ASHRAE Journal - November 2019 - 13

TECHNICAL FEATURE

commercial buildings. The intent is to focus on annualized energy use, rather than power demand.

Total Building Energy Use
Regulated by ASHRAE/IES Standard 90.1 (Enclosure, Lighting, Service
Hot Water, HVAC) + Process Energy

Ö
Total Process Energy Use
Typical Items: Computers, Printing Equipment, Machine Tools, Medical
Equipment, Specialty Lighting

concept using parametric energy simulation using
the ASHRAE/IES Standard 90.1-2013 DOE Commercial
Reference Building Models and EnergyPlus v8.8. Our
intent was to observe correlations between PEI and EUI
and determine a reasonable range for PEI across four
major building types: medium ofﬁce, large ofﬁce, secondary school, and high-rise residential. We created
eight permutations from the standard models:
* Process Load 1 (P1): 25% of reference model
* Process Load 2 (P2): 50% of reference model
* Process Load 3 (P3): 150% of reference model
* Occupancy Load (O1): 25% of reference model, no
ventilation rate adjustment
* Occupancy Load 2 (O2): 50% of reference model, no
ventilation rate adjustment
* Combination 1 (C1): Occupancy, ventilation, and
process load at 25% of reference model
* Combination 2 (C2): Occupancy, ventilation, and
process load at 50% of reference model.
Cases P1, P2, and P3 allow us to evaluate the impact
of process load density on PEI and EUI. With a baseline
process load density of 1 W/ft2 (10.76 W/m2), permutations at 0.25 (2.7), 0.50 (5.4), and 1.5 W/ft2 (15.1 W/m2)

The PEI can be used to start setting targets for a range
of buildings, with an emphasis on ofﬁce buildings. The
PEI metric is intended to capture demand reduction
measures; on-site renewable energy production would
be excluded from the metric.
Initial research utilizing pre-computed results
from the DOE Commercial Prototype Buildings (pre1980, post-1980, 90.1-2004) showed lower PEIs were
evident for newer buildings.3 As energy standards
became more stringent, the ratio of unregulated
process energy use to total energy use increased in
these models, as process energy
TABLE 1 Comparison of EUI and PEI based on ASHRAE's High Performing Buildings (HPB) magazine case studies.
This data represents a mix of both measured and simulation data.
was ﬁxed. In reality, technology
PROJECT
CLIMATE ZONE
BUILDING TYPE AREA (FT 2)
EUI (KBTU/YR· GFT 2) PEI
improvements have also allowed
unregulated process energy use to
Wayne Aspinall Federal Building
5B
Medium Ofﬁce
41,562
21 2.9
(HPB Summer 2014)
decrease.
3C
Museum
190,000
50 2.9
Exploratorium
A sample of past case studies was
(HPB Spring 2015)
evaluated to contrast EUI to PEI. This
1A
Stand-Alone
4,620
36.6 3.3
PNC Bank
is not intended to be an exhaustive
(HPB Winter 2015)
Retail
evaluation, given the coarse nature
4C Higher Education
13,500
33.2 2.4
Portland Community College-
Newberg Center
of the data used, but is intended
(HPB Winter 2015)
to generate discussion about the
4C
Large Ofﬁce
188,587
25.7 4.1
Federal Center 1202
relationship between process loads
(HPB Fall 2014)
and overall building energy use for
4C
Higher
26,900
18.2 1.9
St. Martens University-
Education
Cebula Hall
buildings at the forefront of energy
(HPB Spring 2014)
use efﬁciency. In these case stud6A
Medium Ofﬁce/
34,000
41.8 15.5
Gateway West
ies, the calculated PEI was typically
(HPB Winter 2013)
Warehouse
under 3.0. The sample set primarily
5A
Higher
13,600
32.9 4.5
Oberlin College-
Education
Lewis Environmental Center
included ofﬁce buildings and K-12
(HPB Winter 2011)
schools, mostly in ASHRAE Climate
5B
Large Ofﬁce/
220,000
35.4 1.8
NREL Research Support Facility
Zones 5B or 4C (Table 1).
(HPB Fall 2012)
Data Center
Gettysburg Museum

Test Cases

5A

Museum

140,000

228

2.6

(HPB Summer 2011)

We further explored the PEI
N O V E M B E R 2 0 19

ashrae.org

ASHRAE JOURNAL

13
http://www.ashrae.org
ASHRAE Journal - November 2019

Table of Contents for the Digital Edition of ASHRAE Journal - November 2019
