The experiences of users and implementers of BACnet have led to many constructive suggestions for improving the original standard, ANSI/ASHRAE 135-1995 and, more recently, to its successors, ANSI/ASHRAE 135-2001, 135-2004 and 135-2008. The files available below are in Adobe Portable Document Format (PDF). Anyone wishing to comment on public review drafts during the listed comment period can get the necessary forms and instructions on the ASHRAE Website.

This Page was Last Updated on December 3, 2009

BACnet Protocol Version and Revision Numbers

With the publication of Addenda 135-2008j, l, o, r, s, v on June 20, 2009, the following apply:

Note: Many of the addenda to BACnet-2008 were begun during the "lifetime" of BACnet-2004 but their development and final public reviews were not completed in time to be incorporated into BACnet-2008. Therefore, some of the files for earlier drafts contain the string "2004" in their titles even though they pertain to revisions to BACnet that will eventually be applied to BACnet-2008 or, possibly, subsequent consolidated versions of the standard.

• Addendum 135-2008g (This addendum completed its 4th Public Review on May 4, 2009 and comment processing is complete. No substantive changes are anticipated so the addendum is now awaiting publication.
   
1. Updating BACnet Network Security

Here is the link to the First Public Review Draft of Addendum 135-2008g.
Here is the link to the Second Public Review Draft of Addendum 135-2008g.
Here is the link to the Third Public Review Draft of Addendum 135-2008g.

• Addendum 135-2008h (This addendum completed its 4th Public Review on May 4, 2009. All comments were resolved and the addendum is now awaiting publication.)
   
1. Change Device_Busy to Busy and apply to the Command Object type
2. Prevent overflow and underflow in Pulse_Converter object's Count property
3. Add context tags to Clause 21 production BACnetPropertyStates
4. Add new BACnetEngineering Units
5. Define COV notification service Error returns
6. Remove non-support for automatic cancellation of COV subscriptions
7. Add support for the UTF-8 character set
8. Add even and odd day support in scheduling

Here is the link to the First Public Review Draft of Addendum 135-2008h.
Here is the link to the Second Public Review Draft of Addendum 135-2008h.
Here is the link to the Third Public Review Draft of Addendum 135-2008h.

• Addendum 135-2008i (This addendum completed its 3rd Public Review on May 4, 2009. Substantive changes have been made so the addendum is awaiting a 4th public review.)
   
1. Define new Lighting Output object type
2. Add support for breaker-tripped status to Analog and Binary Output objects
3. Add warning-blink support to Binary Output and Binary Value objects

Here is the link to the First Public Review Draft of Addendum 135-2008i.
Here is the link to the Second Public Review Draft of Addendum 135-2008i.

• Addendum 135-2008j (This addendum is final and was approved by the ASHRAE Standards Committee on June 20, 2009; by the ASHRAE Board of Directors on June 24, 2009; and by the American National Standards Institute on June 25, 2009.) The addendum defines physical access control extensions to BACnet. Although access control is part of the building automation system, in many ways it is more complex and has different constraints and requirements than typical HVAC control. In particular, there is a much greater emphasis on the security of the devices and the communications to those devices. Addendum 135-2004g provides a new BACnet security architecture to address these and other concerns.)
   
1. Add a new Access Point object type
2. Add a new Access Zone object type
3. Add a new Access User object type
4. Add a new Access Rights object type
5. Add a new Access Credential object type
6. Add a new Credential Data Input object type
7. Add a new Access ACCESS_EVENT event algorithm
8. Add a new Annex P BACnet encoding rules for authentication factor values


• Addendum 135-2008k (This addendum completed its 2nd Public Review on May 4, 2009. All comments were resolved and the addendum is now awaiting publication.) Addendum 135-2008k adds support for one "Character Encoding Form" at a time, needed for interoperability. Also incorporates the Japanese Industrial Standard Committee's change from "JIS C 6226" to "JIS X 0208."
   
1. Add support for one Character Encoding Form at a time

Here is the link to the First Public Review Draft of Addendum 135-2008k.

• Addendum 135-2008l (This addendum is final and was approved by the ASHRAE Standards Committee on June 20, 2009; by the ASHRAE Board of Directors on June 24, 2009; and by the American National Standards Institute on June 25, 2009.) Addendum 135-2008l adds new operator workstation profiles and BIBBs.
   
