ASHRAE Journal - November 2019 - 20

TECHNICAL FEATURE

on daytime and nighttime
demand for one of their highperformance office buildings.5
By using these in conjunction
with PEI ranges, modelers can
easily set targets for buildings
during both design and operation phases. An PEI of 1.0 ultimately represents a building
with no unregulated energy
use-a building that could be
wholly passively conditioned
and lit-our version of energy
nirvana.

Building Performance Factor
Alignment

TABLE 5 EUI and PEI means for medium office, large office, multifamily, and secondary school cases.
MEAN

BUILDING TYPE

EUI Medium
(kBtu/yr·gft2)
Office

BUILDING TYPE

Large
Office

MultiFamily

Secondary
School

PEI

Medium
Office

Large
Office

MultiFamily

Secondary
School

Baseline

37.1

75.3

53.0

51.6

Baseline

2.7

1.9

4.0

3.7

50%
Process

32.4

70.4

47.7

45.2

50%
Process

3.8

2.0

6.2

6.2

25%
Process

30.5

68.1

45.4

41.7

25%
Process

5.2

2.0

9.5

10.5

150%
Process

42.3

80.5

59.0

57.9

150%
Process

2.2

1.7

3.1

2.8

50%
Occupancy

37.3

75.4

53.3

47.9

50%
Occupancy

2.7

1.8

4.0

3.4

25%
Occupancy

37.4

75.4

54.4

46.5

25%
Occupancy

2.7

1.8

4.0

3.3

50%
Combined

29.9

69.7

44.4

38.4

50%
Combined

3.5

1.9

5.8

5.2

25%
Combined

27.0

67.1

40.2

33.1

25%
Combined

4.6

2.0

8.4

8.3

The building performance
TABLE 6 EUI and PEI normalized values to baseline for medium office, large office, multifamily, and secondary school cases.
factor methodology was introNORMALIZED
BUILDING TYPE
BUILDING TYPE
duced within Addendum
EUI Medium Large Multi- Secondary
PEI Medium Large Multi- Secondary
BM to ASHRAE/IES Standard
(kBtu/yr·gft2)
Office Office family
School
Office Office family
School
90.1-2013, with the intent of
Baseline
100% 100% 100%
100%
Baseline
100% 100% 100%
100%
allowing for a stable baseline
50% Process
87%
93% 90%
79%
50%
141% 105% 155%
165%
Process
for performance-based compliance indexed to a ASHRAE/
25% Process
82%
90% 86%
73%
25%
196% 105% 238%
281%
Process
IES Standard 90.1-2004 level of
150% Process
114% 107% 111%
102%
150%
81%
89%
78%
76%
stringency.6 This approach sigProcess
nificantly reduces the challenge
50% Occupancy
100% 100% 101%
84%
50%
100%
95% 100%
92%
of energy simulation baseline
Occupancy
workflows that change with
25% Occupancy
101% 100% 103%
81%
25%
100%
95% 100%
89%
Occupancy
each new standard cycle.
50% Combined
81%
93% 84%
68%
50%
130% 100% 145%
143%
The BPF methodology allows
Combined
simple differential factors by
25% Combined
73%
89% 76%
58%
25%
174% 105% 210%
227%
building type and climate zone
Combined
to be updated as stringency
increases. A recent study7 shows the inherent difficulty
significantly depending on the process load density
in setting target EUIs using this methodology, because it
(0.25 W/ft2 [2.7 W/m2], 1 W/ft2 [10.76 W/m2], 5 W/ft2 [54
W/m2]).
uses a process load neutral approach. While normalized
The outcome-based compliance pathway in the
scales, like the zEPI,8 seek a simpler presentation of relative stringency of different standard versions, there is not 2015 International Green Construction Code (Section
a mechanism to scale EUI targets to accommodate varying 612) indicates a fixed source energy use intensity tarprocess loads.
get based on a building's use type and climate zone.
For example, normalized values (zEPI) for a medium
Compliance is demonstrated through actual measured
office prototype model in Climate Zone 3A are shown
utility data. A singular energy target value does not
in Table 7. The reference standard and the process load
address the significant impact of unregulated process
density are the primary variables. For the same stanenergy use differences or higher building occupant
dard stringency, the normalized energy use varies
density. Future outcome-based codes must address this
20

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