Page 183 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

LEED Ener gy and Atmospher e 161

In summary, Option 1 is calculation-intensive. There are a total of five simulations that
need to be performed, including one of the design case and four of the baseline case,
one in each of the four orthogonal orientations. The four baseline case orientations are
then averaged to obtain the baseline.
The annual energy percent cost savings (AECS) can be calculated based on a proposed
building performance (PBP) and the base building performance (BBP). The use of on-site
renewable energy as calculated as the REC may increase the points obtained from
Option 1 of this credit, as the REC is used as a reduction in the calculation of the PBP ,
offsetting this amount of energy use as if it were free. The PBP is calculated as follows:
PBP = PDEM − REC (4.1.1)

The annual energy percent cost savings (AECS) as used in the point determinations for
EAc1 can then be calculated from either of the following two equations:
⎛ PBP⎞
AECS = 100 1 − BBP⎠ ⎟ (4.1.2)
⎜
⎝
or alternatively

⎛ PDEM REC⎞
AECS = 100 1 − BBP + BBP⎠ ⎟ (4.1.3)
⎜
⎝
Equation (4.1.3) shows the positive impact that using on-site renewable energy has on
the point potential for EAc1, when using Option 1.
LEED-NC 2.2 and 2009 include both regulated and process loads in assessing
Option 1. Since much of the energy efficiency focus is on regulated loads, it is also
useful to be able to segregate out these two parts of the energy loads for both the base
building and the proposed design. This is readily done by defining BBPR and BBPP as
the regulated BBP load and the process BBP load, respectively, and by defining PDEMR
and PDEMP as the regulated PDEM load and the process PDEM load, respectively. By
definition,

BBP = BBPR + BBPP (4.1.4)

and
PDEM = PDEMR + PDEMP (4.1.5)

It is usually easier to assess the regulated loads (BBPR and PDEMR) in the evaluations,
as these are the ones most appropriately considered for energy efficiency measures. In
most cases, the base process load is considered to be 25 percent of the base and does not
change from the base to the proposed design. When this is the case, Eqs. (4.1.4) and
(4.1.5) can be simplified to the following:

BBP = BBPR/0.75 base process is 25% of base load (4.1.6)

and
PDEM = PDEMR + BBPR/3 base process is 25% of base load and
(4.1.7)
does not change in design