oSIST prEN ISO 16484-5:2026

Building automation and control systems (BACS) - Part 5: Data communication protocol (ISO/DIS 16484-5:2026)

The purpose of this document is to define data communication services and protocols for computer equipment used for monitoring and control of HVAC&R and other building systems and to define, in addition, an abstract, object-oriented representation of information communicated between such equipment, thereby facilitating the application and use of digital control technology in buildings.

Systeme der Gebäudeautomation - Teil 5: Datenkommunikationsprotokoll (ISO/DIS 16484-5:2026)

Systèmes de contrôle et d'automatisation des bâtiments (BACS) - Partie 5: Protocole de communication de données (ISO/DIS 16484-5:2026)

L'objectif de cette norme est de définir des services et des protocoles de communication de données pour les équipements informatiques utilisés pour la surveillance et le contrôle des systèmes CVC&R et d'autres systèmes de bâtiment et de définir, en outre, une représentation abstraite et orientée objet des informations communiquées entre ces équipements, facilitant ainsi l'application et l'utilisation de la technologie de contrôle numérique dans les bâtiments.

Sistemi za avtomatizacijo in regulacijo stavb - 5. del: Protokol za izmenjavo podatkov (ISO/DIS 16484-5:2026)

Namen tega dokumenta je opredeliti storitve in protokole za prenos podatkov za računalniško opremo, ki se uporablja za nadzor in upravljanje HVAC&R (ogrevanje, prezračevanje, klimatizacija in hlajenje) ter drugih sistemov v stavbah, ter dodatno opredeliti abstraktno, objektno usmerjeno predstavitev informacij, ki se izmenjujejo med takšno opremo, s čimer se olajša uporaba in uporaba digitalne krmilne tehnologije v stavbah.

General Information

• Status: Not Published
• Public Enquiry End Date: 24-Jun-2026
• ICS: 35.240.67 - IT applications in building and construction industry
• ICS: 97.120 - Automatic controls for household use
• Technical Committee: OGS - Heating for buildings
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 09-Apr-2026
• Due Date: 27-Aug-2026
• Ref Project: prEN ISO 16484-5 - Building automation and control systems (BACS) - Part 5: Data communication protocol (ISO/DIS 16484-5:2026)

Relations

• Revises: SIST EN ISO 16484-5:2022 - Building automation and control systems (BACS) - Part 5: Data communication protocol (ISO 16484-5:2022)
• Effective Date: 01-Jun-2026

Overview

oSIST prEN ISO 16484-5:2026, part of the ISO 16484 series, specifies the data communication protocol for Building Automation and Control Systems (BACS). Developed by CEN and ISO/TC 205, this standard defines key communication mechanisms that support effective integration, monitoring, and control of HVAC&R and other building systems using digital technology. By outlining both communication services and an object-oriented information model, oSIST prEN ISO 16484-5:2026 facilitates interoperability and reliable data exchange in complex building environments.

Key Topics

• Data Communication Protocols: The standard specifies structures for transmitting data between various items of computer equipment used in building control, aligning with international best practices to ensure cross-system compatibility.
• Object-Oriented Modeling: oSIST prEN ISO 16484-5:2026 introduces an abstract, object-oriented representation of building system information, allowing standardization in how diverse devices and systems report and interpret data.
• BACnet Protocol Architecture: The core of the standard encompasses BACnet architecture, addressing layered network design, network topologies, and system security considerations.
• Application & Network Layers: Detailed guidance is given for application layer models, network layer services, and message segmentation, as well as protocols for device and data management.
• Wide Range of Communication Media: The standard provides specifications for Ethernet (ISO 8802-3), ARCNET, MS/TP, Point-to-Point (PTP), and LonTalk (ISO/IEC 14908-1) local area networks, ensuring support for both legacy and modern networking environments.
• Device and Object Types: Comprehensive object models are described for commonly used automation components, such as analog/binary input and output, scheduling, trend logging, access control, and lighting.

