Parking Garage Demand Controlled Ventilation

Hi there, When a proposed building model includes parking garage DCV based on CO - How should the control of the baseline model garage fan volume be controlled?. Should the baseline model also control ventilation based on CO level or can it be at a fixed volume? ASHRAE 90.1 doesn't seem to describe control methodology or schedules for parking garages which is surprising given how significant the energy consumption can be. We have submitted preliminary design stage documentation and had provided an exceptional calculation with fixed flowrate control for the baseline model and the proposed based on CO. We received the following comment back from the assessor: "The Baseline case description should provide evidence that garage demand control ventilation is not standard practice for similar newly constructed facilities (three facilities built within the past five years of the project registration date) where the project is located" Where does this requirement come from? - it's certainly not in ASHRAE 90.1. Why is DCV for parking garage extract so special that it needs to be demonstrated it's not common practice at the site location - we don't need to do this for any other energy conservation measures? The prerequisite criteria is based on demonstrating a percentage improvement compared to ASHRAE 90.1-2007 - not compared to what is typical practice at the site location... I would have thought LEED would be promoting DCV rather than making it more difficult to achieve credit for doing the right thing. Cheers