Natural and mechanically ventilated space: hybrid LEED model

> I am trying to model a hybrid system in Carrier HAP. We have a VRF system that utilizes dedicated outdoor air at a constant supply CFM as well as standard indoor recirculation units. We also have demand control ventillation modeled for the Proposed system in HAP to accomodate the natural ventillation as the "make-up" ventillation air required. The VRF system's outdoor air units do not meet the entire ventillation system requirements, as natural ventilation is used in the same spaces. The project is located near San Diego, so natural ventillation appeared to be a viable option. We needed the mechanical outdoor air ventillation to serve the additional space that is not within the 25' radius from operable windows and doors. > What is the best way to represent the hybrid model, since LEED certification will be required? Would an exceptional calculation be required, and if so, what is the "best" way to address it from a LEED reviewer's point of view? > We have a baseline system type 4. > > Thank you for your assistnce.