Based on the fresh air volume in your example (108 l/s), the design air flow would have to be at least equal to that amount and probably higher unless the primary air handler is 100% fresh air. The design air flow based on 20F delta T should always be trumped by the ventilation requirement, if ventilation requirement is larger than it.

In any case, I would maintain a minimum of 0.4 cfm/sf as a minimum level of ventilation simply as "good practice" to avoid stagnation. This may mean using additional reheat energy or utilizing a fan-powered terminal unit to provide additional recirculation air.

However, if air stagnation is not a concern, and design air flow is less than 0.4cfm/sf then I would say that the minimum setpoint is at the discretion of the designer and any value less than or equal to 0.4 cfm/sf would not violate the intent of the requirement. In the same way, if the cooling design load required 1.0 cfm/sf but the heating load for the space could be handled with less than 0.25 cfm/sf then I don't believe App G would require you to increase your minimum VAV setpoint to 0.4 since that would be a silly waste of energy. The most extreme example of this logic is an interior zone, which has zero heating load and zero fresh air load...Since there is no reheat required, the 0.4 cfm/sf requirement does not apply and therefore the VAV damper could be allowed to fully close when the space is satisfied. Due to Standard 62 this occurrence is highly improbable, but it helps to illustrate the point.

That's my two cents.

Thanks,

Dan Russell, EIT