Best practices for building integration and interoperability

Many benefits to building integration include efficiency and reduced maintenance, when best practices are followed during the design process.
By Terry Flock, PE; Doug Showers, PE; and Jeremy Lang, CCNA-I; Affiliated Engineers September 20, 2017

This article has been peer-reviewed.Learning objectives:

  • Understand the basics of building system integration.
  • Learn about the drivers behind designing integrated systems, such as system performance.
  • Assess examples of integrating building systems.

Today, it seems that almost any daily task can be done with the click of a mouse or swipe of a finger. This convenience has led to some assumptions that a modern building automation system (BAS) will be able to deliver this same functionality. With sufficient upfront thought and planning, system functionality of unprecedented versatility and impact is possible using integration and interoperability. Projects must be designed with an understanding of how different systems can work together and what is possible to provide the features that the user and owner are expecting. However, the user and the owner must first be made aware of the opportunities to gain additional functionality for little to no added cost.

Defining interoperability and integration

Figure 1: The owner’s goal for this office building was to create an exceptional occupancy experience using minimal resources. All graphics courtesy: Affiliated Engineers Inc.From a controls perspective, interoperability is the ability of different systems to communicate using a common communication protocol. For building automation systems, interoperability typically involves BACnet, Modbus, and local operating networks (LonWorks) communication protocols, which allow different manufacturers’ equipment a way to communicate and share data. Traditional analog and digital hardwired signals are still used for simple interoperable interfaces including permissives and safety locks. Permissives are several process conditions that must be met before a piece of equipment is allowed to start.

In the building controls world, integration is the process of connecting multiple systems that control or monitor separate equipment by using interoperable parts to provide a single functioning system. Systems may be interoperable, but integration is required to make them function together.

Why do we integrate?

A building consists of a combination of many different systems and equipment that are built by different manufacturers and installed/commissioned by different contractors. An integrated building provides visibility in several ways: visibility of data analysis tools, visibility of building status to operations, and visibility of performance to building owners. When and how to coordinate the integration is a key consideration. Coordination can begin during schematic design, especially if the project is structured as design-build or design-assist, by leveraging the presence of the construction team. This allows contractors and construction managers to start understanding the level of systems involved. Understanding the payback on an investment of integrating many systems is multifaceted and complicated. Cabling costs, system-integration labor, design labor, and distributors are all things to consider as added costs. The key question concerns how quickly those costs can be offset and whether that is measurable. According to the Continental Automated Building Association, a cable-reduction savings of 56% can be realized by integrating systems and sharing cable and pathways.

 Figure 2:  The rewards for integration and interoperability are high and provide a means to increase efficiency, comfort, and reliability, and to reduce maintenance for the life of a building. What once was optional is becoming standard practice.Energy efficiency and system performance are important reasons to integrate systems. Electricity, natural gas, hot water, chilled water, and steam are common utilities in a building. For energy purposes, real-time energy demand and consumption can be trended and exported for analysis to find opportunities to improve system performance. Natural gas and electricity are usually metered by the utility provider at a building entry point for billing purposes, but for many buildings, these meters are not integrated despite the low cost—even no cost—of doing so. If energy efficiency and conservation are the main goals, then an integrated design can easily accommodate the addition of pulse output signals from the natural gas and electrical meter. Most electrical meters come standard with Modbus remote terminal unit (RTU) or Modbus transmission control protocol/internet protocol (TCP/IP) communications for additional integration opportunities that provide a more granular understanding of energy consumption and demand. The information garnered from such an interface ranges from power usage and quality to system health. Chilled-water and hot-water systems are typically designed with temperature and flow measurements that can easily be upgraded to an energy-consumption meter.

Integration can save energy through increased system performance. When packaged air handling units (AHUs) can communicate with air terminal devices, opportunities are available to reset AHU discharge temperature and pressure based on actual conditions. If lighting and HVAC occupancy times are automatically coordinated, energy savings are maximized. Integrating occupancy signals from the access-control system provides additional advanced opportunities for the BAS to determine the actual occupancy of the building and update ventilation setpoints and lighting levels based on this information.

