We have old existing office building where ducted FCU is serving all the spaces. Fresh air is dumped to the plenum (no ducts), likewise for return air, so mixing happen randomly within the ceiling plenum.

We have measured the fresh air at each level before it is discharged to the plenum, we have also measured the discharge at each zone terminal unit.

Our total fresh air is more than enough on floor level, however, for the ASHRAE 62.1 calculator we still need to input the primary air for each zone, so my question is: what is the reasonable / conservative ratio (zone primary air / zone discharge air) that LEED would accept? knowing that this is our second submission so no room for errors :D

Much appreciated

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Gustavo De las Heras Izquierdo

LEED Expert

LEEDuser Basic Member

169 thumbs up

Mon, 10/14/2024 - 15:07

Hi Omar, My advice is that you follow the simplified calculations method, so that you can disregard the zone primary air / zone discharge air ratio. https://www.usgbc.org/leedaddenda/10472 Some tips: -Use the single zone option of the calculator, https://www.usgbc.org/resources/minimum-indoor-air-quality-performance-calculator -Use Ez=1, -Make one outdoor air measurement per each AHU, and verify at AHU level. -Try to match the total ventilated area with your total building area.

Andrey Kuznetsov

ESG consultant, LEED AP BD+C

Self Employed

LEEDuser Basic Member

36 thumbs up

Tue, 10/15/2024 - 13:28

What were the comments from the previous submission?

Pulak Goyal

ESD Consultant

GreenA Consultants

LEEDuser Basic Member

0 thumbs up

Tue, 10/15/2024 - 13:37

The previous comments were related to doing the measurements of "fresh air" at each air handler's level, since we had done measurements of "total air flow" and assumed 20% for it to be fresh air, which is common practice for Singapore. But since GBCI commented on measuring only "fresh air", we are now doing measurements at system level fresh air duct. However, in the multiple zone table in the LEED calculator, we still require to fill in "primary airflow" values for each space, even if the system level fresh air is complying.

Omar Elrawy

Green Building Consultant | Researcher

GreenA Consultants

LEEDuser Basic Member

38 thumbs up

Thu, 10/17/2024 - 01:10

Copying from my colleague as she received the LEED comment...
The previous comments were related to doing the measurements of "fresh air" at each air handler's level, since we had done measurements of "total air flow" and assumed 20% for it to be fresh air, which is common practice for Singapore. But since GBCI commented on measuring only "fresh air", we are now doing measurements at system level fresh air duct. However, in the multiple zone table in the LEED calculator, we still require to fill in "primary airflow" values for each space, even if the system level fresh air is complying.

Andrey Kuznetsov

ESG consultant, LEED AP BD+C

Self Employed

LEEDuser Basic Member

36 thumbs up

Wed, 10/23/2024 - 06:12

So you need somehow to demonstrate, that each space recieves at least 20 % of fresh air from the plenum. Even with CFD it's tricky.

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