Help determining Baseline System for Model

Marcus Thank you for getting back to me so quickly. Gas was added to the system by the owner to facilitate a morning warmup. Gas is not used at the terminal units, only on the RTUs. It's not clear to us how to get the model to be the same in terms of actual functionality unless System 6 is chosen and the morning warm up it not considered as part of the regular operation of the system. Again, any additional insight would be extremely helpful.

Marcus Allow me to throw one more interpretation at this. To clarify, we CAN model the rooftop unit gas fired morning warm-up functionality separately from the electric reheats. I mis-typed that comment above. There are a few issues we have discovered, most notably, under 90.1-2007 Table G3.1.1A, where the primary system type is determined ( i.e. - fossil/elec vs electric/other), there is a footnote: "Where attributes make a building eligible for more than one baseline system type, use the predominant condition to determine the system type for the entire building." It seems that this footnote is applicable to our building. We are eligible to choose either system type (fossil/elec hybrid OR elec/other), and because electricity is the the predominant fuel source for the entire building, the building should be modeled using System 6. In our building the morning warm up is only used for 1 hour. After that time, the system switches to all electric operation, which becomes the predominant fuel source 23 out of 24 hours of the day. Otherwise, if the owner had purchased his rooftop units without gas heat and relied on the electric heat at the FPT’s (a less efficient “proposed” system), Appendix G would allow the baseline to be System 6 without referencing the footnote. (( I should add: The footnote to Table G3.1.1A mentioned above allows Appendix G to be more in-line with Section 11, which also allows for selection of the predominant fuel use when determining the energy system for both the Baseline/Budget and Proposed cases. Without the footnote, Section 11 and Appendix G conflict one another. )) Do you read this the same way?

Marcus Do you mind providing a CIR # or reference for the CIR in question? I have combed the database and I don't see anything that addresses the issue to this level of granularity. Also, as mentioned above, the language in Table G3.1.1.A mentions the "Predominant Condition." We read that as being electric heat as the table directly addresses the fuel type selected for the baseline model. How do you interpret "predominant condition" in this case? Thanks again!!!

Thanks Marcus This is unfortunate. By this interpretation, the Owner would have been better off leaving out the gas for morning warm up and sticking with an electric warm up, which is far less efficient, for the sake of the LEED points. Seems the project gets penalized in this case for attempting to be more efficient. Being an existing system, the extent to which the Owner was able to replace or retrofit existing VAV boxes was substantially limited. The project scope was limited to only the packaged RTUs. I appreciate your feedback.