We have a project that is a major renovation of an existing building. We are planning on using the Existing envelope pathway - and thereby keeping the existing envelope in both the Proposed and Baseline building, which also allows us to take credit for improvements of the envelope in the Proposed building.

How is this handled for parts that are new construction? The building is expanded with 3 more floors on the existing top floor. Is it possible to comibine existing and new construction so that in the Baseline we use ASHRAE 90.1-values for the new construction and existing envelope for the lower floors? Also, since the baseline building shouldn´t be rotated for an existing building - is this ignored for the top floors as well (new construction)?

Thanks in advance,
Regards,