Evaluating How Effectively Energy Is Used

  May 24, 2016

The effectiveness of the energy used to provide for the fundamental purpose of the building can be evaluated by establishing a “Figure of Merit” (FOM), which combines energy use and occupant response data. An example of such an FOM is the ratio of the EUI to the percentage of occupants whose average response is that the overall indoor environment in their workplaces is “acceptable” (i.e., OA).

Another similar example is the ratio of the EUI to the percentage of occupants whose average response is that the temperature (or illumination level, sound level, or odor perception level) at their workplaces is acceptable. Of these FOMs, the overall “Acceptability Index Value” (AIV), defined as EUI/OA, offers an opportunity to increase the sensitivity of building performance metrics by evaluating the effectiveness of the annual energy used per percentage of overall occupant acceptability results. A lower AIV indicates that energy is being used more effectively to achieve occupant satisfaction. Similar and incrementally more sensitive AIVs can also be derived for other specific attributes (e.g., thermal, lighting, air quality, and acoustics).

The National Center for Energy Management and Building Technologies (NCEMBT) conducted original research in which energy consumption, building materials and system data, and human response and occupant performance data were obtained during occupied conditions. A total of 30 buildings were studied, 10 of which were “normative” office buildings, 10 “high-performance” office buildings, and 10 “normative” school buildings.

In addition, the National Institute of Building Sciences (NIBS) reported on post-occupancy evaluations of four U.S. federal courthouses constructed, expanded, or modernized between 1998 and 2008. Two of these were LEED Gold: one new construction (NC), and one existing building (EB pilot). Concurrent data were acquired for energy consumption and occupant responses, which were obtained by a standardized survey questionnaire. The occupant responses were in the “affective-environmental domain,” as defined in the NIBS evaluation protocol. The NIBS reports also include analyses of building system performance.

Data from the NCEMBT and NIBS reports, which were validated for complete data sets, were transformed to AIVs. Click here to see an overview of the characteristics of validated data for five buildings in the NCEMBT data set and two buildings from the NIBS data set.

This quick read is from Davor Novosel, the chief technology officer for the National Energy Management Institute Committee (NEMIC), and James E. Woods, Ph.D., P.E., who has more than 50 years experience in energy and environmental analyses and who has been responsible for more than 30 research projects and 250 investigations related to indoor environmental quality, energy use, and human responses. Read more from them about energy and occupant performance.


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