Applications

oSIST prEN ISO 16484-5:2026 is widely applicable in the design, integration, and operation of building automation and control systems. Major areas of use include:

• HVAC Control: Standardized communication across heating, ventilation, and air conditioning systems ensures efficient operation and integrated energy management.
• Lighting and Access Management: Enables seamless integration of lighting controls, security systems, and access points with centralized management platforms.
• Interoperable Building Systems: The standardized protocol supports multi-vendor and multi-device environments, reducing compatibility issues and future-proofing building automation investments.
• Energy and Facility Management: The standard supports monitoring, trend logging, and audit reporting for energy usage, contributing to enhanced sustainability and operational insight.
• Remote Device Management: Protocols for networked device discovery, configuration, backup/restore, and security serve smart building management requirements, both on-premises and remotely.

Related Standards

When implementing oSIST prEN ISO 16484-5:2026, organizations and system integrators may also reference the following related standards:

• EN ISO 16484-1: Building automation and control systems - Overview and general requirements.
• EN ISO 16484-2: Hardware requirements for BACS components.
• EN ISO 16484-3: Functions and system integration for building control.
• EN ISO 16484-4: Applications software for BACS.
• ISO/IEC 14908-1: Communication protocol for control networks (LonTalk).
• ISO 8802-3 (IEEE 802.3): Ethernet standard for physical layer specifications and media access.

By aligning with oSIST prEN ISO 16484-5:2026, organizations can achieve robust, secure, and flexible building automation systems, driving operational efficiency and supporting sustainable building management objectives.

Keywords: Building automation and control systems, BACS, BACnet, data communication protocol, HVAC control, building systems integration, object-oriented modeling, smart building standards, interoperability, building networks.

Standards Content (Sample)

SLOVENSKI STANDARD
01-junij-2026
Sistemi za avtomatizacijo in regulacijo stavb - 5. del: Protokol za izmenjavo
podatkov (ISO/DIS 16484-5:2026)
Building automation and control systems (BACS) - Part 5: Data communication protocol
(ISO/DIS 16484-5:2026)
Systeme der Gebäudeautomation - Teil 5: Datenkommunikationsprotokoll (ISO/DIS
16484-5:2026)
Systèmes de contrôle et d'automatisation des bâtiments (BACS) - Partie 5: Protocole de
communication de données (ISO/DIS 16484-5:2026)
Ta slovenski standard je istoveten z: prEN ISO 16484-5
ICS:
35.240.67 Uporabniške rešitve IT v IT applications in building
gradbeništvu and construction industry
97.120 Avtomatske krmilne naprave Automatic controls for
za dom household use
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

FINAL DRAFT
International
Standard
ISO/FDIS 16484-5
ISO/TC 205
Building automation and control
Secretariat: ANSI
systems (BACS) —
Voting begins on:
2026-04-02
Part 5:
Data communication protocol
Voting terminates on:
2026-06-25
Systèmes de contrôle et d'automatisation des bâtiments
(BACS) —
Partie 5: Protocole de communication de données
This document is circulated as received from the committee secretariat.
FAST TRACK PROCEDURE
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 16484-5:2026(en) © ISO 2026

FINAL DRAFT
ISO/FDIS 16484-5:2026(en)
International
Standard
ISO/FDIS 16484-5
ISO/TC 205
Building automation and control
Secretariat: ANSI
systems (BACS) —
Voting begins on:
Part 5:
Data communication protocol
Voting terminates on:
Systèmes de contrôle et d'automatisation des bâtiments
(BACS) —
Partie 5: Protocole de communication de données
This document is circulated as received from the committee secretariat.
FAST TRACK PROCEDURE
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 16484-5:2026(en) © ISO 2026