Figure 3: Integration is connecting multiple systems that control or monitor separate pieces of equipment by using interoperable parts to provide a single functioning system. Integration is required to make interoperable systems function together.Another important reason to integrate is maintenance. Many maintenance personnel are expected to retire within the next 5 years. The facility manager for a Midwestern health care client recently determined 54% of their maintenance staff is expected to retire in the next 5 years. Staff counts are decreasing, yet the complexity in systems is increasing, usually to meet energy goals. If these advanced mechanical systems cannot be maintained, they will in some cases decrease system efficiency. For example, a heat-recovery system operating with a faulty temperature sensor may be running when it is not advantageous to save energy, resulting in wasting pumping energy, which adds to operational costs. This gap can be filled using technology and running reports to verify system health. Islanded subsystems, or systems installed without any connection to the overall network, make maintaining systems very difficult and will impact building performance for the life of the systems.

Another example of increasing staff efficiency is integrating the building automation system with a computerized maintenance management system (CMMS). This gives the maintenance staff the added efficiency of automatically generating work orders.  

Increased occupant comfort is a byproduct of integration. System data that’s introduced into the building network can be analyzed and alarmed by the BAS or interfaced with third-party fault-detection and diagnostics applications. Having all the data in one historical database is a crucial tool for troubleshooting. Visibility of systems helps increase overall reliability and resiliency by exposing data that can be used to adjust parameters, calibration, and maintenance schedules. Equipment status and operational deviations allow for proactive maintenance instead of emergency reactions.

The phases of a successful integration

Figure 4: The payback on an investment of integrating many systems is multifaceted and complicated. A key concern is how quickly additional costs can be offset and whether the savings is measurable.Standards focusing on interoperability exist (like BACnet), yet guiding standards focusing on building-integration best practices are limited. It is often left up to the controls contractor or system integrator to provide their off-the-shelf solution. In this article, we are going to refer to controls contractors that integrate multiple systems as “systems integrators” because of the added expectations of integration. Most system integrators and controls contractors have their own equipment or controllers for similar applications. A typical controls contractor is not necessarily concerned about whether the integration is successful or not, where a system integrator is concerned. This is where it is important to understand what system is being provided and what limitations may be present. For example, some controls contractors lock points available to BACnet if not specified to be exposed. Additional integration challenges include the constant evolution of software and hardware, low-bid integrator selection, time constraints, training, legacy systems, and poorly defined requirements.

Owner and user requirements: The first steps of a successful integration project are obtaining a clear understanding of the owner’s and design team’s expectations and requirements, then consulting with the owner and design team on what is possible. Almost all equipment today comes standard with a BACnet, Modbus, or LonWorks interface. Some owners have strong opinions and detailed expectations for integration while others only have general requirements. Typical clarification questions should include:

  • What level of integration is desired (e.g., mechanical systems, specialty systems, metering, lighting, load shedding, smoke control, shades, security, etc.)?
  • Is there a desire to only monitor specific points versus control and monitor?
  • Is the owner happy with their existing building controls?
  • Is the owner looking for an open system?
  • Will maintenance and operations be contracted out or performed by internal staff?

Figure 5: An ideation session with the owner, participants from all user groups, and the design team helps to establish an overall architecture that defines and identifies the systems to be integrated.The designer should indicate to the owner integration opportunities that can provide the most initial value (e.g., integrating the lighting control system into the BAS) and those that are possible at little to no cost (e.g., chillers, boilers, variable frequency drives, etc.). Regardless of whether a given system will be integrated during the initial installation, the design engineer should plan for these systems and provide all prerequisites in the initial design. For example, the network infrastructure should be sufficient to support future integrations, wall space should be reserved if additional control panels are required, and communication protocols should be reviewed.

