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Cx Monitor: Adding Greater Value to our Facilities: M&V and MBCx

| Eric Sheffer

Once a facility is built and fully operational, what assurances does the owner have that the building will perform as intended?  Operational energy performance is a priority for building owners, and as the old adage goes, “You can’t manage what you don’t measure.” Without actionable, systems-level data on energy usage for our facilities, performance decay is inevitable.  The LEED rating system has been at the forefront of encouraging the ongoing monitoring of building energy performance.  In this edition of the Cx Monitor, we discuss their past efforts of promoting Measurement and Verification (M&V) and the more recent Monitoring Based Commissioning (MBCx).

A comprehensive approach to metering and monitoring of energy performance addresses this need to measure actual energy consumption within a facility and verify that the intended performance is being maintained or improved.  According to an April 2011 ASHRAE Journal article on Energy Metering, a minimum of 2% of this performance decay can typically be avoided just by measuring energy use and making building operators and occupants aware of their usage.   When energy data is used within the context of a broader M&V or MBCx process, 15% to 45% of this energy decay can be avoided, and performance can be further improved.

During design, the M&V “Planning” phase occurs, during which the energy analyst consults with the Owner on energy management goals for the facility and works with the design team to integrate metering, trending, and reporting requirements into the contract documents.  The International Performance Measurement and Verification Protocol (IPMVP) is the industry standard  typically used to determine the most appropriate option for designing an M&V plan.  Relative to LEED v3, a measurement and verification procedure (per IPMVP Options B or D), satisfies the requirements for Energy and Atmosphere Credit 5 within the Building Design & Construction rating system.  When it comes to designing a metering system, the goal is to utilize the simplest, most cost-effective means feasible of obtaining a useful level of building and system performance data.  In new construction projects, energy models are created for the Proposed and code-minimum Baseline building designs in order to document the achievement of design-phase energy goals.

Once the facility is operational and data trending has been established, a minimum 12-month M&V “Implementation” phase is initiated.  Using actual performance data, weather conditions, occupancy, and building usage, the design phase energy models are calibrated to match the utility bills.  Through the model calibration process, the energy analyst can confirm whether or not the design-phase energy performance goals were realized.  If not, the calibrated models are used either to identify how the facility is being used differently than originally intended or to identify underperforming systems.  With this data, a plan of corrective actions can be created, and the building owner and operators are left with tools for continuous improvement of energy performance.  In SSRCx’s experience, the M&V process typically uncovers significant equipment or operational issues which have arisen since the completion of the building, and also leads to better designs and energy models in the future.

Monitoring-based commissioning (MBCx) has the same goal as M&V, which is to assist the building owner in optimizing facility performance.  However, MBCx puts less emphasis on energy modeling and a greater emphasis on real time data analysis, fault detection, and analysis of inconsistencies in energy usage or expected HVAC system performance.  In many ways, LEED v4 has split the previous version’s M&V credit into two separate credits:  a credit for Advanced Energy Metering and a credit for MBCx as an optional path within Enhanced Commissioning.  Advanced Energy Metering requires the long-term trending, storage, and reporting of energy data for the all significant energy end uses within the building.  And while there are still many aspects similar to the M&V Planning phase, MBCx builds upon the focus on a design vs. operational energy comparison and corrective actions within M&V.  The MBCx credit includes the following additional criteria to be incorporated into the commissioning plan:

  • Specification of fault diagnostics or predictive algorithms for tracked points and metered values
  • Elements used to evaluate performance, including:
    • Conflicts between systems, such as simultaneous heating and cooling
    • Out-of-sequence operation of system components
    • Unexpected energy usage profiles
  • Ongoing operator and occupant training to prevent training
  • Planning ongoing monitoring device calibration to maintain performance
  • Frequency of analysis during first year of occupancy (at least quarterly)

USGBC correctly notes that, like the requirements for the LEED v3 M&V credit, MBCx is most cost effective when the metering, trending, and software requirements are included as part of the initial design and construction of a facility.   In summary, though the U.S. design and construction market was just on the verge of having wider acceptance of the IPMVP measurement and verification process, we are excited that the “spirit” of M&V lives on within LEED v4, albeit in two separate credits for advanced energy metering and Monitoring-Based Cx.