ASHRAE Journal - November 2019 - 22

TECHNICAL FEATURE

to be fair. Is it better for a building
TABLE 7 zEPI comparison for test cases for the medium office prototype in ASHRAE Climate Zone 3A with process load density of 0.25, 1, and 5 W/ft2. 6
to have a higher EUI, due to high
90.1-04
90.1-10
90.1-13
90.1-16
189.1-2014
2012
2015
occupant density, than one that has
DOE
BPF
BPF
BPF
OPT A
IGCC
IGCC
an artificially low EUI due to limzEPI
75
57
52
48
40
51
50
ited occupancy? The PEI factor may
2
70
55
48
46
37
49
47
Medium Office: 0.25 W/ft
be a way to adapt EUIs for a range of
2
94
79
73
70
55
71
70
Medium Office: 1 W/ft
process load intensity, which could
2
248
226
217
213
165
202
209
Medium
Office:
5
W/ft
also eventually address ventilation
rate variation. The worst outcome
of an outcome-based compliance pathway would be
Conclusion
This study presents pre-computed data that can be reffor occupants to reduce energy use at the detriment of
erenced by design and operations teams for benchmarkproductivity, through reduced ventilation, reduction
ing. The use of the PEI metric shows potential for unreguin compliance with ASHRAE Standard 55 for thermal
lated load optimization across climate zones and building
comfort, or through the elimination of specialized
types, when used in a complementary fashion to the EUI
equipment.
metric. We are considering additional sensitivity analyApplication
ses for office buildings, to inform its implementation in
PEI is applicable across the full building life-cycle,
outcome-based energy code compliance pathways.
including planning, design, commissioning, and operaAcknowledgment
tion phases.
Special thanks to the District of Columbia Department
* Planning: a PEI target can be set using the pre-comof Energy and Environment for its work on adoption of
puted values presented in Table 1. The PEI target would
the International Green Construction Code and an outbe less than these values.
come-based code compliance pathway. Their leadership
* Design: PEI may be easily calculated from whole
was a major inspiration for this research.
building energy simulation results and viewed in conjunction with EUI, either alone or as a multiplier (PEI ×
EUI = EI). An increasingly low PEI × EUI value represents References
1. Chang, R. 2014. "Landmark resurrection." High-Performing Buildings.
a design that has been optimized for both regulated and
2. Avelar, V., Azevedo, D., French, A. 2012. "PUE: a
comprehensive examination of the metric." The Green Grid.
unregulated energy.
3. Chang, R. 2016. "Energy utilization effectiveness (EUE): a
* Commissioning/operations: tracking real-time PEI
new metric for commercial building energy use characterization."
may allow optimization of system operation for imASHRAE Winter Conference.
4. Sarfraz, O., C. Bach, C. Wilkins. 2018. "Plug load design
proved part-load performance. Development of a meterfactors." ASHRAE Journal (1).
ing strategy early in design is critical. Electrical system
5. Lobato, C., S. Pless, M. Sheppy, P. Torcellini. 2011. "Reducing
design should consider how loads are best grouped to
plug and process loads for a large scale, low energy office building."
ASHRAE Winter Conference.
simplify metering at panelboards. Non-intrusive load
6. Rosenberg, M., Hart R., Developing Performance Cost Targets
9
monitoring (NILM) methodologies can further provide
for ASHRAE Standard 90.1 Appendix G - Performance Rating
a mechanism to capture process loads.
Method, PNNL-25202, Pacific Northwest National Laboratory,
Richland, Washington, February 2016.
* Outcome-based code frameworks: a building's
7. Chang, R. 2017. "Impact of Process Load on Commercial Office
target EUI may be viewed in conjunction with PEI, where Energy Performance." ASHRAE Building Performance Analysis
measured process load energy × PEI can be used to set
Conference (Seminar 9).
8. New Buildings Institute, https://newbuildings.org/code_
adjusted EUI targets.
policy/zepi/, 2018.
* Airflow-driven building types: building types, such
9. Baechler, MC, H Hao. 2016. "Business case for nonintrusive load
as hospitals, restaurants, and laboratories may still utimonitoring." PNNL- 25425, Pacific Northwest National Laboratory.
lize the PEI methodology as an additional benchmarkBibliography
ing point. Additional research on an index adapted to
Zhao, J, Yun, R., Lasternas, B., Wang, H., Lam, K.P., Aziz, A.,
process airflow requirements beyond ASHRAE Standard Loftness, V., Occupant Behavior and Schedule Prediction Based on
Office Appliance Energy Consumption Data Mining, CISBAT, 2013.
62.1 requirements, may be beneficial.
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ASHRAE Journal - November 2019

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