I have a project that is classified as a high rise residential building. In the proposed design, the living units are conditioned by water source heat pumps and ventilated via natural ventilation (operable windows). Four 100% -outside air units (each about 10,000 cfm) supply outside air directly into the corridors.
Since we don’t plan to claim any energy savings from natural ventilation, I intend to model zero ventilation air in the living units both in the baseline and proposed case and the same amount of outside air (a sum of minimum exhaust rates for residential kitchens, bathrooms and dryers) introduced into corridors in both the baseline and proposed case.
Question 1: What would be the appropriate baseline system for dedicated outdoor air units? Since our main baseline system is PTAC, I would use a constant volume system with DX cooling/air cooled condenser and hot water fossil fuel boiler as a heating source. Our design selection is a 100% outdoor air unit with DX cooling /evaporative-cooled condenser and natural gas heating. Are we allowed to take credit for evaporative-cooled condenser, or we are required to model the same condenser cooling source in the baseline and proposed case? For example, if we switch to 100% outside air water cooled heat pumps, should our baseline dedicated outdoor air system remain DX cooling/ air cooled condenser and hot water coil?
Question 2: Can we use min exhaust rate per ASHRAE Table 6-4 and equation per Table G3.1.2.9 to size exhaust fans for unconditioned parking garage and take credit by comparing it against the proposed design BHP.

I would greatly appreciate your opinion.