Dear Sirs, I just noted the following paragraph in the "Treatment of District or Campus Thermal Energy in LEED V2 and LEED 2009" document: "LEED v2009 projects are not formally required to use this guidance at this time, but using it is highly recommended to help ensure a smooth LEED certification review. USGBC is working to incorporate this guidance into LEED v2009 more formally, but that process is not yet complete." 1) Is this true? I also noted in the latest Excel Table 1.4 (used to demonstrate compliance with this prerequisite), one has an option to select how the DES has been modeled (in the "General HVAC" tab). One can select ASHRAE 90.1-2007 Appendix G, or DESv2 Option 1, or DESv2 Option 2. 2) By selecting ASHRAE 90.1-2007, does this mean that my proposed scenario will also be based on ASHRAE 90.1 (same as the baseline scenario)? If this is the case, then a project will not be able to obtain savings in HVAC items, right? Thanks!

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Thu, 01/30/2014 - 14:49

1) yes the DES is optional. 2) Not that simple. In lieu of following DESv2, you can follow ASHRAE 90.1 2007 Appendix G modeling protocols, with or without ASHRAE 90.1 2007 addendums, e.g., addendum ai. If following ASHRAE 90.1 2007 district energy modeling protocols, without addenda, the heating source must be included in the energy models as purchased heat using identical energy rates in the baseline and proposed case energy models as indicated in ASHRAE 90.1 2007 Section G3.1.1.1, and the cooling energy must be modeled using purchased energy rates in the proposed case and the appropriate Appendix G baseline cooling system in the baseline case. If applying ASHRAE 90.1 2007 addendum ai, refer to ASHRAE 90.1 2007 addendum ai, Sections G3.1.1.1.1 through G3.1.3.10, for heating and cooling energy requirements. Note that any ASHRAE 90.1 2007 addenda implemented must be applied in whole and consistently across all LEED credits and prerequisites, and the submittal documentation must clearly indicate any addenda that have been applied to the project documentation. Also make sure to fully explain the modeling approach taken and do not assume that the reviewer can figure it out based on your input summary alone. Depending on the approach there may be certain elements of the HVAC systems for which you would not be able to claim any savings.

Maya Karkour

EcoConsulting

LEEDuser Basic Member

549 thumbs up

Thu, 01/30/2014 - 17:23

Thanks Marcus, this whole District Energy thing is getting annoying; I never anticipated it would be that complex. I have a few more questions running through my head: 1) I’m looking at ASHRAE 90.1-2007 App G and the addendum ‘ai’. It appears to be similar to the DES guide, Option 1 (Streamlined, the building stand-alone scenario), in the sense of modelling purchased energy, probably with a couple of minor differences. Do you have a preference as to which one is simpler? 2) I was wondering what really happens when I model “purchased heat” by modelling a hot water meter. Will the software calculate the heating demand from my building at each hour, and “purchase” or “withdraw” the exact amount of required hot water from the hot water meter? 3) In this case, this “hot water meter” is acting as a boiler. Will the software assume that the building can use as much water as required (so the heating source is always available to provide whatever amount of energy required by the building at all times)? 4) The hot water meter has a parameter called “source-to-site efficiency”. Do I need to enter the efficiencies from Tables 6.4 (Mandatory Provisions) of ASHRAE 90.1 for the baseline scenario, and whatever the heating efficiency is for the proposed district heating? 5) In my proposed scenario, the hot water pumps are located in the campus plant (outside the building perimeter). Do I need to add these pumps to my hot water loops, or do I need to add them as direct loads on the electricity utility meter (& assume a logical operation schedule)? 6) I'm assuming the same answers apply to Purchased Chilled Water when following ASHRAE 90.1-2007 Addendum 'ai'. You input is much appreciated – the thing is that there is no 100% complete & clear guide / manual to help people proceed step-by-step, so we have to resort to LEED forums, modelling software forums, “dissect” through ASHRAE standards / LEED publications, etc. Thanks again, Omar

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Thu, 01/30/2014 - 17:56

1) they are basically identical 2) sounds right 3) The hot water is simply treated as an energy source. For the Baseline it would be auto-calculated. For the Proposed it is based on the design. 4) If you model purchased energy you do not enter an efficiency or conversion factor. 5) The central plant pumps are not taken into account if modeling purchased energy. 6) yes The forums are nothing more than free consultants. You could hire one who could help you get up the learning curve easier. In this case you only need ASHRAE 90.1-2007 plus addenda and the DES v2. Learning curve for anything new and somewhat complex is always steep, especially by yourself.

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