Building Envelope in Baseline for Major Renovation

In the Baseline model for a major renovation, for the envelope part: Do we use the “normal” Baseline elements as are in appendix G or do we model the envelope as it was before the major renovation (table G3.1, 5, f)? Just reading this sentence tells me that we should model it as it was before the renovation in Baseline. But when we read in UM that Existing buildings include when unconditioned space is converted into conditioned space or when an addition is made, then I’m wondering what the definition of Existing Building is in ASHRAE. If an old building with an old envelope is being used, new windows are put in, more insulation, new façade and a completely new interior is built, but it will remain as an office just like before. Which is it then?