1. Add new workstation BIBBs and profiles

Here is the link to the First Public Review Draft of Addendum 135-2004l.
Here is the link to the Second Public Review Draft of Addendum 135-2008l.
Here is the link to the Third Public Review Draft of Addendum 135-2008l.

• Addendum 135-2008n (This addendum completed its 3rd Public Review on May 4, 2009. All comments were resolved and the addendum is now awaiting publication.)
   
1. Add support for long Backup and Restore preparation times

Here is the link to the First Public Review Draft of Addendum 135-2008n.
Here is the link to the Second Public Review Draft of Addendum 135-2008n.

• Addendum 135-2008o (This addendum is final and was approved by the ASHRAE Standards Committee on June 20, 2009; by the ASHRAE Board of Directors on June 24, 2009; and by the American National Standards Institute on June 25, 2009.)
   
1. Accommodate remote operator access and NAT in Annex J BACnet/IP


• Addendum 135-2008p (This addendum is now undergoing a 45-day 2nd Public Review from September 11 to October 26, 2009.)
   
1. Add a new Global Group object type

Here is the link to the First Public Review Draft of Addendum 135-2008p.

• Addendum 135-2008q (This addendum is final and was approved by the ASHRAE Standards Committee on January 24, 2009; by the ASHRAE Board of Directors on January 28, 2009; and by the American National Standards Institute on January 29, 2009.)
   
1. Allow unicast I-Ams
2. Define virtual addressing for data links with MAC addresses longer than 6 octets
3. Define the use of ZigBee as a BACnet data link layer


• Addendum 135-2008r (This addendum is final and was approved by the ASHRAE Standards Committee on June 20, 2009; by the ASHRAE Board of Directors on June 24, 2009; and by the American National Standards Institute on June 25, 2009.)
   
1. Clarify transitions in FLOATING_LIMIT and OUT_OF_RANGE events
2. Clarify router action when a network is marked as temporarily unreachable
3. Clarify the destination MAC used when replying to a broadcast DER frame
4. Clarify the handling of write priorities greater than 16
5. Clarify LogDatum presentation


• Addendum 135-2008s (This addendum is final and was approved by the ASHRAE Standards Committee on June 20, 2009; by the ASHRAE Board of Directors on June 24, 2009; and by the American National Standards Institute on June 25, 2009.)
   
1. Clarify the circumstances that cause the File object's Archive property to be set to TRUE or FALSE
2. Require support for COV subscriptions of at least 8 hours' lifetime
 

• Addendum 135-2008t (This addendum is now undergoing a 45-day 3rd Public Review from September 11 to October 26, 2009.) Link is to a ZIP file containing the draft, 4 supplementary files and a "README" file. A new standard way of representing building data will give BACnet new capabilities for standardized communications between a wide range of applications. A definition for an XML syntax which can be used to represent building data in a consistent, flexible and extensible manner is defined by this addenda in the form of a new annex to the standard.

  The Extensible Markup Language (XML) is a popular technology in the data processing and communications worlds due to its ability to model a wide range of data and its ability to be transformed and extended. With this new IT-friendly way of representing building data, BACnet will open up a range of possible new ways to share data. XML can be used for exchanging files between systems, integrating buildings with energy utilities, and expanding enterprise integration with richer Web services. Some of these new applications will be standardized in future addenda to the standard based on the syntax defined here.

1. XML Data Formats

Here is the link to the First Public Review Draft of Addendum 135-2008t and its related documents.
Here is the link to the Second Public Review Draft of Addendum 135-2008t and its related documents.

• Addendum 135-2008u (This addendum is now undergoing a 45-day 2nd Public Review from September 11 to October 26, 2009.)
   
1. Clarify the use of RejectPDUs
2. Add error code UNSUPPORTED_OBJECT_TYPE for CreateObject service
3. Add new Abort and Error codes
4. Specify proper Errors when attempting access to the Log_Buffer property

Here is the link to the First Public Review Draft of Addendum 135-2008u.

• Addendum 135-2008v (This addendum is final and was approved by the ASHRAE Standards Committee on June 20, 2009; by the ASHRAE Board of Directors on June 24, 2009; and by the American National Standards Institute on June 25, 2009.)
   
