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.

03/26/2014


Learning Objectives

  1. 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.
  2. Know which performance metrics are most important to measure the efficiency of a building.
  3. Learn about the codes and standards that govern Cx of high-performance buildings.

This article has been peer-reviewed.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.

Figure 1: This shows a sample of RCx tasks and project schedule for a Tier III data center with nominal capacity of 8 MW. As shown in this figure, the RCx and the M&V part of it is very data driven with a lengthy implementation time period that could takes up to a few months to be completed. All graphics courtesy: AlfaTech Consulting Engineers

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.

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