Bldg-sim Digest, Vol 73, Issue 7

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I would like to add to this discussion, a couple of months ago we had an interesting review comment from LEED on this issue and it has rattled us a little. There is a definition of whether a building is one or two. Off the top of my head I can't remember where it is (sorry for that not terribly useful) but we had a two buildings connected by a corridor all fed with the same boiler and chiller. LEED specifically told us that because it was only connected by a corridor it had to be regarded as two separate buildings. We had to change LEED certifications and redo a huge amount of the energy model in order to split the energy usage in two. I would suggest that you contact LEED to check you are doing the right thing, it will save you hours of pain and money. This is all assuming you are doing LEED, I know that this definition was not in 90.1 it was somewhere else in LEED documentation.

Annie Marston, Ph.D. LEED AP, BEMP

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Hi Annie,

This issue you are facing is a LEED issue and it is defined by the
LEED Minimum Program Requirements (Jan 2011), Suplemental Guidance to
the Minimum Program Requirements Rev 2 (Sep 2011), and LEED Aplication
Guide for Multiple Buildings and On-Campus Building Projects (Oct

The LEED MPR defines a super structure (single buildings) when two
structures are linked by a space other than a corridor or park garage
(maybe regularly occupied space). Therefore you would have to use the
Multiple Buildings and On-Campus rulings and for energy modelling. The
multiple building works as a single LEED certification for a group or
buildings where each building or both buildings combined must comply
with the requirements. On-campus project works in two stages, you get
the site related credits on a first stage and then you may proceed
with the certification of buildings inside the campus.

Dionisio Franca

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The original poster said he didn't have a LEED project, but you are correct that LEED has their own guidance on how to treat buildings and campuses while using 90.1 mostly as-is. Your project may have had unfortunate timing. I don't know if separating the buildings has been strictly enforced before now. Or if some may still pass through in some cases? This is one of the first times that I've heard of it coming up mid-stream as opposed to allowing the project team to help define which case it should use.

Although it seems like a lot of extra work to separate these two buildings for an NC certification, it would be consistent with eventual EB: O&M certification which would be based on separate ENERGY STAR accounts for the two buildings, so I can see the argument in favor.

I would hope that USGBC would allow you to have both buildings in a combined model as long as each had its own heating and cooling loops and electricity meters -- all pertinent energy usage, demand, and cost could be provided to the reviewer even if the model was combined. I think it's a step too far by the reviewers if they forced you to have two separate models.

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP

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Thanks, I wasn't sure if it was a LEED question or not, luckily a very different answer as it wasn't.

Annie Marston, Ph.D. LEED AP, BEMP

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Joined: 2011-10-02
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You can always certify these buildings together as LEED for Multiple Buildings:

If they share mechanical plant/equipment, you can put them together in one energy model. I'm in the comment review phase on a 6 building certification healthcare project. Two of the hospitals are served by the central plant building (with no other buildings served). The energy model was performed with both hospital buildings and the central plant building in one model. The other three buildings are multi-family apartment buildings with stand-alone mechanical equipment. Those have been modeled individually in separate models. The Baseline and Proposed energy costs are then all added up for all 4 models to calculate energy cost savings. This aggregation is performed in a spreadsheet. This methodology was confirmed with a GBCI CIR beforehand.

If you're certifying multiple buildings together, which it sounds like you are trying to, I've never had problems in the past putting independent buildings in one model (even if they don't share mechanical plant). Hopefully this doesn't mark an about-face from GBCI on this topic. The LEED reviewers have gotten better recently about direct communication with the design team. I recommend you seek clarification from them before proceeding and using lots of hours.

Best of luck,

Scott P. West, P.E., LEED AP BD+C, BEAP, BEMP

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