ii
ISO/FDIS 16484-5:2026(en)
CONTENTS
Foreword . xi
FOREWORD . xii
1 PURPOSE . 1
2 SCOPE . 1
3 DEFINITIONS . 1
3.1 Terms Adopted from International Standards . 1
3.2 Terms Defined for this Standard . 2
3.3 Abbreviations and Acronyms Used in this Standard . 8
4 BACnet PROTOCOL ARCHITECTURE. 12
4.1 The BACnet Collapsed Architecture . 13
4.2 BACnet Network Topology . 15
4.3 Security . 16
5 THE APPLICATION LAYER . 17
5.1 The Application Layer Model . 17
5.2 Segmentation of BACnet Messages . 23
5.3 Transmission of BACnet APDUs . 24
5.4 Application Protocol State Machines . 28
5.5 Application Protocol Time Sequence Diagrams . 46
5.6 Application Layer Service Conventions . 55
6 THE NETWORK LAYER . 57
6.1 Network Layer Service Specification . 57
6.2 Network Layer PDU Structure. 59
6.3 Messages for Multiple Recipients . 65
6.4 Network Layer Protocol Messages . 65
6.5 Network Layer Procedures . 69
6.6 BACnet Routers . 71
6.7 Point-To-Point Half-Routers . 76
7 DATA LINK/PHYSICAL LAYERS: Ethernet (ISO 8802-3) LAN . 81
7.1 The Use of ISO 8802-2 Logical Link Control (LLC) . 81
7.2 Parameters Required by the LLC Primitives . 81
7.3 Parameters Required by the MAC Primitives . 81
7.4 Physical Media . 81
8 DATA LINK/PHYSICAL LAYERS: ARCNET (ATA 878.1) LAN . 82
8.1 The Use of ISO 8802-2 Logical Link Control (LLC) . 82
8.2 Parameters Required by the LLC Primitives . 82
8.3 Mapping the LLC Services to the ARCNET MAC Layer . 82
8.4 Parameters Required by the MAC Primitives . 82
8.5 Physical Media . 82
9 DATA LINK/PHYSICAL LAYERS: MULTIDROP SERIAL BUS/TOKEN PASSING (MS/TP) LAN . 84
9.1 Service Specification . 84
9.2 Physical Layer . 86
9.3 MS/TP Frame Format . 96
9.4 Overview of the MS/TP Network . 98
9.5 MS/TP Medium Access Control . 99
9.6 Cyclic Redundancy Check (CRC) . 120
9.7 Interfacing MS/TP LANs with Other BACnet LANs . 121
9.8 Responding BACnet User Processing of Messages from MS/TP . 121
9.9 Repeaters . 122
9.10 COBS (Consistent Overhead Byte Stuffing) Encoding . 123
9.11 Documenting MS/TP Node Design Choices . 127
10 DATA LINK/PHYSICAL LAYERS: POINT-TO-POINT (PTP) . 128
10.1 Overview . 128
10.2 Service Specification . 128
10.3 Point-to-Point Frame Format . 133
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ISO/FDIS 16484-5:2026(en)
10.4 PTP Medium Access Control Protocol . 135
11 DATA LINK/PHYSICAL LAYERS: LonTalk (ISO/IEC 14908.1) LAN . 157
11.1 The Use of ISO 8802-2 Logical Link Control (LLC) . 157
11.2 Parameters Required by the LLC Primitives . 157
11.3 Mapping the LLC Services to the LonTalk Application Layer. 157
11.4 Parameters Required by the Application Layer Primitives . 157
11.5 Physical Media . 158
12 MODELING CONTROL DEVICES AS A COLLECTION OF OBJECTS . 160
12.1 Object Characteristics and Requirements . 160
12.2 Analog Input Object Type . 167
12.3 Analog Output Object Type . 174
12.4 Analog Value Object Type . 182
12.5 Averaging Object Type . 190
12.6 Binary Input Object Type . 194
12.7 Binary Output Object Type . 201
12.8 Binary Value Object Type . 210
12.9 Calendar Object Type . 218
12.10 Command Object Type . 221
12.11 Device Object Type . 228
12.12 Event Enrollment Object Type . 244
12.13 File Object Type . 253
12.14 Group Object Type . 257
12.15 Life Safety Point Object Type . 260
12.16 Life Safety Zone Object Type. 268
12.17 Loop Object Type . 276
12.18 Multi-state Input Object Type . 286
