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CI-2009 EAc1.3:Optimize Energy Performance—HVAC

Option 2 for LEED CI EAc1.3

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Alan Li
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I'm working on a project that pursues the CI EAc1.3 credit by following Option 2 using ASHRAE 90.1-2007 Section 11. If I understand it correctly, the baseline model not only needs to meet all the requirements in Section 11, but also all the mandatory and prescriptive requirements in each Section of ASHRAE 90.1, such as 6.4 and 6.5 for HVAC. Am I understanding it correctly? If that's the case, do I have to model both air economizer and water economizer for chilled water VAV systems for projects located in climate 4a, per ASHRAE 90.1-2007 Section 6.5.1? I'm not sure if Exception a in Section 6.5.1 can be applied to the VAV systems.

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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
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Mon, 03/21/2016 - 22:08

You need to meet the mandatory requirements. You can then do either a Section 11 model or an Appendix G model.You do not have to meet the prescriptive requirements when using a performance method. The specific modeling methodology is spelled out in the Reference Guide. Both Section 11 and Appendix g tell you how to model the baseline. You almost always model the proposed case as designed.
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Alan Li
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Wed, 03/23/2016 - 16:21

Thank you very much for your reply, Marcus! Yes, I would think that we don't need to meet prescriptive requirements when we use a performance method, i.e. Appendix G or Section 11 energy model. However, in Reference Guide for LEED CI EAc 1.3 HVAC, it states in Step 6 (pg171) that "For the baseline HVAC model (no modifications to the central plant), change only those items within the project area to the mandatory and prescriptive requirements of the standard". It does look like that we have to meet the prescriptive requirement too? If that's the case, it comes back to the question that I ask previously about the economizers. Do I have to model air or water-side economizers for VAV systems for projects located in Climate 4a, per prescriptive requirements 6.5.1?
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
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Wed, 03/23/2016 - 16:33

That sentence says that the baseline must meet the mandatory and prescriptive requirements. The proposed only needs to meet the mandatory so you do not have to meet the prescriptive requirements. If they are better than your design you pay a penalty, if worse you get savings. that is the nature of a performance based methodology. Refer to Section 11 or Appendix G for the requirements in the baseline related to economizer. For the proposed you are not required to implement all the prescriptive requirements.

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