Heating and Cooling Ez, and Occupant Diversity

It seems that the certification reviewers do not know when heating and cooling occur in a space. The cheat sheet the reviewer use tell them to challenge any calculations that do not show heating as the worst case compliance mode. Cooling is really the worst case, except maybe in an extreme situation. At 100% Diversity cooling should be the ventilation mode. The Ez is 1.0 for overhead supply. When heating occurs the occupancy should be lower. The Ez would be 0.8 for overhead supply. The diversity will be much less than 100% when heating occurs. The 20% difference in Ez does not for the above case never, as far as I can tell, results in a 20% increase in additional OA, if you assume maximum occupancy occurs whether heating or cooling is provided. For example, a single zone meeting space using default occupancies the change is 6% more OA in heating mode than in cooling mode, assuming that the occupancy is 100%. Not as much as you might think for a change in Ez from 1.0 to 0.8. If you were to assume occupancy is 88% (Diversity), again using a meeting space, then the required OA will calculate to be about the same as required for cooling mode. So, if you assume that heating only occurs when occupancy is less than 88% of the maximum, then cooling will always be the driver for the calculations. I am not a mechanical system designer, but what I see the actual designers doing when the LEED reviewers challenge them is using 100% occupancy, the Ez corresponding to heating mode. In other words, they respond by over-ventilating their buildings. The original intent of the ASHRAE calculation tool was use as a design tool. This I learned first hand from the primary developer of the tool when I was the vice-chair of the LEED IEQ Technical Advisory Committee. LEED has turned this into a bizarre compliance tool where opposing minimum requirements are incorrectly multiplied together. Buildings that are becoming more and more over-ventilated as a result. This is highly unfortunate and contrary to the objective of certifying energy-efficient LEED buildings.