12.19 Multi-state Output Object Type . 292
12.20 Multi-state Value Object Type. 299
12.21 Notification Class Object Type . 307
12.22 Program Object Type . 313
12.23 Pulse Converter Object Type . 320
12.24 Schedule Object Type . 328
12.25 Trend Log Object Type . 336
12.26 Access Door Object Type . 347
12.27 Event Log Object Type . 357
12.28 Load Control Object Type . 365
12.29 Structured View Object Type . 376
12.30 Trend Log Multiple Object Type . 381
12.31 Access Point Object Type . 391
12.32 Access Zone Object Type . 409
12.33 Access User Object Type . 418
12.34 Access Rights Object Type . 422
12.35 Access Credential Object Type . 429
12.36 Credential Data Input Object Type . 439
12.37 CharacterString Value Object Type . 446
12.38 DateTime Value Object Type . 453
12.39 Large Analog Value Object Type . 459
12.40 BitString Value Object Type . 467
12.41 OctetString Value Object Type . 474
12.42 Time Value Object Type . 479
12.43 Integer Value Object Type . 485
12.44 Positive Integer Value Object Type . 493
12.45 Date Value Object Type . 501
12.46 DateTime Pattern Value Object Type . 507
12.47 Time Pattern Value Object Type . 513
12.48 Date Pattern Value Object Type . 519
12.49 Deleted Clause . 525
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ISO/FDIS 16484-5:2026(en)
12.50 Global Group Object Type . 526
12.51 Notification Forwarder Object Type . 534
12.52 Alert Enrollment Object Type . 542
12.53 Channel Object Type . 546
12.54 Lighting Output Object Type . 557
12.55 Binary Lighting Output Object Type . 575
12.56 Network Port Object Type . 587
12.57 Timer Object Type . 629
12.58 Elevator Group Object Type . 642
12.59 Lift Object Type . 646
12.60 Escalator Object Type . 659
12.61 Accumulator Object Type . 667
12.62 Staging Object Type . 677
12.63 Audit Reporter Object Type. 688
12.64 Audit Log Object Type . 694
12.65 Color Object Type . 701
12.66 Color Temperature Object Type . 707
13 ALARM AND EVENT SERVICES . 714
13.1 Change of Value Reporting . 714
13.2 Event Reporting . 719
13.3 Event Algorithms . 732
13.4 Fault Algorithms . 764
13.5 AcknowledgeAlarm Service . 772
13.6 ConfirmedCOVNotification Service . 774
13.7 UnconfirmedCOVNotification Service. 776
13.8 ConfirmedEventNotification Service . 777
13.9 UnconfirmedEventNotification Service . 780
13.10 GetAlarmSummary Service . 783
13.11 GetEnrollmentSummary Service . 785
13.12 GetEventInformation Service . 788
13.13 LifeSafetyOperation Service . 791
13.14 SubscribeCOV Service . 793
13.15 SubscribeCOVProperty Service . 796
13.16 SubscribeCOVPropertyMultiple Service . 799
13.17 ConfirmedCOVNotificationMultiple Service . 805
13.18 UnconfirmedCOVNotificationMultiple Service . 808
13.19 AuditLogQuery . 810
13.20 ConfirmedAuditNotification . 814
13.21 UnconfirmedAuditNotification . 815
14 FILE ACCESS SERVICES . 816
14.1 AtomicReadFile Service . 816
14.2 AtomicWriteFile Service . 819
15 OBJECT ACCESS SERVICES . 822
15.1 AddListElement Service . 822
15.2 RemoveListElement Service . 825
15.3 CreateObject Service . 827
15.4 DeleteObject Service . 830
15.5 ReadProperty Service . 831
15.6 Deleted Clause . 833
15.7 ReadPropertyMultiple Service . 834
15.8 ReadRange Service . 837
15.9 WriteProperty Service . 845
15.10 WritePropertyMultiple Service . 848
15.11 WriteGroup Service . 851
16 REMOTE DEVICE MANAGEMENT SERVICES . 853
