Using BAS for M&V
Without knowing the performance metrics of a building, measuring the success of the engineered systems is limited. Engineers should know the process for using BAS for measurement and verification (M&V) as a part of retro-commissioning in high-performance buildings.
- Understand how BAS can assist with the M&V process in retro-commissioning (RCx), existing building commissioning (EBCx), monitoring-based commissioning (MBCx), and ongoing commissioning (Cx) processes.
- Know which performance metrics are most important to measure the efficiency of a building.
- Learn about the codes and standards that govern Cx of high-performance buildings.
Measurement and verification (M&V) for new construction projects includes quality assurance and verification of design intent and/or compliance with U.S. Green Building Council LEED requirements or with emerging codes and standards in some jurisdictions. One of the main goals of M&V for new construction projects is to make sure that the completed project meets the design intent.
As described in LEED for Existing Buildings, M&V in existing building commissioning (Cx) processes is “a systematic process, to develop an understanding of the operation of the building’s major energy-using systems” for retro-commissioning (RCx) agents to develop “options for optimizing energy performance and a plan to achieve energy savings.”
Energy and Atmosphere (EA) Credit 2.3 in LEED for existing buildings requires ongoing Cx, which requires an ongoing Cx process to take place at least every 24 months. In addition to system testing, the ongoing Cx requires planning and performance verification to detect the required corrective action response and proactively address operation and maintenance problems.
Existing building M&V processes
In addition to being used during new construction Cx as described above, M&V techniques can be applied during post-occupancy as a part of RCx, existing building commissioning (EBCx), monitoring-based commissioning (MBCx), or the ongoing commissioning (Cx) process. In some instances, the process serves as a quality assurance measure to document that an improvement delivers the intended savings or performance improvement. Thus, it serves as a quality assurance measure, just as it does for new construction applications. Verifying savings for RCx, EBCx, and MBCx processes that are being driven and funded by utility incentive programs are common examples of this type of application.
It is not uncommon to use the M&V process in a more focused manner in existing building applications. Specifically, the process can be applied to:
- Ensuring the persistence of energy conservation strategies and overall system performance goals
- Diagnosing an operational problem
- Gathering data to inform the analysis and implementation of a proposed improvement.
BAS: A critical player
For virtually any M&V process, the ability to implement the process—and the ultimate success of the effort—will be depend on the capabilities of the BAS. Ultimately, that comes back to the design and architecture of the BAS network.
One of the benefits of involving a commissioning agent (CxA) in the new construction Cx process during the early phases of design is that the agent can assist the project design team in developing a robust BAS infrastructure via the design review process. However, for existing building processes, the Cx team may need to tailor its M&V plan and process to the capabilities of the existing control system. This may mean they need to supplement the BAS with portable data loggers or similar technologies.
If an existing BAS is capable of implementing an extensive M&V plan, there are other challenges to deal with when using this approach. An example of one of those challenges is data analysis, or “data crunching” as it is known in the industry. The extent and complexity of data crunching that will be required is usually a function of the building/facility complexity and the number of existing building Cx measures that are targeted by the project.
Another challenge that often comes when applying an M&V process in an existing building is the available database. It is not uncommon for an existing system to be missing some of the data points required for a thorough analysis. As a result, existing building processes must include a thorough study of the targeted systems to:
- Identify the critical parameters to be measured to quantify system performances during RCx.
- Ensure that sensors are provided at these points in the system. Frequently, operator interviews are employed as a tool for developing an understanding of the existing systems in a facility.
M&V codes and standards
For new construction projects, a number of codes and standards are emerging to drive the process. One of the most common guides driving an M&V process is LEED, which includes general requirements for trend analysis to verify performance as a part of the Energy and Atmosphere credit. Under EA Credit 5 for new construction projects, LEED offers a credit for developing and implementing a full-fledged M&V plan.
In addition to LEED, building codes in a number of jurisdictions are beginning to adopt Cx requirements that include M&V elements. The Seattle and Washington State Energy Codes are examples, in addition to Title 24 in California. In fact, the latest edition of Title 24, which will be effective in mid-2014, will drive new construction Cx processes toward requirements that are very similar to the requirements for LEED fundamental and enhanced Cx.
In contrast, M&V in existing building Cx processes tends to be driven either by the owner or the requirements of a utility incentive program that is funding the project, as mentioned previously. For example, the University of California/California State University/Investor Owned Utility (UC/CSU/IOU) MBCx program generally requires two different forms of M&V:
- For the initial RCx phase, energy savings incentives are based on the difference between a whole building meter consumption baseline, which is established prior to implementation, and the baseline that exists at the whole building meter after implementation.
- For energy conservation measures implemented subsequent to the initial RCx effort, the savings are incented based on engineering calculations. However, the validity of the calculation is frequently verified using M&V strategies, either at the whole building level or at the system level.
Regardless of the Cx process, most M&V standards and code requirements trace their roots to the International Performance Measurement and Verification Protocol (IPMVP). This standard sets rigorous requirements regarding the protocols, methodology, and tools used to quantify resource savings. In general, and with regard to M&V methodologies, IPMVP suggests four options for determining savings, including retrofit isolation by measuring certain key parameters, retrofit isolation by measuring all parameters, whole facility energy measurement, and calibrated simulation.
