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If my project is using air handlers that supply 100% outside air at a constant volume, do I still need to install an airflow monitoring device?

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NC-2009 IEQc1:Outdoor Air Delivery Monitoring

How many CO2 Sensors do I need to place in occupied large space?

we have a project of around 20,000 sft and floor height 14 ft. its a textile project. 210 people work there. the space is ventilated by evaporative cooling system. how many CO2 sensors do I need to place for CO2 monitoring?

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Profile picture for user jkmcfarland
John McFarland
Director of Operations
WorkingBuildings, LLC
LEEDuser Expert
39 thumbs up

Fri, 10/30/2015 - 21:40

In my opinion one (1) sensor is sufficient if the space is open (there are no impediments to the diffusion of the gas) and there are no local concentrated point sources of CO2 generation other than the occupants.
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Dylan Connelly
Mechanical Engineer
Integral Group
LEEDuser Expert
342 thumbs up

Fri, 10/30/2015 - 21:45

You don't need any CO2 sensors if it is one big space. You only need CO2 sensors in densely occupied spaces. For units serving spaces that are at least 20% not densely occupied you need to provide outside air flow monitoring to achieve this credit.
Profile picture for user jkmcfarland
John McFarland
Director of Operations
WorkingBuildings, LLC
LEEDuser Expert
39 thumbs up

Fri, 10/30/2015 - 21:50

Hey Dylan! Spot on point. However I seem to remember that if you put CO2 sensors in all spaces served by a system then you can meet the credit requirement without the airflow measurement even if the spaces aren't densely occupied. I used that for a project where we couldn't accurately measure the outdoor airflow. Does that compliance path ring a bell for you?
Profile picture for user dconnelly
Dylan Connelly
Mechanical Engineer
Integral Group
LEEDuser Expert
342 thumbs up

Fri, 10/30/2015 - 21:55

That'd be nice. But I don't think you'd get a good enough sample size in my opinion. CO2 takes a while to mix. I've heard of projects trying to put a CO2 sensor in the main return duct - which would be a better indication of average CO2 - but that hasn't been allowed as a replacement to the measurement by LEED in the past.
Profile picture for user jkmcfarland
John McFarland
Director of Operations
WorkingBuildings, LLC
LEEDuser Expert
39 thumbs up

Fri, 10/30/2015 - 22:00

Yeah, return air is no good because if the outdoor air bypasses the breathing zone it'll give you false sense of over ventilation when the opposite is true. I'm going to personally test the diffusion speed in a large volume space we're working on. Unfortunately I won't be able to do that until late 2016 probably.

Thu, 05/08/2025 - 11:58

Hi John, this is very late but if you still have the data could you share the results on the diffusion speed? 

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