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180 Cha pte r F o u r
portion of Eq. (4.2.1) and does not include cost rates.] The GFA in Eq. (4.6.1) is the gross
floor area of the building as defined in Chap. 2. If the project is made up of several
buildings or building portions with different uses as listed in Table 4.2.3, then the
commercial building energy consumptions (CBECSE ) for electricity should be separately
j
analyzed for each portion, multiplied by the gross floor area in that building portion,
and summed to obtain the BAEE.
BAEE = (CBECSE )(GFA) if EAc1 Option 1 is not sought (4.6.1)
j
On the other hand, the basis for the electric usage when EAc1 Option 1 is sought
is a portion of the Proposed Building Performance (PBP) as previously calculated in
Eq. (4.1.1). In LEED-NC 2.1, a point was earned in EAc6 if the green power purchased
was at least 50 percent of the difference between all regulated electricity loads and the
electricity provided by on-site renewal energy sources. For this earlier version, the
EAc1 calculations were all based on regulated loads. In LEED-NC 2.2, the calculations
for EAc1 Option 1 are based on both regulated and nonregulated loads for which the
nonregulated loads are assumed to be approximately 25 percent of the regulated
loads. (Nonregulated loads are sometimes referred to as process loads.) Therefore, the
threshold in LEED-NC 2.2 has been reduced to 35 percent to take into account the
calculation changes. In LEED-NC 2.1, the modeled energy electrical use was further
modified to account for on-site renewable energy production. Keeping this modification
in LEED-NC 2.2 and carried forward to LEED 2009, the author has interpreted that the
calculation appropriate for the first compliance path (EAc1 Option 1) should again
include this reduction in the denominator of the on-site renewable energy, so that
the percent green power purchased is truly only the percent of the demand from the
off-site grid.
Keeping this modification in mind, let PBE (proposed building electrical performance)
be the electrical energy portion of the PBP as defined in EAc1 Option 1. If PDEE is the
proposed design electrical energy portion (in electrical usage units) as given from the
proposed design energy model (PDEM), then the PBE is the difference in the electrical
usage portion of the PDEM in units of electrical power per year (PDEE) and the electrical
portion of the annual on-site renewable energy (REC) in units of electrical power per
year (REE).
PBE = PDEE − REE if EAc1 Option 1 is sought (4.6.2)
Using the annual amount of green electricity (GE) purchased or traded from off-site,
and the definitions for proposed building energy needs, PBE and BAEE, based on the
EAc1 Option 1 compliance pathway and other energy calculation pathways, respectively,
the percent green electricity (PGE) can be calculated for each as
GE
PGEPB = 100 × if EAc1 Option 1 is sought (4.6.3)
PBE
or alternatively
GE
PGEPB = 100 × if EAc1 Option 1 is sought (4.6.4)
−
PDEE REE