During a RCx project, depending on owner project requirements (OPR), input from the operation and maintenance (O&M) team during interviews, and the RCx agent site visits and reviews, a set of goals will be introduced as part of an M&V plan draft. This draft will be reviewed by the owner’s team and finalized. This document will define the extent of M&V. In general, a RCx M&V plan includes the following:
- The timing to put the RCx contract in place
- Potential preparations prior to each site visit
- Site visit timing and requirements
- Identification of systems (should be included in the RCx project and are part of the M&V plan)
- Assessment of BAS and control points for each system to identify control points that should be trended
- Identification of tools (direct and/or indirect monitoring) for launching the trending process
- Data analysis schedule
- Development of energy and water saving measures and O&M opportunities
- Quantification of energy and water saving measures
- Writing a draft report, owner’s review, final report issuance, and presentation.
In the past, the BAS was more about automating certain building control tasks. The main, if not only, diagnostic tool for older versions of BAS was relying on heating and cooling complaints or “cold calls.”
The next major advancement in BAS was lighting control and how lighting actions and tasks were automated based on occupancy, daylight, and task type.
One of the main goals of RCx projects is to detect any failed system parts. These faults include both hardware and software. Examples of hardware faults are failed valves, broken or stuck dampers, and noncalibrated or failed sensors.
However, when it comes to M&V and data collection, there are no standard methods, and it is an engineering art to envision the future M&V needs of a facility during the BAS design. Discussion of how BAS can provide the most effective system M&V during the RCx process is important, and should take place during BAS design when the BAS specifications are developed and documented.
In the recent years, BAS has achieved significant progress in hardware faults diagnostics. On the other hand, diagnostic and fault detection of the BAS control sequences is a more challenging task as the software should quality check software. Examples of software faults are self-evaluation of control sequences, design deficiencies or errors, and methodologies of reporting the actionable findings.
It is reasonable to assume that the major part of any fault detection and diagnostic (FDD) software should be based on measurement and verification process. Earlier versions of FDD tools were independent, stand-alone platforms that analyzed the collected trend data generated by the BAS. The FDD platforms usually analyzed these trends that were provided in batch file. One of the challenges with this method is that for the sites with high security protocols, an open bridge in the form of online access to their BAS would not be desirable. Recognizing the prerequisites of a facility’s IT securities is an important consideration when specifying BAS with FDD capabilities. Based on these types of constraints, statistical and numerical analysis, such as normalization and sensitivity analysis, can be done either on the BAS platform or on a cloud-based server. Integration of BAS and FDD tools is an ongoing development effort.
The best way to use a BAS for M&V purposes on a RCx project is to design the BAS with the M&V goals in mind. While data collection and data crunching are an integral part of RCx, as a designer and a specifying consultant, we would not like to be cumbersome or incur many unnecessary costs to the client. To design a robust BAS and to avoid value engineering later in a project, it is important to get input from the owner and O&M staff, while also educating parties involved on the benefits of a robust BAS capable of M&V. This process will help to ensure the inclusion of BAS requirements in the OPR document.
The first cost of installing a BAS with M&V capabilities can be very well justified by RCx benefits. A Lawrence Berkeley National Lab report states that RCx can have energy and maintenance cost savings of about 16%. In addition, a capable BAS can reduce the cost of RCx projects, which in turn enables the building owner and O&M staff to acquire RCx services more often.
Designing a BAS with M&V capabilities is not a task that should be done solely by the control contractor; the design should be a collaborative effort between all design disciplines including MEP, technology and security, process, and owner representatives. In this process, software design strategies and hardware are both required.
Whole-building benchmarking is an effective tool to evaluate the building energy and operation status. A lower building benchmark is an indicator of a building’s plant and system level energy and operational deficiencies. Whole-building level energy benchmarks are created using static data such as historical monthly utility bills, square footages, data representative of plug loads, etc. Whole-building benchmarking engines such as Energy Star use statistical data across the board for many building types, which are collected under different survey programs such as Commercial Building Energy Consumption Survey (CBECS).
One way that BAS can assist M&V is through the use of historical trend data for creating an isolated benchmark. Isolated benchmarking of a building is a comparison of a building with itself. When the BAS or the RCx agent performs a similar analysis, the actionable outcome could determine, for example, why the electrical demand is higher at night than during the day on weekends.
There are two conclusions to draw from this: First, with regard to new construction projects, to design a facility with robust capability for ongoing commissioning, the BAS should be designed with capabilities for conducting data driven M&V. Some of the M&V practices used in the RCx process could be used as guidelines when specifying and designing new building BAS. Some of the M&V tasks, which in most cases are done outside the BAS, can be specified during the control design process to be included as part of the BAS.
The second conclusion deals with existing buildings and showing the importance and advantages of BAS for conducting data driven M&V. To give owner and facility managers the ability to conduct such a data driven process, it is worthwhile to explore necessary upgrades. For potential BAS upgrades to satisfy the M&V, a complete investigation of existing control system hardware, software, and expectations (such as FDD capability) is required.
Moh Heidari is director of the energy solutions group at AlfaTech Consulting Engineers. He has more than 10 years of experience in energy engineering, Cx, RCx, and energy modeling. He has a master’s degree in mechanical engineering.