Ventilation - Proposed and Baseline per ASHRAE 62.1-2007?

Hi! I am conducting a LEED v2009 EAp2/c1 energy model for a nonresidential building that is more than 5 floors. The proposed system is a water source heat pump system (WSHP) with natural gas boilers. Per Tables G3.1.1A&B of ASHRAE Standard 90.1-2007, the baseline system is a System 7 – VAV rooftop with Reheat. My question involves the ventilation rates for the proposed system vs. the baseline system. Per section G3.1.2.5 of ASHRAE 90.1-2007, minimum outdoor air ventilation shall be the same for the proposed and baseline building designs. Furthermore, per LEED v2009 IEQp1 Minimum Indoor Air Quality Performance for New Construction/Mechanically Ventilated Spaces, the proposed building’s mechanically ventilated systems must be designed using the ventilation rate procedure in ASHRAE Standard 62.1-2007. If the baseline VAV system is designed using the same ventilation rate procedure in ASHRAE Standard 62.1-2007, the baseline ventilation airflow rate is different (i.e. much greater) than the proposed ventilation airflow rate. The reason behind this is the larger sample size of system ventilation efficiencies for the VAV rooftop unit; this is because a VAV rooftop unit serves more spaces than a horizontal WSHP. The energy cost needed to condition the outdoor air is much less for the proposed WSHP design, which significantly improves (decreases) the proposed building’s annual operating cost over the baseline’s. Since I am choosing to use a WSHP system for my proposed design, shouldn’t I take the code-required ventilation advantages into account when conducting my model? Please let me know what you think. Thanks,