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

[Bishop, Bill]

Just change the system OA-SIZING-METHOD in the baseline to SUM-OF-ZONE-OA, like it is in the proposed system. I would argue that the G3.1.2.5 requirement that ventilation rates be the same applies first and foremost to the building as a whole, then to the systems, and then to the zones if possible. The intent is to make the ventilation load neutral between the baseline and proposed designs, not to simulate effective ventilation distribution in the baseline.

Regards,
Bill

[Senior Energy Engineer 28Jun2012]<mailto:wbishop at pathfinder-ea.com>

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Karen Walkerman
Sent: Saturday, August 18, 2012 6:53 PM
To: Chris Mullinax
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Requirements for Same OA in baseline and proposed?

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<mailto: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<http://www.mullinaxsolutions.com>
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> P Please consider the environment before printing this e-mail
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