Definition for Ds (%)

D is the same as Ds. The s is a subscript to represent diversity at the system level. D is described in Chapter 6 of ASHRAE 62.1.

Nena/Roger, I think there is some confusion here. D is not the same as Ds. D=Diversity. Either in regards to the population served by the system vs FTE or the sum of all your zone maximum supply quantities vs your system capacity. Example: Your office spaces has a ventilation design capacity of 50 people and your conference rooms have a design capacity of 50 people. But your FTE is only 50 people. Your population D=50%. This reduces your outdoor air intake requirements. Ds=Percentage of total design airflow rate at conditioned analyzed. Example. You have a VAV system with a 50% turn down for heating mode. Ds = 50%. Ds is typically the turn down at the terminal (for the design condition). For a VAV system, it is typically between 30-50%. For a constant volume system, Ds=100%. A lower Ds will give you a lower Ev coefficient, resulting in higher OA intake requirements. On LEEDOnline, go to the main page for IEQp1. Then on the right, under quick links is a link to "Credit Resources." Download the "62MZCalc" excel file. Although it may confuse you more, at least there are some directions and definitions in that file.