kinds of BACnet workstations, from simple wall-mounted LCD devices or hand-held terminals up to advanced workstations able to monitor system performance and modify system parameters. In addition it includes a new life-safety workstation specially intended to support BACnet's life-safety capabilities.

Addendum o was drafted by the BACnet Internet Protocol Working Group to deal with issues arising from the increased use network address translation (NAT) firewalls since BACnet's Internet Protocol (BACnet over IP) capability was first developed. For example, NAT firewalls generally allow connections to be established only between devices inside and outside the firewall if the connection originates from the device inside the firewall, which makes access to the system from workstations outside the firewall difficult.

Addendum q defines a new BACnet/ZigBee wireless capability. The BACnet Wireless Networking Working Group and the ZigBee community have been working together to marry the two technologies, the goal being to give BACnet a short-range wireless LAN for use in installations where a wired LAN is either too expensive or impossible.

BACnet in demand

The BACnet Utilities Integration Working Group (UI-WG) has been working with the energy utilities and their industry organizations to develop automated communications between the utilities and buildings to automate the exchange of information about real-time energy pricing and needs for temporary demand reduction. Such communications aid strategies for reducing energy costs, as well as reducing more expensive brownouts or blackouts.

In an example of how one BACnet extension can facilitate another, the UI-WG has proposed to convey these communications between the buildings and utilities using the BACnet Web Services development discussed in 2005's “Bullish on BACnet.”

BACnet “going up”

In 2007, BACnet “elevated” its coverage of areas of building automation even more with its response to a request from the elevator industry to integrate elevator monitoring into BACnet. A jointly developed technical proposal to add elevator support to BACnet has been submitted to the BACnet Objects and Services Working Group.

Internationally speaking

When “Bullish” was published, BACnet had been an ISO standard for almost a year and a half. As an ISO standard, its international support has grown. In addition to the four regional BACnet interest groups around the world at the time (Europe, North America, AustralAsia and the Middle East), new national groups in Russia, Sweden, Finland and France have been formed, with more announcements forthcoming.

Even BACnet conformance testing has gone international. The original North American BACnet Testing Lab, which certifies equipment for BACnet compliance, is now operated in India by BACnet International. A second lab is now open in Germany, operated by the BACnet Interest Group—Europe.

Still bullish

As exciting as things were for BACnet when “Bullish on BACnet” was published in 2005, it was hard to imagine that three years later it would so much more so today. With the advancement of BACnet into new areas of building automation, the development of more capabilities in BACnet, and the increasing support of BACnet internationally, it's easy to still be bullish on BACnet.

Author Information

Bill Swan is ECC Buildings Standards Initiatives Leader at Alerton/Honeywell, Redmond, Wash., and chair of the ASHRAE BACnet committee.


The Web site for the BACnet committee is

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. Its Web site address is

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