Kelly: That's a good question. This is a sticky subject - we don't have specific guidance on this type of situation yet, but it should be included in the next version of the MPR Supplemental Guidance. I would recommend that you definitely exclude the footprint of the separate building. Something like a couple of feet ring around the perimeter of the separate building is probably fine too. But you'll need a good reason for additional excluded land that contributes to a donut hole in the middle of the LEED project site area. If an area is truly only supports the separate building's operations, as opposed to the LEED project building's operations, than excluding that area would be acceptable. In general, the rule of thumb is the (unfortunately) vague term ‘reasonable’ – if it looks like you drew a project boundary that makes sense and doesn’t leave specifically leave out land that would detract from compliance with a prereq or credit, it’s likely to get approved. If you’re really worried about something and want to get approval before your prelim review, send the question with a clearly labeled site plan to leedinfo@usgbc.org.
I wish I had firmer guidance for you, but it’s just not realistic for us to write policy for all eventualities – and we want to allow for some flexibility for project teams. I hope this at least points you in the right direction :).