1. Fix the MS/TP TokenCount Value
2. Clarify "Supported"
3. Remove NM-CE-A from Device Profiles


• Addendum 135-2008w (This addendum is now undergoing a 45-day 2nd Public Review from September 11 to October 26, 2009.)
   
1. Add more primitive value objects
2. Add reference times for scheduling

Here is the link to the First Public Review Draft of Addendum 135-2008w.

• Addendum 135-2008x (This addendum is now undergoing a 45-day 1st Public Review from September 11 to October 26, 2009.)
   
1. Fix the Criteria for COV for Load Control
2. Clarify Trend Log Time Stamp
3. Clarify ReadRange on Lists
4. Clarify Results of Using Special Property Identifiers


• Addendum 135-2008y (This addendum is now undergoing a 45-day 1st Public Review from September 11 to October 26, 2009.)
   
1. Specify Deployment Options for MS/TP


• Addendum 135-2008z (This addendum is now undergoing a 45-day 1st Public Review from September 11 to October 26, 2009.)
   
1. Add Event_Message_Texts
2. Add UnconfirmedEventNotification to Automated Trend Retrieval BIBBs
3. Modify MS/TP State Machine to Ignore Data Not For Us
4. Add New Engineering Units
5. Add Duplicate Segment Detection

• Addendum 135-2004a (This addendum was approved for publication by the ASHRAE Board of Directors and by the American National Standards Institute on February 10, 2005.)
   
1. Revise Life Safety Point and Life Safety Zone objects to modify their behavior when placed out of service
 

• Addendum 135-2004b (This addendum was approved by ASHRAE Board of Directors on October 24, 2008 and by the American National Standards Institute on October 27, 2008.)
   
1. Add a new Event Log object type
2. Add a new Global Group object type
3. Add a new Trend Log Multiple object type
4. Harmonize the Trend Log object with the new Event Log and Trend Log Multiple objects
5. Define a means for a device to provide a notification that it has restarted
6. Define a means to configure a device to periodically send time synchronization messages
7. Extend the number of character sets supported
8. Enable devices other than alarm recipients to acknowledge alarms
9. Allow MS/TP BACnet Data Expecting Reply frames to be broadcast
10. Revise the Clause 5 state machines to handle slow servers
11. Add new Error Codes and specify usage
12. Add new Reliability enumeration to objects with a Reliability property

Here is the link to the First Public Review Draft of Addendum 135-2004b.
Here is the link to the Second Public Review Draft of Addendum 135-2004b that contains contains only independent substantive changes made to the first public review draft and must be reviewed with that document.
Here is the link to the Third Public Review Draft of Addendum 135-2004b that contains contains only independent substantive changes made to the second public review draft and must be reviewed with that document.

• Addendum 135-2004c (This addendum was approved for publication by the ASHRAE Board of Directors September 29, 2006 and by the American National Standards Institute on October 2, 2006.)
   
1. Add BACnet/WS web services interface


• Addendum 135-2004d (This addendum was approved for publication by the ASHRAE Board of Directors June 29, 2006 and by the American National Standards Institute on June 30, 2006.)
   
1. Add a new Structured View object type
2. Allow acknowledgement of unseen TO-OFFNORMAL event notifications
3. Relax the Private Transfer and Text Message BIBB requirements
4. Exclude LIFE_SAFETY and BUFFER_READY notifications from the Alarm Notifications BIBBs
5. Establish the minimum requirements for a BACnet device with an application layer
6. Remove the requirement for the DM-DOB-A BIBB from the B-OWS and B-BC device profiles
7. Relax mandated values for APDU timeouts and retries when configurable, and change default values
8. Fix EventCount handling error in MS/TP Master Node State Machine
9. Permit routers to use a local network number in Device_Address_Binding
10. Identify conditionally writable properties
11. Specify Error returns for the AcknowledgeAlarm service


• Addendum 135-2004e (This addendum was approved for publication by the ASHRAE Board of Directors March 25, 2007 and by the American National Standards Institute on March 26, 2007.)
   
1. Add a new Load Control object type
 
Here is the link to the First Public Review Draft of Addendum 135-2004e.
Here is the link to the Second Public Review Draft of Addendum 135-2004e that contains only independent substantive changes made to the first public review draft and must be reviewed with that document.
 

• Addendum 135-2004f (This addendum was approved for publication by the ASHRAE Board of Directors March 25, 2007 and by the American National Standards Institute on March 26, 2007.)
   
