Appendix 1 of the BD+C Reference guide states that "if the buildings and circumstances are not covered in this appendix, provide documentation for comparable buildings demonstrating average gross square foot per occupant..."

Something similar appears on the PI Form 3: "Actual Building occupancy is unknown and the defaultoccupancy counts do not adress the LEED building type. The project team will base occupancy on an alternative methodology"

For a building in Mexico city, 250 gross sf per occupant seems to be a very low occupant density. Of course, this depends on (and here is my first question) what is the definition of gross area? Does it includes below grade parking and all other enclosed spaces? and, what alternative methodologies are acceptable for using a different occupant density?