[BLDG-SIM] USGBC response on questions about process loads for LEED 2.2

[Brian Thornton]

The USGBC responded to a CIR submitted through our local LEED Consultant,
Brightworks, and Gwen Fuertes of the USGBC OK'd posting this to BLDG-SIM.
Replies are interspersed in the questions as USGBC Response, in yellow
highlight, but the yellow may not survive BLDG-SIM posting.  USGBC had not
confirmed if this would be posted as a CIR ruling.  For specific projects,
you may still want to get separate rulings if still unsure, or don't like
the impact of the responses on your project. .    

 

 

RE       EAc1 Process Loads Rules for LEED NC 2.2

DT       7 March 2007

 

There is a lot of uncertainty about the handling of EAc1 process loads under
LEED 2.2.  An all-day intermittent dialogue on BLDG-SIM, the energy user's
group, resulted in more questions and no consensus on how to handle the
following provisions in the Reference Guide.  The dialogue also did not show
that anyone had received a ruling.  We request clarification on the
questions listed below, and suggest that an administrative ruling be issued
to clarify this for the whole analyst community. 

 

"The default process energy cost is 25% of the total energy cost for the
Baseline building. For buildings where the process energy cost is less than
25% of the baseline building energy cost, the LEED submittal must include
supporting documentation substantiating that process energy inputs are
appropriate. "
...
"For EA Credit 1, process loads shall be identical for both the Baseline
building performance rating and for the Proposed building performance
rating. However, project teams may follow the Exceptional Calculation Method
(ASHRAE 90.1-2004 G2.5) to document measures that reduce process loads.
Documentation of process load energy savings shall include a list of the
assumptions made for both the base and proposed design, and theoretical or
empirical information supporting these assumptions. "

 

A series of questions resulted some of which are more clear than others, but
again did not have consensus understanding.

 

1)  To model the HVAC load for a project, all process loads must also be
modeled.  Under the modeling rules for NC 2.1 projects, all loads are
modeled and the process loads (non-regulated loads) are broken out of the
final reported energy and energy costs.  For all NC 2.2 projects, what
process loads get modeled apart from what process energy and energy cost
gets reported?  Should all process loads be modeled equivalent to the method
for modeling all non-regulated loads for NC 2.1 projects, regardless of the
25% default?

 

USGBC Staff response: All process loads get modeled. If the actual process
load is less than 25%, use the default (25%) or explain the actual load in
more detail. If the actual process load is more than 25%, use the actual
percentage.

 

2)  For all projects, is the reported process energy cost adjusted to reach
25% of baseline energy cost?  Is this adjusted to the same process energy
cost value for both the baseline and design if one of the two exceptions
listed in question 3 are not met?

 

USGBC Staff response: No; the reported process energy cost is not adjusted.

 

3)  Please confirm our understanding that two exceptions apply to 2), 1. as
noted, it is possible to model and report less than 25% of budget energy
cost for process in both the baseline and design, with design documentation,
and 2. the design may have lower process energy modeled and reported for
energy cost saving Exceptional Calculations. 

 

USGBC Staff response: For exception #1, it is possible to model and report
less than 25% of budget energy cost for process if this is justified and
explained fully.

 

4)  For projects with process energy loads that exceed 25% of baseline
energy cost due to design (such as lab buildings with high process loads),
do the energy and energy cost reported get reduced to be consistent with 25%
of the baseline energy cost while modeling the actual process energy uses?
Does the reduction to 25% of baseline energy cost apply to just the baseline
as some suggested, or to both the baseline and design if at all?  

 

USGBC Staff response: Process energy loads that exceed 25% of baseline
energy cost do not get reduced to 25%; project teams should use that energy
cost percentage for the model.

 

Thank you.

 

Thornton Energy Consulting

p. 503-231-6600 f. 503-231-3555

thorntonenergy at comcast.net

 



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