[Bldg-rate] LEED+90.1 Process/Plug LoadsConundrum

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Let me see if I can add some clarity to the reasoning behind the 25% process

First of all and most important ? every project should model what has been
designed/built and nothing more.

The 25% value was selected since that is a pretty typical plug load
percentage for an office building (LEED was originally created for an office
building and there are still vestiges of this lineage). This value was
never intended as a hard and fast minimum for all projects. The intention
was to make sure that all energy uses in any building were accounted for in
the model, unfortunately it has been widely misunderstood. This is an
indication that we have a problem in the LEED credit language. LEED 2012 is
likely to drop this ?requirement?.

The 25% had nothing to do with raising the level of difficulty. We clearly
understand that facilities with high process energy loads have a harder time
earning points in LEED than those with low loads. This is a problem for
many LEED projects and USGBC is slowly adding baselines for process loads so
energy savings can be claimed against them.

One should NEVER add non-existing loads to get up to 25%. This is
completely counter to the intention of this rule.

If you are under 25% James has it correct, simply document what you have.
Most typically this would include a spreadsheet and perhaps a narrative if
anything would need to be explained so the reviewer can understand the
situation. In the vast majority of cases this information should exist as
it is often needed in order to perform the HVAC load calculations correctly.
So I don?t really understand the perceived difficulty. For many building
types with only plug loads as process one can also use the W/sf values in
the 90.1 Unser?s Manual.

It is the intention of USGBC to make sure that the energy model addresses
all of the energy in and associated with the project. This was the intent
of the 25% rule. This language is in the credit requirement but its
connection to process energy is certainly not clear.

As a company that was one of the original 5 review firms, our reviewers will
question a project whose process energy is exactly 25%. This gives the
appearance that either non-existing loads have been added or even worse that
process loads have not even been included in the models and a value equating
to 25% was added to the modeling results. Again model what you have. If
over 25% do nothing. If under 25% document why.

Always keep in mind that the purpose behind modeling is to guide
design-decisions and to the greatest extent possible accurately project the
actual energy consumption of the facility. Under the USGBC?s Building
Performance Initiative and MPR #6 in LEED 2009, your modeling results will
be compared to the actual building?s energy use (although this comparison
will not be made public on an individual project basis) so every effort to
improve quality and accuracy should be taken.

Marcus Sheffer

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