ASHRAE Journal - March 2021 - 58

TECHNICAL FEATURE

[17.5 W/m2]), medium (1 W/ft2 [10.75 W/m2]) and
TABLE 2 Summary of reported EPD in previous studies.
low use (0.76 W/ft2 [8.2 W/m2]). While many
EPD RANGE
SOURCE
DATA SOURCE
BUILDING TYPE
(W/FT 2)
other studies provided detailed investigations of
Abushakra, et al.4 0.18 - 0.66
Submetered Receptacle Loads Commercial Office
plug load use in office buildings,9 - 12 they gener0.67 - 1.3
Submetered Receptacle Loads Academic Building
Lamano, et al.22
ally indicated that use patterns and EPDs showed
9
significant differences, even between tenants of
0.56
Submetered Receptacle Loads Commercial Office
Sheppy, et al.
the same office building. Masoso and Grobler12
Equipment Inventory and
0.93
Metzeger, et al.10
Assumptions on Power Use Commercial Office
also showed that more energy is used during
Srinivasan, et al.15
nonworking hours (56%), demonstrating poten* Without Computers: 0.25 - 0.85 Equipment Inventory and Power
K - 12 School
Use Data from Previous Studies
tial energy waste that would not be accounted for
* With Computers:
1-2
during the design phase or in energy codes and
Equipment Inventory and
Wilkins and Hosni21
0.25 - 2
standards.
Assumptions on Power Use Commercial Office
Other studies focused on analyzing plug load use
Measured Power Use of Commercial Office
Safraz, et al.6 0.34 - 1.53
Individual Equipment
in residential buildings. Johnson and Beausoleil8
0.76 - 1.6
Submetered Receptacle Loads Commercial Office
Harris and Higgins
Morrison13 analyzed the power draw of different
11
0.8, ±0.28
Submetered Receptacle Loads Commercial Office
Ward, et al.
appliances in 23 houses in Ottawa and demonstrated wide variability in non-HVAC power
0.41 - 1.3
Submetered Receptacle Loads Commercial Office
Bennet, et al.7
consumption between them. In a different study,
George and Swan14 analyzed appliances, lighting and
demonstrated the significant role of occupant behavior.
plug load (ALP) profiles using smart meter data from 160
Overview of Previous Work
houses in Nova Scotia over three years. They compared
Changes in building use patterns, space use and the
their results to the data set introduced in Johnson and
Beausoleil-Morrison13 and found the average hourly ALP types of equipment used in today's work spaces sugload profile for both data sets was remarkably similar;
gest that existing schedules are not representative of
dropping to around 40% at nighttime.
current use profiles. Duarte, et al.,17 showed that using
schedules based on measured data versus default
However, both trends showed a mismatch with both
ASHRAE schedules can change simulation results
the default schedule for aggregated internal heat gain
by as much as 39%. Similarly, Parker, et al.,18 found
loads in low-rise residential buildings in the Canadian
that using default schedules underestimated heatNational Building Code (NBC) and plug load schedules
ing demand by approximately 10% and overestimated
specified for multiunit residential buildings in NECB,
which suggest they drop to around 30% and 20%, respec- cooling demand by 50%, compared to using schedules based on data from existing buildings. Sarfraz
tively, during nighttime periods.
and Bach6 also showed that the load factors for plug
A smaller number of studies investigated plug load
15
loads of several office equipment categories was 10%
use specifically in school buildings. Srinivasan, et al.,
established benchmark EPDs for K - 12 schools under
to 33% lower than those specified in energy codes and
two categories-classrooms with computers and classstandards.
rooms without computers-using data from 18 schools in
In general, the reviewed literature suggests nighttime
the United States. For classrooms with computers, plug
plug load use is usually around 40% to 50% of peak plug
load densities ranged from 1 W/ft2 to 2 W/ft2 (10.76 W/m2 load use depending on building type, much higher than
to 21.52 W/m2), while it ranged between 0.25 W/ft2 to
the percentage specified in NBC, NECB and ASHRAE
0.85 W/ft2 (2.69 W/m2 to 9.15 W/m2) for classrooms with- Standard 90.1. Previous studies also showed that dayout computers. Similarly, Ouf, et al.,16 analyzed plug
time plug load use (as a percentage of peak plug loads)
load use in Manitoba school buildings and identified
is typically lower than NECB and ASHRAE Standard 90.1
hourly plug load use patterns, which varied considerassumptions. The effect of these variations on code comably compared to NECB schedules. They specifically
pliance or achieving net zero energy performance tarhighlighted variations between classrooms of similar
gets should be quantified to provide recommendations
characteristics, especially during nighttime, which
for potential code changes.
58

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