1. Add a new Access Door object type

Here is the link to the First Public Review Draft of Addendum 135-2004f.
Here is the link to the Second Public Review Draft of Addendum 135-2004f.

• Addendum 135-2004m (This addendum was approved for publication by the ASHRAE Board of Directors on October 24, 2008; and by the American National Standards Institute on October 27, 2008.) Addendum 135-2004m contains 12 independent changes to the BACnet standard, including: resolving Foreign Device registration period ambiguities, clarifying the GetEventEnrollment service's Priority Filter parameter, adding requirements to Alarm and Event BIBBs, and defining "object."
   
1. Resolve Foreign Device registration grace period and remaining time ambiguities
2. Improve Clause 5 FillWindow segment timeout constraints
3. Clarify the Priority Filter parameter in the GetEventEnrollment service request
4. Allow alarms to be re-acknowledged successfully
5. Add requirements to Alarm and Event BIBBs
6. Remove B-BC requirements for BIBBs without use cases
7. Clarify that a device may support only the ReinitializeDevice restart choices
8. Clarify DeviceCommunicationsControl and ReinitializeDevice interactions
9. Define "object"
10. Add a Deadband property to the Loop object
11. Correct the TO-FAULT conditions in the Life Safety objects' Reliability properties
12. Clarify the Trend Log's acquisition of Status_Flags

Here is the link to the First Public Review Draft of Addendum 135-2004m.

 

• Addendum 135-2001a
  1. Add Partial Day Scheduling to the Schedule object
  2. Enable reporting of proprietary events by the Event Enrollment object
  3. Allow detailed error reporting when all ReadPropertyMultiple accesses fail
  4. Remove the Recipient property from the Event Enrollment object
  5. Add the capability to issue I-Am responses on behalf of MS/TP slave devices
  6. Add a new silenced mode to the DeviceCommunicationControl service
  7. Add 21 new engineering units
  8. Specify the behavior of a BACnetArray when its size is changed
  9. Clarify the behavior of a BACnet router when it receives an unknown network message type
   
  
• Addendum 135-2001b
  1. Remove UTC timestamps from Trend Logs and guarantee Trend Log record ordering
   
  
• Addendum 135-2001c
  1. Allow Life Safety objects to advertise supported mode
  2. Add Unsilence Options to the LifeSafetyOperation Service
  3. Specify the relationship between the Event_Type and Event_Parameter properties
  4. Add a new Accumulator Object Type
  5. Add a new Pulse Converter Object Type
  6. Standardize event notification priorities
  7. Define Abort reason when insufficient segments are available
  8. Add new Error Codes and specify usage
   
  
• Addendum 135-2001d
  1. Add clauses describing BACnet-EIB/KNX mapping

• Addendum 135-1995a
  1. Add Annex J - BACnet/IP and supporting definitions
   
  
• Addendum 135-1995b
  1. Inconsistencies are eliminated in the definitions of the Analog and Binary Value object types
  2. Any device that receives and executes UnconfirmedEventNotification service requests must support programmable process identifiers
  3. Modify each event-generating object type to contain the last timestamp for each acknowledgeable transition
  4. Modify the Notification Class object by requiring that the 'Notification Class' property be equivalent to the instance number of the Notification Class object
  5. Modify the Event Notification services to make the 'To State' parameter mandatory for notifications of type ACK_NOTIFICATION
  6. A new BACnetDeviceObjectPropertyReference production is added and its use in the Event Enrollment and Schedule object types is specified
  7. Add a Multi-state Value object type
  8. Add an Averaging object type
  9. Change all 'Process Identifier' properties and parameters to Unsigned32
  10. Change the Multi-state Input object type to correct flaws related to fault detection and reporting and achieve consistency with the proposed Multi-state Value object type
  11. Add a Protocol_Revision property to the Device object type
  12. The File object type is changed to allow truncation and partial deletion operations
  13. A new ReadRange service is added to permit reading a range of data items from a property whose datatype is a list or array of lists
  14. A new UTCTimeSynchronization service is introduced and related changes are made to properties in the Device object type
  15. Add a Trend Log object type
  16. The UnconfirmedCOVNotification service is extended to allow notifications without prior subscription as a means of distributing globally important data to a potentially large number of recipients
  17. Add eight new BACnet engineering units
   
