Which area type should be considered for simulation?

A question has been raised regarding which space area (GROSS or NET) should be considered into the simulation thermal blocks conception in order to result in the most accurate results. The project team came up with the following discussion: •There is a concerning that if GROSS area is considered, the thermal blocks will not represent the real designed space volume, and therefore, this will result in extra fan energy consumption; •On the other hand, if NET area is considered, the model will have a reduced gross external wall area if compared to the real designed building, and also effect on the energy consumption results accuracy. In relation to LEED and ASHRAE 90.1-2007 Appendix G, which option described above would be the most appropriate to consider?