One way to prioritize goals is through an ideation session with all stakeholders. An ideation session, or workshop, is a forum to spotlight and prioritize goals and objectives. Participants from all user groups should be included. From meetings with the owner and design team, an overall system architecture can be created that defines and identifies the system to be integrated as well as communication protocols, network hardware, controllers, workstations, servers, and software to be used. Figure 5 is an image of a typical system architecture that would be developed during design. Other key tools used in the design of an interoperable integrated system include instrumented flow diagrams, points list, sequences, and specifications.

Routing data: Coordination that must occur with the information technology (IT) network is one of the most important parts of integration today. Designers responsible for integration must understand capabilities of IT systems and have a good working relationship with the IT design engineer to coordinate the distribution of data from the edge, or end, device up the corporate value chain. It’s nearly impossible for an engineer focusing on integration to have an exhaustive knowledge of all pertinent data sources and volume. For instance, fiber-optic cable alone has several parameters that must be specified per the application. An IT engineer will know best how to specify the fiber parameters, such as glass/transmission type, strand count, construction (e.g., armored loose tube), rating, connectors, and termination type.

An integrated and interoperable building needs to share network resources. This makes sense as a way to leverage the IT infrastructure to serve multiple systems, allowing owners to maximize investments. Most platforms today—such as a lighting system, fire alarm system, or clock system—use the bottom three layers of the open systems interconnection (OSI) model, allowing the IT infrastructure to transfer data.

Today’s network switches are capable of handling the volume and speed required to successfully transfer data packets from several systems. But what happens in the unlikely event of congestion? For years now, switches have had the ability to apply data prioritization to packets using quality of service and policing techniques. This allows more critical safety-related data to take precedence over standard data, such as HVAC information. Systems that were once separated with physical local area networks, known as LANs, can now be virtually separated using virtual local area networks, aka VLANs. This Layer 2 isolation method not only provides congestion mitigation, it also adds a simple level of security to the network.

Routing data is the key to integration. Routing allows for devices on different networks to come together in one specific place. For example, a lighting control system can pass occupancy information onto the same database as the BAS. Running data analytics rules becomes a whole lot easier when data is in one place. In a typical building application, the owner provides the network that is used by the many systems. As the volume of systems needing visibility increases, so does the importance of coordinating the navigation of data packets. What was once a coordination effort between IT and the system integrator must now be realized at the design level. One reason for this is security. Network switches are becoming more mindful of intrusions, making it far more difficult to just “plug in” another controller at the nearest port. Switch interfaces are more routinely configured to disable a port, or even neighboring ports, if an unknown media access control address (MAC) address attempts to communicate. This can be detrimental if a neighbor port is managing prioritized information, such as a fire alarm system.

Coordination: Working with the mechanical, electrical, and piping engineer is another critical design activity needed to achieve an interoperable integrated building. From this effort, systems are defined by creating instrumented flow diagrams for mechanical and piping systems. An instrumented flow diagram is a schematic representation of a system, such as a heating hot-water system or AHU, which includes equipment, general piping configuration, control valves, control dampers, instrumentation, and input/output points, allowing individuals to quickly understand the system’s configuration.

An instrumented flow diagram can be considered a simplified piping and instrumentation diagram (P&ID) for those familiar with the process industry. The instrumented flow diagram provides the design team with an effective tool to convey design intent to contractors and is more effective than using only mechanical floor plans. An instrumented flow diagram illustrates hard-wired connections to individual instrumentation points as well as networked interface connections. It does not, however, describe the points within a networked interface connection. Instrumented flow diagrams are typically used as the basis for developing control sequences and points lists. Using a standardized tagging and point-naming convention for equipment on the instrumented flow diagram is a best practice to allow use of relational data. This allows users to easily find and analyze points, and new equipment or changes can quickly be incorporated into the systems.

If the intent is to use a data-analytics package, the standardized tagging becomes essential. Typically, the electrical systems integration (e.g., lighting and power monitoring) shows up on the system architecture and points list only and references the electrical drawings and specifications for more detail.

