Overall System Strategy and Implementation
I modeled the HVAC system for the entirety of both floors of the building. I have vertically packaged air handling units at the center of each floor, which would connect to air supply and return ducts to provide both heating and cooling to the building. Since the mechanical rooms are at the center of the building, theoretically there would be access to outside air through the roof (this is not modeled). Ideally the duct systems would be below the structural system, or somehow interwoven with the beam orientations with potential beam penetrations (for the structural engineer to analyze).
I began by allocating spaces and adjusting their use/occupancy. I also combined spaces into zones. I provided sufficient air terminals for the airflow demands using the approximate equation. Theoretically there would also be heating/cooling/airflow benefits coming from the shading, glazing, windows, etc.
The connection of the ducts to the AHU was not explicitly modeled, but the ducts are currently leading into the mechanical rooms. The auto-sizing feature was used to appropriately size all of the ducts, with height restrictions set in order to prevent the ducts from intruding too much on the ceiling height. Since I have structural walls in the middle of the building, I routed the ducts to avoid penetrating those walls. I also avoided routing any ducts through the atrium spaces, so the first floor atrium demands are supplied by the second floor.
HVAC Challenges
It was challenging to model the ducts and terminals to avoid clashes with each other and to allow the auto-sizing feature to work. Currently there are clashes between the return and supply ducts which would require careful adjustment of placement heights and restricted duct heights.
While I kept the structural system in mind, there is a lot of further coordination to avoid clashes between the HVAC and the structural system, which may involve re-orienting beams and adjusting heights/depths. On the 2nd level, there would be the added complication of trying to route the ducts around the trusses.