I am working on a residential building, with more than 20,000 SF of conditioned non residential spaces, so I am using System #7 for non residential spaces. I also have spaces with no HVAC system designed yet (spaces that shall be rented/leased). 90.1-2007 calls for each floor to be modeled with separate HVAC system for systems 5,6,7,8. Do I include my rented/leased spaces under the same VAV system that serves the rest of the floor, or should I create separate HVAC systems for these spaces? Also, does the one-system-per-floor rule apply if I have some single height spaces and some double height spaces on the same floor?