Points lists: After the instrumented flow diagrams are created, a points lists should be developed as early as possible. The points list is a table that describes every input and output point, both hardwired and those points acquired via a network/communications connection. This document can include alarm values, analog scaling (if known), point function, and in some cases, clarification notes. Most network/communications connections between a piece of equipment and a controller contain tens, maybe hundreds, of input/output points. Many of those points are not required for control function and data analysis. The points list only contains the points that the designer feels are necessary. The points list should be discussed with the owner and design team so desired points can be identified. An allowance for additional points can be made to ensure any points found to be necessary during commissioning and start-up can be added. Too often, this is not discussed during the design phase, and the system integrator has to decide which points to bring forward. Many times, they will just map all points that are available so nothing is missed. This ensures all the points the user actually wants will be included, but also adds a significant number of unnecessary points, potentially in the hundreds. This is compounded if it is done for several devices. Electric meters and variable frequency drives (VFDs) are good examples of this. Both have a large number of points and parameters available, and usually substantial numbers of these are within a building.

Sequences: Mechanical and piping engineers develop control sequences for their systems to describe how each system operates. The sequences typically focus on operation functionality. The design engineer must understand how all systems within the building are intended to operate, as well as their interaction with other systems, for integration to be leveraged. Typically, sequences need to be expanded with a focus on integration to include such items as data storage, reports, fault detection and diagnostics, alarming, scheduling, metering, lighting control, load shedding, shade control, and security.

For example, if the power meters do not integrate into the BAS, the opportunity to implement load shedding is lost along with the ability to peak shave and reduce utility bills. ASHRAE Guideline 36: The Next Generation Control System is being created to publish “best-of-class” control sequences. To take advantage of the sequences, in many cases a coordinated system architecture, a points list, and equipment specifications will be required for proper implementation.

Specifications: While creating integration specifications, the design engineer should ask and understand why the systems are being integrated. Once the intended purpose of the integration is understood, the design engineer must determine what can be accomplished. Is the goal to read and store data for trending and analysis only? Or is the goal also to include control of the equipment via communication link? This scope must be clearly specified and conveyed to the system integrator along with equipment providers or other system providers.

The design engineer also must determine the best way to integrate two given systems. For example, automatic transfer switches (ATSs) often must be monitored by the BAS to determine when the building has switched from normal to emergency power. The design engineer must decide whether this should be done via hardwire interlocks or through a communication interface. This is an example of an instance when the reliability of the different options must be thoroughly examined. If the interlocks are through a communication interface, the power source to the controller monitoring the status of the ATSs must be considered. Examples of questions that could be asked during the design phase are:

  • What happens if/when it loses power?
  • What happens if other controllers/devices on the same communication bus lose power and stop communicating?
  • How compatible are the two systems?
  • Are there any limitations to what can be done?

A properly edited set of specifications is required for this. Specifying integration includes editing the controls and communications portion of equipment specifications (e.g., primary cooling equipment, primary heating equipment, packaged AHUs, VFDs, water heaters, electrical power monitoring, ATSs, and lighting). Other items to include are hardwired signals and joint commissioning and start-up with the controls contractor. Specifying the scope for both the equipment supplier and control contractor is very important; otherwise, start-up assistance may not be included. The integration will not be successful if both parties are not responsible for making the integration work. This includes items in the points list, as well as specifying who is responsible for providing the integration equipment.

Typically, having the equipment supplier provide the communication interface is preferable. It is becoming very common for original equipment manufacturers (OEMs) to offer a communication interface for several protocols, such as BACnet, Modbus, or LonWorks. Best practices involve eliminating third-party translators and selecting devices already with open interoperable protocols.

Life safety integration: Many controls contractors offer the capability to provide UL 864 controllers, which allows integrating smoke-control systems into the building automation system, thus eliminating the need for both the fire alarm system and the BAS to control smoke-control equipment. When integrating equipment dedicated for smoke control, all components of the smoke-control system must be UL 864-listed. Careful consideration should be given to this before proceeding. It is recommended that the owner and design team conduct an evaluation of pros and cons and discuss this with the local authority having jurisdiction before proceeding with the integration. Advantages include reducing cost, saving space by sharing equipment, and increasing flexibility. Disadvantages include lack of contractor and user familiarity, additional operational testing, and BAS upgrades that may require recommissioning of the smoke-control system.

