Hi, I have modelled a project following Appendix G. I received review regarding HVAC system baseline type selection. The project is a mayor renovations + Additions (existing conditioned warehouse + New office building attached). First Question. The existing HVAC was modelled identical in Baseline and proposed since there were no changes. Is this right? The review says "Existing mechanical systems should not be model in the baseline". I'am a bit puzzled. Second. The new office building addition is heated fully with electric reheat coils. The existing warehouse is heated by gas boiler and hot water reheat coil. I modelled existing bit identical in proposed and baseline. For the baseline of the new addition I modelled system 6, since its all electrical heating. The review says the baseline is 5 because there is a boiler heating. Boiler is in the existing part. Again, I understand, not very sure I agree. Any thoughts? Thanks in advance. Santiago.

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Mon, 11/04/2013 - 15:19

There are some differing opinions on this subject. If the reviewer has not been clear about what you should do I would seek additional clarity. If you feel strongly that how you have modeled it is correct you could submit your approach to GBCI ahead of your final review response to see if it would be acceptable. First - In our opinion the existing mechanical equipment should be modeled identically. If GBCI is telling you that the warehouse should be modeled in the baseline and it is heated only consider a system 9. Second - It sounds like G3.1.1 exceptions (a) (b) or (c) might apply. I agree that since the gas heat serves the space that is not changing and the new space has electric heat it should be an electric system. This seems to allow the comparison of electric to electric and gas to gas which is clearly an intent within Appendix G. Again you might want to seek clarity before your final submission.

Zonda E. Team

Zonda Engineering

LEEDuser Basic Member

3 thumbs up

Mon, 11/04/2013 - 16:31

Marcus, thanks for the response. It is good to know this is an arguable interpretation and not just a big mistake. The reviewer has been very clear about what I'm expected to model though. So while I proceed to change my model's baseline, I will seek clarification since this will probably affect hugely in the energy savings (Client won't be very happy!). I will post back with a follow up since I believe this kind of discussion are very valuable for the modelling community. I have another question regarding modelling existing envelope, which I would appreciate your opinion, but I will start a new thread so that it is easy to find. Thanks.

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Mon, 11/04/2013 - 16:26

Modeling existing envelope is far more clear, see Table G3.1-5 Baseline (f). That is the problem with existing HVAC - Appendix G does not clearly state to model the existing conditions in the baseline. For me it makes far more sense to do what makes sense in alignment with the intent of 90.1 and Appendix G rather than to take such a literal approach. 90.1 in general does not apply to a project if you are not making modifications to that system (i.e. you do not have to bring the envelope, lighting or HVAC up to code unless you replace/retrofit it). Appendix G is for determining the savings of your project. Any issues that result in positive or negative savings not related to your project should be held neutral IMO.

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