[Equest-users] Another DCV question - when to claim credit per G3.1.2.5?

[Bishop, Bill]

The proposed design has DCV. I would like to use the G3.1.2.5 exception to take credit for it. Maria, you seem to be saying that I should model DCV in both the proposed and baseline, unless I didn't have DCV in the proposed, in which case I should model it in neither. Do I understand you correctly?

Thanks,
Bill

From: Maria Karpman [mailto:maria.karpman at karpmanconsulting.net]
Sent: Tuesday, May 21, 2013 10:10 AM
To: Bishop, Bill; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Another DCV question - when to claim credit per G3.1.2.5?

Bill,

I interpret this exception as "G3.1.2.5....Exception: When modeling demand-control ventilation in the proposed design when its use is not required by Section 6.4.3.8" for the baseline design  (section G3.1.2 is titled General Baseline HVAC System Requirements")

If I understand your situation correctly, the baseline systems in your project are not subject to G3.1.2.10, and do not meet any of the exceptions to 6.4.3.9. If this is the case, then I believe you have to model DCV for these systems in the baseline. Proposed systems do have energy recovery, and thus do not require DCV due to exception to 6.4.3.9, so DCV does not have to be added in order for the project to meet G1.2 prerequisite.

To summarize, you have DCV in the baseline and no DCV in the proposed design, which is reverse condition compared to that described in Exception to G3.1.2.5. This means that the exception does not apply to your project and you should model the same ventilation rates in the baseline and proposed designs. Following this logic, if you add DCV to the proposed design, you'd just break even with the baseline which also has DCV. The proposed design might have an edge because it also has energy recovery, as long as the associated fan power penalty is not too punishing.

Thanks,

Maria


From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
Sent: Monday, May 20, 2013 7:03 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] Another DCV question - when to claim credit per G3.1.2.5?

[This is a LEED/Appendix G question - not an eQUEST-specific issue. My apologies if this has been answered before. I didn't see it in the archives.]

Can a proposed design claim credit for DCV if DCV is not required for the proposed design per 6.4.3.9, even though DCV would be required for the baseline under the same criteria?

Proposed designs modeled for LEED and/or Appendix G can claim credit for reduced ventilation rates per the exception to ASHRAE Standard 90.1, G3.1.2.5.
The exception is "When modeling demand-control ventilation in the proposed design when its use is not required by Section 6.4.3.8." [The typo appears in App. G. 2007 - should be "6.4.3.9".]

My proposed design does not require DCV per 6.4.3.9, because all of the systems that serve spaces meeting the DCV requirement also have energy recovery, which is exception (a.) for 6.4.3.9.
Therefore, I would argue that the proposed design can claim credit for DCV.
However, none of the baseline systems that serve the same spaces meet the G3.1.2.10 requirement for energy recovery. The baseline systems do not meet any of the exceptions to 6.4.3.9.

Does the exception to G3.1.2.5 imply "...when its use is not required in either the proposed or baseline design"?
I'm hoping not, otherwise this is a blue Monday<http://www.youtube.com/watch?v=FYH8DsU2WCk>. Tell me how you feel.

Thanks,
Bill

William Bishop, PE, BEMP, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

134 South Fitzhugh Street                 Rochester, NY 14608
T: (585) 325-6004 Ext. 114            F: (585) 325-6005
bbishop at pathfinder-ea.com<mailto:wbishop at pathfinder-ea.com>           www.pathfinder-ea.com<http://www.pathfinder-ea.com/>
P   Sustainability - the forest AND the trees. P

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