residential or commercial

Jim, "residential" and "commercial" can mean different things depending on the context - whether you are trying to pick the appropriate LEED Rating system, say NC vs. Homes, figuring out the appropriate zoning code, or the appropriate energy code/ standard. Im not sure what you were referring to when you mentioned system 1 or 7, so if you need detailed help on EAc1 you may want to post on the forum for that credit. As a general answer, the commercial energy standard ASHRAE 90.1 also applies to residential buildings four stories and taller, so even an apartment building is sometimes defined as a commercial building for energy modeling.