I appreciate the answer to the following question:

With respect to LEED v3 commercial interior EA credit 3.1, how do we
approach the existing building HVAC system serving the entire building
including the tenant area seeking LEED certification. Shall we include
only new HVAC equipment serving the tenant area and consider the main
system as "EXISTING" in the energy modeling or we need to include the
building main system (e.g. chillers, pumps, air handling units). In
latter case, the entire building needs to be considered in the energy
modeling. Since the building main system may be somewhat old and not
very energy efficient, it may adversely affect the proposed energy
usage. In addition, in case the tenant improvement does not utilize any
new AC equipment (for instance only VAV boxes), what needs to be
included in the energy modeling to prove the compliance with 2007 ASHRAE
90.1 or 2008 Title-24.

Thanks,

Bruce Rohani, P.E., LEED AP, CPMP