Forum discussion

NC-v4 EAp2:Minimum energy performance

v4 DES baseline system modeling for multiple buildings under LEED campus

We are trying to submit to LEED v4 for a site with multiple buildings using LEED campus path. The whole campus is served by central chiller and boiler plant. And we are taking full DES performance accounting (option 1, path 2).

Our question is what is the right baseline system to use for buildings on site that are < 25,000sqft, which is system type 3 PSZ-AC per Table G3.1.1A in regular single building case. In our design case, the building is conditioned by a VAV system that receives chilled and hot water from the central plant on site. 

Do we still model the baseline system as PSZ-AC with DX coil or do we model it as single zone air handler with chilled and hot water coils that are served by a central boiler + chiller plant? (There is one large building on site which the baseline will be system type #7 with VAV reheat system + chiller + boiler, if that makes any difference.) Thanks.

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Fri, 07/13/2018 - 14:52

Under this path you model the baseline systems according to Table G3.1.1A, so DX coil and furnace for a System #3.

Tue, 08/14/2018 - 23:12

Hi Marcus - we were just trying to answer a similar question.  Note that in the DES guidance for v4, the language for Path 2 "Baseline Plant" says "Model the baseline case with an on-site plant that is compliant with ASHRAE 90.1–2010, Appendix G, baseline requirements for site-generated thermal energy."     Additionally, the Excel calculator [v4_Minimum Energy Performance Calculator] in the General HVAC tab has specific language in the Baseline Air-Side HVAC section that indicates that certain info (e.g. efficiency ratings for DX equipment) is "Not required if District Cooling has been selected", which seems to indicate that Path 2 wants you to modify the typical Baseline system to include a plant.   Are we to read the Reference Guide language to mean "IF your baseline has a plant per Table G3.1.1A, then follow the rules in this paragraph, but if your Baseline doesn't have a plant per Table G3.1.1A then ignore this paragraph"?   Any insight into the language in the excel file referencing "not required if District Cooling/Heating..."?   Thanks much.

Wed, 08/15/2018 - 14:22

We agree that the language is very confusing. In the previous version of the DES(v2) there was a table that showed you how to model the baseline systems which had you change everything associated with a DES to water based systems. This was very clear. Absent this table there is no guidance in Appendix G that tells you what you are supposed to do in the baseline. So our opinion is that you should use Table G3.1.1A. If GBCI wants us to use water-side systems instead of Table G3.1.1A then they should restore the missing table from the old DES guidance. Based on the MEPC it appears that they want a water system in the baseline. Given the obvious conflict and confusion I think you could make the case that you could do either option in the baseline and they should allow it.

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