We are working on a project with two buildings on one site, one commercial C&S, one Hotel. The two buildings are sharing some thermal plant, but it is only a condenser water loop – one central cooling tower set, one boiler plant to boost the loop. Both systems will be water source heat pumps, but separate submissions for LEED (and code).
I reviewed the "Treatment of District or Campus Thermal Energy in LEED" document to try to determine how I should submit my project, but it has made me more confused. The campus document talks about a DES as being a system that provides thermal energy “heating via hot water or steam, and/or cooling via chilled water”. Since this is neither, and following the Option 1 path will drive both baseline and proposed far from what is actually in the buildings, should we just ignore the central plant and treat them as separate water loops? There are theoretical energy savings from putting two buildings with different profiles on the one loop, and capacity reductions obviously, but using the guide doesn't seem any kind of logical.
I am leaning towards just giving each building a separate loop, but this won't match the drawings, I want to be sure that GBCI will actually accept the approach I take.
Thanks
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5906 thumbs up
May 24, 2016 - 11:33 am
No treating them as separate loops is not the best way to proceed.
You should apply DESv2 Option 2. You will need to model both buildings together to determine the plant efficiency and then produce separate modeling results that apply the efficiency of the plant. You can do this all within one model by creating separate meters and proportioning the loads on the plant to each building.
MKK LEED
MKK Consulting Engineers1 thumbs up
May 24, 2016 - 11:56 am
Hi, I can do the separate meters to achieve that, but in the DESv2 guide it says that for Opt2 my proposed district heating should be a virtual on site hot water or steam system, and my cooling should be a virtual on site chiller. I don't have a chiller on my site, and the boiler is only to top off the condenser loop, so what they want me to model will not represent my actual building.
I have now been pointed to a LEED interpretation (ID# 5234) that deals with a similar system, though they have geothermal in addition to the cooling tower and boiler. The interpretation states that "It appears, based on the description, that the building does not fall under the District Energy requirements, in that it is not provided with cooling or heating from a district source, but rather provided with condenser water which feeds heat pumps that produce the cooling and heating within the building." Based on this it is exempt from the DES guide, which would support just ignoring the shared plant. Unfortunately this referenced v1 of the DES guide so I'm unclear if it is still relevant, it does say it is also applicable to LEED2009.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5906 thumbs up
May 24, 2016 - 12:23 pm
I would suggest you apply the principles espoused by the DESv2 and not get hung up on the specific words. I agree it is not a perfect fit but if you apply the principle that you are proportioning the loads used from the shared loop it is basically the same as having a virtual on-site system.
You may be able to make the case that your system is not covered by the DES and not use it. This however will be considerably harder to do because you will then need to prepare a rather extensive justification for the modeling method you do apply if it is not in alignment with the DESv2. If you do choose this path it would be a good idea to submit a project specific CIR.
MKK LEED
MKK Consulting Engineers1 thumbs up
May 24, 2016 - 1:09 pm
So I can interpret the virtual onsite system that provides hot and chilled water as a virtual onsite system, but one that doesn't necessarily supply at boiler and chiller temperatures? I suppose it does say representing the upstream DH and DC systems, and since mine is condenser water that can be my represented plant. I have no problem with the combined model with meters in general. Thanks for the help
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5906 thumbs up
May 24, 2016 - 2:16 pm
Yes you can and the intention is clearly for you to represent your upstream plant.