Regularly Occupied

Chris, In general, if your vacant space is less than 10% of the floor area, you can choose to include or exclude it from any given credit at your whimsy. If vacant areas are greater than 10% up to 50% of the floor area, you need to follow the guidelines for accounting for those spaces in the technical guidance document issued by USGBC - info about the maximum allowable vacancy and a link to the guidance document can be found here: http://www.usgbc.org/News/USGBCInTheNewsDetails.aspx?ID=4190 Looks like for this credit, vacant spaces "may be excluded." This hints that you can include them if you'd like, but doesn't explicitly seem to offer that. Assuming you can include them, I'd think you'd definitely need to wholly do one or the other, and not selectively pick the vacant perimeter offices to include and leave out other vacant spaces in the interior that would be regularly occupied if the building were full.