Construction: The final phase of integration, construction is the most critical. This starts with selecting systems integrators to bid on the work. Integration work is highly dependent on the skills and training of the staff implementing the solutions. Selecting a contractor with a proven history is crucial. Reviewing submittals to make sure the protocols and features specified are provided is just as important, including those for packaged equipment, such as AHUs, chillers, and boilers. If equipment shows up onsite without the proper communications and configuration, delays may result and features may not be implemented.

Allowing time for and scheduling joint start-up and commissioning of integrated systems must be completed for the integration to be successful. Integrated systems must be thoroughly tested to prove functionality. Adjustment and operational modifications to the systems should be expected once systems are operational. Pretesting programming code and simulating sequences are also highly recommended and can highlight problem areas in advance of start-up.

Sometimes, it may be necessary for the controls contractor or system integrator to provide temporary Ethernet switches to commission the system if the IT infrastructure is not ready. Specifications should address this so final commissioning is completed with the permanent IT infrastructure.

Many integrated buildings go through a phased integration approach. During the construction of a new building, there are typically time constraints on contractors to get the building systems operating so the facility can be occupied. A layered integration approach works well in these instances. After the base-system functionally is proven and commissioned, personnel can be trained and become familiar with their new facility. Additional layers of integration can then be added and commissioned as facility personnel become comfortable with how the systems are operating.

Integrating systems into a BAS requires experience in many areas to orchestrate and fully leverage its many facets. The benefits of integration are high and provide a means to increased efficiency, comfort, reliability, and a reduction of maintenance for the life of the building. Building evolution continues to push the boundaries of integrated systems to the next level, and owners’ expectations continue to grow. What once was an option is becoming a standard practice.

Projects using best practices for integration and interoperability

A brownfield, high-rise office building in a midsize Midwestern city went through the design practices described in the article. The owner’s goals for the project were to create an exceptional occupancy experience using minimal resources. The owner had a strong desire to make the building equally innovative, sustainable, and intelligent. An ideation session was held with the design team and owner to identify integration opportunities and ultimately define the level of integration desired. Not all the integration ideas were incorporated into the design. The design of the core infrastructure accounted for future integration goals while the initial build-out included electric power demand and consumption integration—as well as hot-water and chilled-water energy rate and consumption. Other systems, such as low-temperature condensing boilers, magnetic bearing chillers, and an emergency generator, were integrated with the building automation system (BAS). The lighting system was integrated with the automated shade controls and with the HVAC system for occupancy control. One reason for integrating these systems was the need for energy reports and long-term storage of performance data. Points to be trended were defined with a sample interval taken every 15 minutes and automated reports running every hour. Data and reports were specified to be saved for a minimum of 36 months. In addition, the data within the reports will be broken down and grouped into several different categories, based on the types of loads they serve within the building.

The Bay Area Medical Center project in Marinette, Wis., is a greenfield hospital and medical office building designed to support emerging practices and technologies and provide the best state-of-the-art care. Because budgets were limited, efforts were made to contain installation costs while still looking for building-intelligence opportunities supporting long-term staffing challenges and system health. Long-term data storage was presented and accepted as a low-cost solution but required an integration effort to accumulate data from several systems. Integrated systems included a BAS connection to the lighting control system for occupancy and lighting control. In addition, the BAS was integrated into the medical-gas alarm system for both reporting and long-term tracking. Finally, the switchgear was specified to include a BACnet master slave token passing (MS/TP) translator for interfacing into the BAS for electrical distribution status.


Terry Flock is an instrumentation and controls project manager with Affiliated Engineers Inc. Doug Showers is an instrumentation and controls project engineer with Affiliated Engineers Inc. Jeremy Lang is an instrumentation and controls project designer with Affiliated Engineers Inc.