Page 204 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

182 Cha pte r F o u r

Special Circumstances and Exemplary Performance
Environmental attributes which are associated with the green power purchased cannot
be sold; they must be retained or retired. EAc6 has been designated as a construction
phase submittal, mainly because the utility contracts are usually not fully developed
until construction is nearly complete. If there are special circumstances for these credits,
a narrative must be submitted describing these circumstances.
In LEED 2.2, exemplary performance (EP) credit can be achieved by doubling the
requirement, either by doubling the amount of green electricity purchased to 70 percent
or by doubling the length of the contract to 4 years. In LEED 2009, this EP point is
awarded if 70 percent of the power is purchased from renewable sources. No mention
is made of extending the contract.

4.7 Discussion and Overview
The Energy and Atmosphere category seeks to reduce energy usage and the impacts of
energy usage on the environment. There are also additional comments which can be
made about the multiple benefits or effects of some of the measures used to obtain these
goals. Two examples relate to the promotion of on-site renewable energy sources and to
the location of the “breathing zone” within the interior spaces. Also, it might be useful
to address the use of hydrogen fuel cells and how that may fit in with the energy goals.
These are briefly discussed in the following sections.
On-Site Renewable Energy As previously discussed, EAc1, EAc2, and EAc6 all seek to
reduce the use of nonrenewable energy sources for both environmental and economic
reasons. Combined, the three credit subcategories give extra credit if on-site renewable
energy sources are used in this reduction. There are many reasons for this, including the
reliability of the overall power options when there are multiple sources, the importance
of distributing the use of energy sources so that they are not as concentrated and
therefore do not have such large, concentrated impacts on the environment in only a
few areas, and security issues in the energy network. Not only are there points available
in EAc2 for on-site renewable energy sources, but also use of these on-site sources
makes it possible to earn more points in EAc1 Option 1 and to reach the 35 percent
threshold in EAc6 for the same building energy needs.
For example, let us look at new building project X using LEED 2009, where the
project has equal cost values of electrical and natural gas needs. In the proposed design
if both the electrical and natural gas loads are reduced 22 percent from the baseline
design and there is no on-site renewable electricity production, then six points may be
earned based on EAc1 Option 1 as shown in Eq. (4.7.1).
⎛ PBP⎞
AECS = 100 × 1 − BBP⎠ ⎟ = 22 (4.7.1)
⎜
⎝
So PBP/BBP is 0.78, but since PBP equals PDEM less the REC, and REC is zero, then
PDEM/BBP is 0.78.
Let us then hypothetically reevaluate the situation if 24 percent of the electrical needs
(12 percent of the total cost value of the total project energy needs or REC = 0.12PDEM)
can be generated by renewable sources on-site. Then the following two equations apply:
⎛ PDEM REC⎞
⎜
.
AECS = 100 × 1 − BBP + BBP⎠ ⎟ = 31 4 (4.7.2)
⎝