Measurement and Verification for Optimum Building Performance

by Shaun May, EIT and Jeff Yirak, P.E., CPMP, LEED AP BD+C, O+M

This article is part of Wood Harbinger’s newsletter series.

Measurement and Verification (M&V) is a critical practice in assuring optimal building performance, but it is often overlooked. Too often buildings are completed with a, “Tah-dah! It’s working!” but few ever take a deeper, quantitative look at how it is working. In fact, many buildings operate for years and years without check-ups, efficiency analyses, or performance reviews. It’s time to change this trend! Building design effort is wasted and hopes for energy and cost savings won’t be fulfilled if the structure and equipment are not installed, balanced, and operated correctly, at turnover and throughout the life of the facility. Performance measurement and data logging will establish the real-world baseline operation of a facility, and ongoing measurement will ensure the health of the facility for its full life.

Flavors of M&V

The International Performance Measurement and Verification Protocol (IPMVP) provides four measurement and verification options. These are primarily focused on the measurement and verification of targeted energy improvement measures, but can be adapted to any new building project.

The first strategy, Partially Measured Retrofit Isolation, measures a portion of an energy-consuming system through the use of subsystem metering, or submeters, and assumes that usage is constant during that system’s operation. This is an effective way of isolating or further identifying a particular usage, such as electricity used for lighting, which has a continuous level of energy consumption during operation. This strategy is effective, but relies on some assumptions, such as occupancy schedules, that may deviate from the real-world use of the building, making the calculated measurements inaccurate.

The second strategy is Retrofit Isolation, which, as in the last method, uses submeters to identify subsystem energy consumption. It differs by continuously recording the dynamic energy consumption during real-time. This is more appropriate for a varying energy consumption system, such as a gas boiler or variable-speed fan. This strategy is effective in monitoring a high degree of specific energy consumption.

The third strategy is Whole Facility Metering, in which energy consumption is measured at the points of entry for the different utilities. This is a high-level view of energy consumption within a building, but may be appropriate for a building that is operating within a portfolio of similar buildings to monitor for outliers that need more specific attention. This is a good pairing with the second strategy for monitoring energy consumption within a building.

The fourth strategy is to employ a Calibrated Simulation of energy usage. In new designs, this may be an energy model or energy life cycle cost analysis. These models are frequently based on assumed values for insulation, energy consumption, and occupancy. The measurement exercise is a valuable way of fine-tuning the simulation, but the high reliance on assumptions may make this strategy less accurate.

Direct measurement of point of use energy consumption is the most detailed, useful, and reliable way to perform a measurement and verification project.

Preparing for Measurement

Our experience shows that one of the first challenges with collecting measurements lies with the measuring itself. The designers must incorporate the measurement tools and meters, either manually-read or automatically reporting to the central control system, into the contract documents. We recommend the latter, where automatic measurement not only relieves the facilities staff from record keeping and data entry, but also serves a secondary benefit during troubleshooting, where real-time, continuous measurement may be helpful.

A permanent performance monitoring system, like a Building Automation System (BAS), is a sure bet for optimizing building performance. A building-wide system such as this is a highly customizable computer system built with nearly any combination of controller inputs, outputs, and programming logic. The BAS’s customizability leads to great flexibility on the part of design engineers to refine system operation and interactions. This is often a necessity with today’s highly efficient HVAC and lighting systems, which require sophisticated control schemes, such as daytime temperature or ventilation setbacks as well as daylighting integration to reduce energy consumption. It also makes it a very effective hub for measurement and verification of system functions, as it can control equipment sequences and schedules, gather metered data, trend performance, alert facilities staff of equipment failures, and can automatically analyze and optimize equipment operation.

A BAS can also integrate auxiliary equipment, including sensors, meters (water, gas, and electrical current flow), actuators, starters, controllers, and more. This is a beneficial aspect, because sub-metering plug-loads, lighting, heating, cooling, ventilation, water, and process equipment enables building operators to identify which systems consume the most energy and therefore may be targeted for tuning. These meters may serve no other purpose but to facilitate the energy measurement and verification. The commissioning design review focuses on the operability of the building to ensure that these appurtenances are included in the design for use during measurement and verification.

