Commissioning

Figure 2. In this photo, the sensor intended for sensing and

"harvesting" daylight by dimming the electric lighting, is installed

incorrectly and always "sees" the electric light, never allowing it to

sense and take advantage of the dimming capability of the system.

Economics

Commissioning offers highly compelling engineering economics. This arises largely because commissioning focuses on operational optimization rather than capital improvements. Buildings included in a national database of 100 million square feet of floor area in existing buildings attained median whole-building energy savings of 16% at a cost of approximately $0.30/sq, achieving median payback times of approximately one year, respectively. The upper quartile of buildings save in excess of 30%, and even the lowest quartile saves almost 10%. These value ranges could be applied as reference points in benchmarking commissioning costs. The more thorough the commissioning process, the greater the savings. Contrary to a common perception, cost-effectiveness is often achieved even in smaller buildings. In new construction, commissioning routinely pays for itself via capital cost savings arising from equipment right-sizing and avoided construction defects. In many cases, these savings far surpass the cost of commissioning.

There is a second layer of value that is arguably even more substantial. Commissioning manages performance risk, and thus financial risk (Figure 3). Capturing this value requires vigilance over time and tracking. Energy management and control systems have been used in tight coordination with commissioning, often called monitoring-based commissioning. This can detect certain faults [see Diagnostics section], as well as tracking savings persistence. On the one hand, if buildings are unattended, energy use will rise as systems come out of "tune". At the other extreme, vigilance can deepen savings as new opportunities are identified and emerging defects corrected. That said, visual inspection suffices for many commissioning opportunities such as misplaced sensors, malfunctioning dampers, or ductwork or piping layouts with excessive pressure drop.

Figure 3. Conceptual illustration of the potential for recurring

commissioning to deepen and ensure the persistence

of energy savings and other benefits.

Other considerations

An additional tier of benefits transcend conventional engineering economics. These benefits manifest in multiple ways, including enhanced indoor air quality, reduced noise, improved equipment service life, fewer change orders, and averted contractor call backs and litigation. By virtue of proactively detecting and correcting deficiencies, insurance companies have concluded that commissioning would have averted liability claims associated with construction projects. Commissioning ensures attainment of project goals, and intrinsically brings more cohesion to the in-house and external teams working on a project.

These co-benefits are often captured as a byproduct of the commissioning process (Figure 4). More proactive commissioning could focus deliberately on detecting and correcting the causes of important non-energy problems. For example, improving and ensuring indoor environmental quality could be an organizing principal for focused commissioning exercises. Here, emphasis would be placed on evaluating surface temperatures in a space, air movement and moisture content, as well as key aspects of HVAC systems such as morning start-up sequences or sensor location and calibration. Similarly in the case of visual comfort, focused commissioning of illuminance levels and distribution could be done to determine whether changes in space uses or activities may dictate adjustments in illumination. Occupant changes in spaces (window treatments, task lighting, changes in decoration) may also call for adjustments in lighting.