What Are BACnet BIBBs? Interoperability Building Blocks Explained
What Are BACnet BIBBs?
BACnet devices can support many different services and capabilities. Simply knowing that two products support BACnet does not guarantee that they can perform every function required by a building automation system.
BACnet Interoperability Building Blocks, or BIBBs, provide a standardized way to describe those capabilities.
A BIBB identifies a specific interoperability function that a BACnet device supports. Engineers, system integrators, and product developers can compare the BIBBs supported by different devices to determine whether they can perform the required BACnet operations together.
What Does BIBB Mean?
BIBB stands for BACnet Interoperability Building Block.
A BIBB represents a defined BACnet interoperability capability. It may specify one or more BACnet services and additional requirements needed for a device to perform a particular function.
This is different from simply listing the individual BACnet services that a device supports. BIBBs organize those services into useful interoperability capabilities that can be compared between products.
Example: Reading a BACnet Property
Consider a building automation controller that needs to read the temperature setpoint from a BACnet thermostat.
The controller must be able to initiate a ReadProperty request. This capability is described by:
DS-RP-A - Data Sharing, ReadProperty-A
The thermostat must be able to execute the corresponding ReadProperty request and return the requested value:
DS-RP-B - Data Sharing, ReadProperty-B
Supporting BACnet on both devices is not enough by itself. For this particular interaction, the devices need complementary capabilities for the ReadProperty operation.
Example: Writing a BACnet Property
Now consider a building management system that needs to send an outdoor air temperature value or another command to a BACnet controller.
The device initiating the WriteProperty operation may require:
DS-WP-A - Data Sharing, WriteProperty-A
The device receiving and executing the WriteProperty operation may require:
DS-WP-B - Data Sharing, WriteProperty-B
Comparing these BIBBs helps determine whether the two devices support the required BACnet interaction before the equipment is installed.
What Do the A and B Mean in a BIBB?
Many BACnet BIBBs are defined as complementary A and B variants.
In common Data Sharing examples, the A-side device initiates a service and the B-side device executes or responds to that service.
For example:
| BIBB | Capability | Typical Role |
| DS-RP-A | ReadProperty-A | Initiates a ReadProperty request |
| DS-RP-B | ReadProperty-B | Executes a ReadProperty request |
| DS-WP-A | WriteProperty-A | Initiates a WriteProperty request |
| DS-WP-B | WriteProperty-B | Executes a WriteProperty request |
The exact requirements are defined by the individual BIBB. The A and B suffixes should therefore be interpreted according to that BIBB rather than assuming that every BACnet capability follows exactly the same client/server relationship.
BACnet Services vs. BIBBs
A BACnet service is a protocol operation such as ReadProperty, WriteProperty, ReadPropertyMultiple, or SubscribeCOV.
A BIBB describes an interoperability capability and defines the requirements associated with that capability.
For example, ReadProperty is a BACnet service. DS-RP-A and DS-RP-B are BIBBs that describe the complementary capabilities required to use that service in an interoperable system.
Common BACnet BIBB Categories
BIBBs are organized into functional areas that describe different types of BACnet interoperability.
| Prefix | Capability Area | Examples |
| DS | Data Sharing | Reading, writing, and exchanging BACnet values |
| AE | Alarm and Event Management | Alarm notification, event information, and acknowledgement |
| SCHED | Scheduling | Viewing and modifying schedules |
| T | Trending | Viewing and retrieving historical trend information |
| DM | Device Management | Device discovery, time synchronization, backup, and other management functions |
| NM | Network Management | Network and BACnet/IP management functions |
| GW | Gateway | Capabilities associated with gateways and represented devices |
The complete BACnet standard defines the detailed requirements associated with each BIBB. The available BIBBs have also evolved as BACnet has added new capabilities over time.
Why BIBBs Matter for BACnet Interoperability
BIBBs are useful because two BACnet devices can communicate on the same network while still lacking the application capabilities needed for a particular project.
For example, a supervisory system may need to:
- Read point values
- Write commands or setpoints
- Subscribe to Change of Value notifications
- Receive and acknowledge alarms
- Retrieve trend data
- View or modify schedules
- Synchronize device clocks
A device may support some of these functions and not others. Comparing BIBBs provides a standardized way to identify those differences.
BIBBs and the BACnet PICS
When evaluating a BACnet product, one of the most useful documents is its Protocol Implementation Conformance Statement (PICS).
The PICS describes the BACnet capabilities implemented by the product, including supported BIBBs, object types, data-link options, character sets, and other protocol capabilities.
BIBB declarations can therefore be used to compare the functionality of products from different manufacturers before integration begins.
BTL-listed products also provide useful information about the BACnet capabilities that have been tested for the product.
How to Use BIBBs on a BACnet Project
Start with the functions the system needs to perform rather than simply creating a long list of BACnet services.
For example:
| Project Requirement | BIBB Capability to Check |
| BMS must read values from a controller | DS-RP-A on the BMS and DS-RP-B on the controller |
| BMS must write a setpoint | DS-WP-A on the BMS and DS-WP-B on the controller |
| BMS must receive Change of Value updates | Check the applicable Data Sharing COV BIBBs on both devices |
| Operator must receive and acknowledge alarms | Check the applicable Alarm and Event Management BIBBs |
| Operator must retrieve trend data | Check the applicable Trending BIBBs |
| Operator must modify schedules | Check the applicable Scheduling BIBBs |
This approach connects the project requirements directly to the BACnet capabilities required from each device.
BIBBs Do Not Guarantee the Entire Integration
Matching BIBBs is an important part of determining interoperability, but it is not the only consideration.
A successful BACnet integration can also depend on the objects and properties exposed by each device, writable property support, BACnet network configuration, data-link compatibility, routing, device settings, and application-specific behavior.
BIBBs should therefore be used as part of the overall BACnet integration and commissioning process rather than as the only compatibility check.
BACnet BIBB Reference Table
Chipkin maintains a detailed reference containing BACnet BIBB codes, capability areas, and descriptions:
BACnet Interoperability Building Blocks (BIBBs) Reference Table
Use the reference table when you need to look up a specific BIBB. Use this article when you need to understand what BIBBs mean and how they are used when evaluating BACnet interoperability.
Related BACnet Resources
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