LEED Boundary

I had a similar question on a recent project. The guidance that I received from my LEED Coach stated that although the parking garage would not be included within the gross square footage of the project, the LEED Project boundary should be drawn to include the parking structure, given that it is being built within the same scope to support the project, as outlined in the Minimum Program Requirement - Must use reasonable LEED boundaries (https://www.usgbc.org/node/2742911?return=/credits/new-construction/v4/minimum-program-requirements). However, you might want to check with your LEED Coach given your statement that the garage will be constructed in a different phase.

Good advice, Summer, to check about the phasing - the garage would need to be complete by the time of the construction phase submittal if it's contributing to credits like heat island reduction, light pollution, etc.  

Miguel - also check the credit language and MPR Summer referenced if the garage will serve other buildings. You'll need to allocate a percentage of the parking spaces, LEV/ priority spaces, any bike racks, to other buildings if the garage will be shared. It might be hard to estimate the square footage and FTE numbers for unbuilt projects outside of your control, but you could use the zoning code's allowable floor area ratio (FAR) or maximum density for guidance.

Once you have an estimated building area for any building(s) that share the garage, the Appendix 1 default occupant density can help you calculate the occupancy, and then parking spaces, green vehicle spaces, bike racks needed for the other building(s).  But if the garage is intended only for your building, that makes it much simpler.