[Equest-users] Requirements for Same OA in baseline and proposed?

[Karen Walkerman]

I see your point, although I usually just toe the line and force the OA
percent to be different in each zone. If you want to pursue your approach,
calculate the outdoor airflow for your baseline system using the ASHRAE
62.1 spreadsheet provided for the IAQ credits. Use the minimum amount of
system ventilation air required. You'll find that for a multi-zone system,
the outdoor air is shared between zones, with some penalty, but it's not as
bad as forcing the whole system to be 50% outdoor air simply because one
zone requires it. I won't gaurantee that the reviewer accepts this, but you
need to calculate ventilation this way in order for your argument to be
consistent.

Karen

On Saturday, August 18, 2012, Chris Mullinax <chris at mullinaxsolutions.com>
wrote:
> I’m working on a LEED project with the following conditions:
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> 1)      The proposed system is a 4 pipe Fan Coil system. Outside air is
brought into the space through an central ERV and independently ducted to
each Zone.
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> 2)      Appendix G requires the Baseline case to be Packaged VAV for each
floor, with terminal re-heat for each zone
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> In my simulation, I have the outside air being calculated based on the
“critical” zone for the baseline case. In order to meet the needs of the
critical zone, outside air for each floor is increased to meet the critical
zone needs.  Outside air for the proposed system is simply the sum of all
the zones, because each zone is supplied individually.
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> The net result is that the OA in the baseline and proposed simulation are
different, because the PVAV system has to adjust the OA upward for the
critical zone.
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> The reviewer has commented that the outside air must be the same for both
simulations.
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> This seems like a paradox to me.   It is physically impossible to make
15% OA go to one zone and 20% OA go to another zone in a PVAV system, where
the OA is mixed in the AHU prior to distribution through a common duct.
 Forcing my simulation to do this in order to meet the reviewers comments
seems to violate the spirit of LEED. Why would we purposefully compare a
proposed system to baseline which cannot be built?
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> Likewise, artificially raising the OA used in the proposed system
simulation, to match that of the baseline system makes no since.
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> Has anyone else run into this before? Do you have suggestions?
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> All help greatly appreciated!
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> Regards,
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> Chris D. Mullinax, P.E., LEED AP, CEM
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> Mullinax Solutions, Inc.
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> pn: 770-387-1334
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> fx: 770-387-1383
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> www.mullinaxsolutions.com
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> P Please consider the environment before printing this e-mail
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