ASHRAE Journal - February 2011 - 86

commissioning

capturing the Potential
By Evan mills, Ph.D.

he emerging practice of building commissioning is a particularly potent means of increasing energy efficiency. Although commission-

ing has earned increased recognition in recent years—even a toehold in Wikipedia—it remains an enigmatic practice whose visibility considerably lags its potential.
Quality assurance and optimization are essential elements of any serious technological endeavor, including efforts to improve energy efficiency. Commissioning is an important tool in this respect. The aim of commissioning new buildings is to ensure that they deliver—if not exceed—the performance and energy savings promised by their design. When applied to existing buildings, one-time or repeated commissioning (often called retrocommissioning) identifies the almost inevitable drift in energy performance and puts the building back on course, often surpassing the original design intent. In both contexts, commissioning is a systematic, forensic approach to improving performance, rather than a discrete technology. Specific deficiencies identified and corrected through the commissioning process include problems such as simultaneous heating and cooling, inefficient thermal distribution layout, miscalibrated or otherwise malfunctioning energy management controls and sensors, defeated efficiency features (e.g., variable speed drives locked at full speed), leaky air-distribution systems, inappropriate setpoints and control sequences, and oversized equipment. These kinds of problems collectively waste several tens of billions of dollars in energy each year
86 ASHRAE Journal

in the U.S. alone, while compromising occupant comfort, health, and safety. In an ideal world, these issues would be caught during the original design or corrected by routine operations and maintenance, but that is all too rare in practice. Energy-wasting deficiencies are often invisible to the casual observer, and unfortunately also to building designers, operators, owners, and all but the most attuned engineers. Commissioning can reduce the carbon footprint of unremarkable buildings, or ensure the success of ones deliberately designed to push the limits of efficiency. Uncertainties about cost and costeffectiveness are a key barrier to the growth of the commissioning industry. Building owners understandably ask why they need to pay “extra” for remediation of less-than-best practices. Program designers, utility regulators, and other policymakers must all justify investments in commissioning. In an effort to provide better information to all players, the Lawrence Berkeley National Laboratory (LBNL) has assembled the world’s largest compilation and meta-analysis of commissioning experience in actual commercial buildings. The database has grown to 643 buildings (all located in the U.S., and spanning 26 states). Projects represent 100 million ft2
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(9 290 300 m2) of floorspace, $43 million in commissioning expenditures, and the work of 37 commissioning providers. The recorded cases of new-construction commissioning took place in buildings representing $2.2 billion in total construction costs. The costs include labor and materials for external commissioning agents, plus other trades and supporting in-house staff, and are limited to commissioning activities targeting energy savings, as distinct from other systems such as safety and security. The results are compelling. The median cost to deliver commissioning was $0.30/ ft2 ($3/m2) (in 2009 dollars) for existing buildings and $1.16/ft2 ($12/m2) for new construction (or 0.4% of the overall construction cost). More than 10,000 specific deficiencies were identified across one-third of the sample for which data were available. Correcting these problems resulted in 16% median whole-building energy savings in existing buildings and 13% in new construction, with payback times of 1.1 years and 4.2 years, respectively. Median benefit-cost ratios of 4.5 and 1.1, and cash-on-cash returns (a common statistic used in the real estate industry) of 91% and 23% were achieved. Projects with a relatively thorough approach to commissioning (e.g., incorporating benchmarking, design intent documentation, construction observation, functional testing, acceptance testing, operator training, and calibrated simulation) attained nearly twice the overall median level of savings and five-times the savings of the least-thorough projects. It is noteworthy that virtually all existingbuilding projects were cost-effective by each metric (e.g., paybacks of 0.4 years for the upper quartile and 2.4 years for the lower quartile), as were the majority
February 2011

ASHRAE Journal - February 2011

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