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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

IEQc1_Densely and Nondensely Occupied Spaces

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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Hi, How do we define nondensely spaces? To satisfy LEED requirements for this credit, do we really need to install CO2 sensors for densely and OA Measurement Device for nondensely? What is the difference between CO2 sensors and OA measurement device? Since nondensely is less than 25 people or non regular occupied space, why do we need the OA device? What are they trying to monitor. Any inputs on this area is highly appreciated. Regards, Susan

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Tue, 06/12/2012 - 12:12

Susan, here are some responses to your questions. I hope they help: 1. A non-densely occupied space is any space with a density of less than 25 ppl/1,000 sf. Divide the space area by the number of people who regularly occupy the space and if that number is more than 40 (sf/p) then it is a 'non-densely occupied space'. 2. Yes we do need both CO2 for densely and OA measurement for non-densely occupied spaces. 3. A CO2 sensor is mounted in the space and measures the CO2 content in the air (in ppm). An OA measurement device is a flow measuring station in the OA duct/intake of the system serving one or more zones. There are other alternatives for certain applications that can be found in the LEED Interpretations database but typically a monitoring station is used. I hope that helps. Remember that for non-dense spaces the intent is to measure the ventilation air to the system to make sure it stays at design airflow.
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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Tue, 06/12/2012 - 21:37

Hi Andrew, Thanks for responses. Just a follow-up question please to understand o of identifying densely and non-densely spaces: 1. For densely occupied space e.g. main entry lobbies with 3,252 SF, should i divide it by 25 and get 130? Or apply 25 ppl/1,000 sf. i have 75 ppl. Is this correct? 2. For non-densely, e.g. breakrooms (130 sf), i divided it by 40sf = 3 ppl. Is it considered non-densely space? 3. What do you mean by " for mechanical ventilation system where 20% or more of the design supply airflow serves nondensely occupied spaces"? Does it mean if i have 3, 280 CFM Design OA intake flow, and 20% of it (656 cfm) is non-densely, then it requires direct outdoor airflow measurement device? Pls. clarify. thanks, susan

Wed, 06/13/2012 - 12:21

Susan, I think for the first two questions you might be thinking about it backwards. Don't try to figure out the space population based on whether or not you think it should be densely populated. You should have the area and population based on the plans and discussions with the owner/architect. Use those two variables to then figure out if it's densely populated or not. As for number 3, you are correct.
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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Wed, 06/13/2012 - 16:06

Andrew, those values are based on the plans, i just want to make sure if my approach/understanding to identify densely and non-densely is correct. thanks, susan
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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Thu, 07/05/2012 - 17:54

Hi, I have question for the following: 1. In reference to above diagram, under OPTION 1 - Mechanical Ventialtion, we can satisfy either/Or for Case 1 or Case 2? 2. Or we need to satisfy both requirements for Case 1 and 2? 3. What do you mean by " for mechanical ventilation system where 20% or more of the design supply airflow serves nondensely occupied spaces"? Does it mean if i have 3, 280 CFM Design OA intake flow, and 20% of it (656 cfm) is non-densely, then it requires direct outdoor airflow measurement device? Then, if its less than 20% (120 CFM) for non-densely we don't need OA measurement device and explain it to narrative? Appreciate clarification of requirement for this credit. Regards, Susan
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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Tue, 07/10/2012 - 18:24

Hi, Can someone help me on this. If my non-densely space is less than 20% design OA intake flow, we don't need to provide OA measurement device? Likewise, my project consists of densely space only and we will provide narrative to support this. Please advice, just want to clarify if both CO2 sensors and OA measurement device are really needed. What is the guideline to determine that CO2 sensors and/or OA measurement device is needed. Appreciate quick assistance. Regards, Susan

Tue, 07/10/2012 - 18:51

Susan, in order for you to be exempt from providing a monitoring station your non-dense space supply airflow will have to be less than 20% of the total airflow. You do not calculate the 20% as if it were only the fraction of required OA. For example, if you have a 10,000 CFM air handler and less than 2,000 CFM serves non-dense space then you do not need a measurement device. This is regardless of the required OA flow to the non-dense space. If you are still confused then please reply with actual design numbers and it will be apparent which situation you fall under.
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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Tue, 07/10/2012 - 20:28

Andrew, so it's not always BOTH (CO2 and OA) to satisfy the requirements? It really depends what is applicable to project as long as it was explained in narrative, right? thanks for clarifying the requirements. This is so confusing. Regards, Susan
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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Tue, 07/10/2012 - 20:36

Andrew, another thing, is there any references or statement that i could use as a reference to justify that my project doesn't require OA for my narrative? thanks, again.

Tue, 07/10/2012 - 20:56

Susan, yes to the first question. As for the second, I never said that anything we discussed justifies not using OA, just not monitoring the OA. If you want to justify not monitoring the OA just quote the verbiage directly from the LEED Reference Guide.
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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Tue, 07/10/2012 - 22:29

Andrew, sorry Im still confused. Could you please explain this statement " Provide a direct OA measurement device capable of measuring the minimum OA intake flow with an accuracy of +/- 15% of the design minimum outdoor air rate, as defined by ASHRAE 62.1-2007 for mechanical ventilation system where 20% or more of the design supply airflow serves nondensely occupied spaces". Does it mean if i have 3, 800 CFM Design OA intake flow, and 20% of it (760 cfm) is non-densely, then it requires direct OA Measurement device, right? What if we've only identified less than 20% (155 CFM) for non-densely space, do we still need to provide OA measurement device? This is what makes us confused. If we need to provide or NOT. thanks, Susan
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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Wed, 07/11/2012 - 01:02

Andrew, if we decided not to use the monitoring OA device due to less than 20% design OA, do we still need to input this to the template? if so, then USGBC will still require us to provide this device or we can just explain it to our narrative? Any suggestion please. thanks - susan

Wed, 07/11/2012 - 11:43

Susan, I think you are making this much more complicated than it is. It's very simple. Follow this process for your situation: 1. Add up the total SUPPLY airflow to all non-densely occupied spaces (for each system). 2. Divide that flow by the total system flow (for each system). 3. If your fraction is less than 0.20 then you don't need to do anything further. If it is 0.20 or higher go to the next step. 4. Provide an OA monitoring system capable of measuring the OA flow (this is the first time you will be looking at OA flow). It's that simple. If you are still confused then please click on my name and go to my website to get my contact info. Call me at my office and I will be more than happy to explain this to you.
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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Wed, 07/11/2012 - 16:47

Andrew, are you saying that we still need to provide OA measurement device for non-densely eventhough we have less than 20% design supply airflow? By the way, we have CO2 sensor for densely spaces. My only concern is for non-densely. I will try to call, i think we have time difference since Im from LA. Once again thanks for being patient with my never ending question. susan

Wed, 07/11/2012 - 16:53

Susan, I don't know if you need it or not because I don't know your actual design numbers. Call my office at 10:15 PST and ask for me.
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susan eguia
LEED Coordinator/Construction Administrator/Business Development
Building Solutions Group, Inc.
LEEDuser Basic Member
47 thumbs up

Wed, 07/11/2012 - 20:48

Our total design supply airflow for all system is 3,955 cfm and for non-densely is 155 cfm only. So, it's less than 20% which means no need to provide OA measurement device for non-densely spaces. thanks, susan

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