  
• Addendum 135-1995c
  1. Add a new Life Safety Point object type that represents the characteristics of initiating and indicating devices in the fire, life safety, and security applications
  2. Add a new Life Safety Zone object type that represents the characteristics associated with an arbitrary group of BACnet Life Safety Point and Life Safety Zone objects
  3. Add functionality to the existing BACnet alarm and event features needed to support the Life Safety Point and Life Safety Zone object types
  4. Add a new LifeSafetyOperation service that provides silence and reset capabilities needed for life safety systems
  5. Add a new subclause to 19 to describe the use of existing BACnet services to provide backup and restore capability
  6. Define a new service, SubscribeCOVProperty, to allow COV notifications for arbitrary properties of an object with subscriber-specified COV increments
  7. Add Vendor ID to proprietary MS/TP frames
  8. Add a new service, GetEventInformation, that provides enough information to acknowledge alarms
   
  
• Addendum 135-1995d
  1. Replace Clause 22 with a new clause entitled "Conformance and Interoperability"
  2. Update Annex A, "Protocol Implementation Conformance Statement"
  3. Add a new Annex K entitled "BACnet Interoperability Building Blocks (BIBBs)"
  4. Add a new Annex L entitled "Descriptions and Profiles of Standardized BACnet Devices"
   
  
• Addendum 135-1995e
  1. Define the PTP connection status when the half-router can and cannot re-establish the connection
  2. Add Object Profiles and Extensions
  3. Add the capability for devices to advertise the maximum number of segments of a segmented APDU that they can receive

The need to define a set of procedures for the testing of BACnet implementations has led to the drafting of a companion standard, ANSI/ASHRAE 135.1, Method of Test for Conformance to BACnet. The companion standard to ANSI/ASHRAE Standard 135 (BACnet) contains detailed tests for every feature of the BACnet protocol and provides the basis for testing and listing programs that have been established by BACnet International, the successor organization to the BACnet Manufacturers Association.

• Addendum 135.1-2007b (This addendum is final and was approved by the ASHRAE Standards Committee on June 20, 2009; by the ASHRAE Board of Directors on June 24, 2009; and by the American National Standards Institute on June 25, 2009.)
1. Omit certain tests when Averaging and Command properties are fixed or not present
2. Accommodate Group objects whose members list is not changeable
3. Revise Alarm Acknowledgement tests
4. Add new Alarm Acknowledgement "offnormal" tests
5. Label conditionally-writable properties in the EPICS
6. Add new object types
• Addendum 135.1-2007d (This addendum is now undergoing a 45-day 2nd Public Review from September 11 to October 26, 2009.)
1. Add test to verify that COV subscription lifetimes are not affected by time-sync requests
2. Add new Active_COV_Subscription tests

Here is the link to the First Public Review Draft of Addendum 135.1-2007d.

• Addendum 135.1-2007e (This addendum completed its 1st Public Review on May 4, 2009. The committee is continuing to draft changes.)
1. Revise BACnet/IP tests

• Addendum 135.1-2003a (This addendum was approved by the ASHRAE Standards Committee on January 21, 2006; by the ASHRAE Board of Directors on January 26, 2006; and by the American National Standards Institute on January 27, 2006.)
   
1. Add Partial Day Scheduling to the Schedule object
2. Enable reporting of proprietary events by the Event Enrollment object
3. Allow detailed error reporting when all ReadPropertyMultiple accesses fail
4. Remove the Recipient property from the Event Enrollment object
5. MS/TP slave proxy tests
6. Add a new silenced mode to the DeviceCommunicationControl service
7. Addition of tests for Data Sharing BIBBs
8. Specify the behavior of a BACnetARRAY when its size is changed
9. Clarifying the behavior of a BACnet router when it receives an unknown network message type
10. Testing unsupported service request execution
11. Reading entire arrays
12. Update negative tests
 

• Addendum 135.1-2003c (This addendum was approved by the ASHRAE Standards Committee on June 23, 2007; by the ASHRAE Board of Directors on June 27, 2007; and by the American National Standards Institute on June 28, 2007.)
   
1. Update references to refer to 135-2004
2. Add new object types from 135-2004
3. Omit certain tests based on Protocol_Revision
4. Exception schedule priority requirements
5. Minor corrections