Does someone know how are we to design baseline when we have natural ventilation?  According to ASHRAE 90.1 - 2010 Table G3.1.1A, we have to use System 7 as baseline HVAC System Type, where we have to put in mechanical ventilation as way of conditioning the room. 

Reference Guide states:
"Natural ventilation: The ASHRAE User’s Manual indicates that an exceptional calculation method is not required for natural ventilation and gives some further examples. Perform sufficient analysis to document that loads can be met when credit is taken for passive cooling and natural ventilation using a simulation tool capable of ensuring thermal conditions are met with natural ventilation. A simple load calculation is not sufficient."

Is IDA-ICE simply not the right tool for this or are we missing something entirely?
Any other input or things to look out for?