Specifying and installing monitoring equipment will add a small percentage to the initial system costs in new construction (1% or less) in order to save money over the long run. Thoroughly integrating these base components with the BAS empowers the operator to efficiently optimize system operation.

Establish a Benchmark with Trending

Measurement and verification data reporting begins with establishing a benchmark—a picture of how the building is currently running. To establish a benchmark, the building operator sets the building systems to operate normally and then records energy consumption, equipment commands, and statuses over a set time period. Commissioning providers call this measurement process “trending,” as it establishes the trend of what will be considered normal system performance.

Since a building’s energy use profile changes throughout the year, seasonal trending is recommended to capture building operation during the separate heating and cooling building seasons. For this reason, initial benchmarking over the course of the entire year of building operation proves valuable. Check out Jeff’s seasonal trending article to learn more about this practice.

This trending process can be done for a new building and should also be completed periodically throughout a building’s life. The operational trends are then compared against the building design documents to verify whether the building is operating per design intent or if it is out of alignment. Trending may confirm that operation is per design. If so, that’s great! You have documented data that all is well and a baseline of comparison in the future, should you find the building operating differently later on.

Trending may also reveal inconsistencies that otherwise might stay hidden, such as errors in control sequences, equipment malfunctions, control system operational overrides, equipment schedule issues, and energy waste. Poor building operation doesn’t mean there must be some deficiency in the equipment or systems. For existing buildings, it can be (and often is) the result of unanticipated usage, inefficient operation, or deferred maintenance. These types of things can often be fixed by retuning systems, with controls adjustments, equipment, regular maintenance, or a reevaluation of building usage.

Maintaining Operations

With a benchmark established, any necessary retuning complete, and a permanent monitoring systems in place, building systems are poised for optimum operation, and just need to be upheld. This is more difficult than it sounds. When a building is not consistently monitored and tuned for efficiency, systems tend to wander further and further away from their optimum operating ranges.

A digital dashboard can serve as a useful communication tool for both facilities staff and building occupants, helping keep energy consumption and resources use top of mind. The BAS can be used to monitor and verify correct equipment operation and guide proper maintenance. Equipment failures and/or temporary repairs can compromise system efficiency and degrade equipment life, which increases operating costs over the long term. Analytics software built into the BAS can help identify such issues.

Accessible operation and maintenance literature is a critical tool in maintaining optimized system performance. With high performance buildings using comprehensive but complex controls systems, a systems manual is a helpful tool, communicating the complete picture of the components of the facility from a systems perspective. It allows facilities staff to see the comprehensive interaction of components in a system and the inter-system activities and reactions that make up building performance. With a solid understanding of operations and maintenance procedures coupled with data from the BAS and an easy-to-read dashboard, maintaining optimum operations over the life of the facilities becomes a manageable task.

Ongoing Commissioning

Ongoing commissioning is recommended to regularly check performance against benchmarks and track the historical energy performance of the building. Think of it like an annual check-up at the doctor’s office; an outside perspective to confirm that everything is operating as it should is a beneficial practice for preventing problems from getting worse, if they exist.

Recommissioning the building systems, either on a regularly occurring schedule (every 3 to 5 years is typical), or if building performance degrades, or if the building occupancy or usage changes significantly, is recommended by the Building Commissioning Association to ensure that systems are operating at peak efficiency. This process also generates opportunities to integrate new technologies to improve performance.

Measurement and verification may seem like an obvious procedure, but it can also seem a simple thing to forego, if time and money are tight, as they often are. But a little up front can save unforeseen problems or costs down the road, so we encourage you to give measurement and verification a top priority! Tenant satisfaction is improved, building energy consumption is reduced, and equipment lasts longer as a result of ongoing measurement and verification.

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