16.1 DeviceCommunicationControl Service . 853
16.2 ConfirmedPrivateTransfer Service . 855
v
ISO/FDIS 16484-5:2026(en)
16.3 UnconfirmedPrivateTransfer Service . 857
16.4 ReinitializeDevice Service . 858
16.5 ConfirmedTextMessage Service . 860
16.6 UnconfirmedTextMessage Service . 862
16.7 TimeSynchronization Service . 863
16.8 UTCTimeSynchronization Service . 864
16.9 Who-Has and I-Have Services . 865
16.10 Who-Is and I-Am Services . 867
16.11 Who-Am-I and You-Are Services . 869
17 AUTHENTICATION AND AUTHORIZATION SERVICES . 872
17.1 Overview . 872
17.2 Trust of Intermediaries . 873
17.3 Authentication . 874
17.4 Authorization . 876
17.5 Conformance Requirements. 882
17.6 AuthRequest Service. 883
18 ERROR, REJECT, and ABORT CODES . 887
18.1 Error Class - DEVICE . 887
18.2 Error Class - OBJECT . 887
18.3 Error Class - PROPERTY . 888
18.4 Error Class - RESOURCES . 890
18.5 Error Class - SECURITY . 890
18.6 Error Class - SERVICES . 892
18.7 Error Class - COMMUNICATION . 893
18.8 Error Class - VT . 898
18.9 Reject Reason . 898
18.10 Abort Reason . 899
18.11 Confirmed Service Common Errors . 900
19 BACnet PROCEDURES . 901
19.1 Backup and Restore . 901
19.2 Command Prioritization . 906
19.3 Device Restart Procedure . 911
19.4 Determining Maximum Conveyable APDU . 912
19.5 Value Source Mechanism . 914
19.6 Audit Logging . 916
19.7 Unconfigured Device Discovery and Address Assignment . 927
19.8 Replacing Certificates in a BACnet/SC Network . 928
19.9 Device Address Proxying . 930
20 ENCODING BACnet PROTOCOL DATA UNITS . 934
20.1 Encoding the Fixed Part of BACnet APDUs . 935
20.2 Encoding the Variable Part of BACnet APDUs . 947
21 FORMAL DESCRIPTION OF APPLICATION PROTOCOL DATA UNITS . 963
21.1 APDU Definitions . 963
21.2 Confirmed Service Productions . 965
21.3 Unconfirmed Service Productions . 976
21.4 Error Productions . 980
21.5 Application Types . 992
21.6 Base Types . 994
22 CONFORMANCE AND INTEROPERABILITY . 1082
22.1 Conformance to BACnet . 1082
22.2 BACnet Interoperability . 1083
23 EXTENDING BACnet TO ACCOMMODATE VENDOR PROPRIETARY INFORMATION. 1085
23.1 Extending Enumeration Values . 1085
23.2 Using the PrivateTransfer Services to Invoke Non-Standardized Services . 1086
23.3 Adding Proprietary Properties to a Standardized Object . 1086
23.4 Adding Proprietary Object Types to BACnet . 1087
23.5 Restrictions on Extending BACnet . 1087
vi
ISO/FDIS 16484-5:2026(en)
24 DELETED CLAUSE . 1088
25 REFERENCES . 1089
ANNEX A - PROTOCOL IMPLEMENTATION CONFORMANCE STATEMENT (NORMATIVE) . 1094
ANNEX B - GUIDE TO SPECIFYING BACnet DEVICES (INFORMATIVE) . 1098
ANNEX C - Removed . 1099
ANNEX D - Removed . 1100
ANNEX E - EXAMPLES OF BACnet APPLICATION SERVICES (INFORMATIVE) . 1101
E.1 Alarm and Event Services . 1101
E.2 File Access Services . 1106
E.3 Object Access Services . 1107
E.4 Remote Device Management Services . 1114
E.5 Virtual Terminal Services . 1117
ANNEX F - EXAMPLES OF APDU ENCODING (INFORMATIVE) . 1120
F.1 Example Encodings for Alarm and Event Services . 1120
F.2 Example Encodings for File Access Services . 1131
F.3 Example Encodings for Object Access Services . 1134
F.4 Example Encodings for Remote Device Management Services . 1144
F.5 Example Encodings for Virtual Terminal Services . 1150
ANNEX G - CALCULATION OF CRC (INFORMATIVE) . 1153
G.1 Calculation of the Header CRC .
...