Existing building with extension

Our project is an extension building that undergoes a major renovation on the HVAC-system and interior, but not exterior envelope, and even gets a new extension. In total, the existing gross area accounts for almost 80% of the total gross area after renovation and extension and it is almost the same amount for the existing envelope in comparison to the exterior envelope after renovation and extension. How should the Baseline building be modeled? According to FAQs in the section, the existing buildings do not need to be rotated and the existing exterior envelope can be used for the Baseline modeling as well. However, in this building it is not possible separate the new part from the existing part in order to account the rotation only in the new construction part. Can I still rotate the whole building? Moreover, the existing exterior envelope has better U-values than the Baseline U-values in Tables 5.5-8. Can I model the Baseline building with an exterior envelope exact the same as in the Proposed building, that makes the modelling easier, and in that case not taking credit for a better exterior envelope of the new part of the Proposed building against the new part of the Baseline building with U-values from Tables 5.5-8? One last though, how shall I count the points in regard to the savings in the table under Option 1 for EAcr1 when considering the type of my building, new vs. existing building?