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

[Maria Karpman]

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] On Behalf Of Bishop,
Bill
Sent: Monday, May 20, 2013 7:03 PM
To: 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

 <mailto:wbishop at pathfinder-ea.com> bbishop at pathfinder-ea.com
<http://www.pathfinder-ea.com/> www.pathfinder-ea.com

P   Sustainability - the forest AND the trees. P   

 

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