62MZ Calculation for IEQ2 - For VAV Systems

Laura, I've asked around and haven't been able to gather any thoughts on your questions here. Have you learned anything more since posting this?

Hi, Laura- I am having the same issue right now on a CI 2009 project, Increased Ventilation Credit submission. Mathematically, within the 62MZ spreadsheet, what you are saying makes sense. However, I get the impression that it is not the Intent of LEED for us to have to increase the outdoor air "requirement" in each zone by multiplying the people and areas. Rather, to me, their intent seems to be that we calculate the requirement, then increase the required amount of outdoor air by at least 30% and distribute it so that each zone gets at least 30% more "unused outdoor air" than it would have at the minimum outdoor air intake volume. Some of the math seems to me to hinge on whether the extra 30% going to the breathing zone is now determined to be "used" and therefore is of no use to the other zones when it is recirculated. If you multiply the people and area by 1.3, then the extra air is considered used when it gets to the breathing zone of the space, and cannot be considered unvitiated when recirculated back as return air. But it doesn't seem like that is the LEED intent. For one thing, notice that the templates ask for the actual 62.1 breathing zone rates required; they don't check for the 30% factor until AFTER outdoor intake volume is calculated. Nonetheless, I am still not sure how to calculate the outdoor intake volume provided for a specific zone, especially a non-critical zone. I haven't submitted this yet, so I don't know what the response will be. Just letting you know my thoughts after hours of staring at spreadsheets Voz, Vot, etc.....

Laura and Tristan- While I'm still inclined to argue as in my March 18th reply above, I did receive comments from my LEED reviewer indicating that your approach was what he/she wants to see, Laura. Here is the reviewer's comment on my submission: "The LEED Credit Form has been provided stating that the project has increased breathing zone outdoor air ventilation rates to all occupied spaces by at least 30% above the minimum rates required by ASHRAE Standard 62.1-2007. However, the calculation has applied the 30% increase at the system level, and not at the zone level. To correctly determine the required outdoor airflow rate (Vot), the system ventilation efficiency (Ev) must be adjusted to reflect the 30% increase in the required breathing zone outdoor airflow rate (Vbz). TECHNICAL ADVICE: Please revise the calculation to determine the value of Vot as a result of the increased Vbz. This can be determined by any of the following: a. Increasing the people and area outdoor airflow rate values (Rp and Ra) by 30% in the calculation. b. Increasing the Vbz at the system level by 30% in the calculation. c. Increasing the uncorrected outdoor airflow rate (Vou) at the system level, and Vbz at the critical zone by 30% in the calculation." It's not worth it to try arguing to the contrary on this project. Maybe I will try it sometime in the future. To me, one key is whether the outdoor air "requirement" actually increases 30% as opposed to the "requirement" staying the same, but just providing 30% more to each zone than it requires.