Hi
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