NC 2009 IEQc1: Outdoor Air Delivery Monitoring

Maria,

In order for a room designed for two people to require a CO2Carbon dioxide sensor it would need to be 80 sq ft or less. Just want to make sure we're clear on that point first.

If the spaces are designed as small meeting rooms and they meet the criteria above, then yes they do need CO2 sensors.

If the spaces are offices for one peron (who will regularly occupy it) and that person occationally meets with others in their office than they do not need CO2 sensors.

Basically it's about the intended use of the space.

That being said, CO2 sensors are relatively inexpensive and a good best practice.

Thank you Emily!

Maria,
I ran into a very similar situation. See my comment on June 27th. I don't have an answer yet, as the project is still waiting for LEED review comments. However, we did do a quick energy saving ROI calc and found it would have taken over 100 years! to recoup the costs of installing all those CO2Carbon dioxide sensors. The client decided not to put in the C02 sensors.

Dylan
That is very interesting! (I didn't realize that your question was about the same thing). Please do let us know how it turns out. I also have a large amount of smaller “chat-rooms”. Hasn’t anybody tried a CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide? I think that less than 150 sf or 10 people is quite a reasonable limit.

Is that fan coil unit constant volume? 100% OSA? Or variable volume with minimum OSA? Hard to say without more information. But, it sounds like the outdoor airflow device on the fan coil is sufficient.

So whether you have 5 people in the room or 500 people in the room the air is still the same constant volume, say 10 air changes per hour (and I made that up)? Wouldn't you need more fresh air for 500 people than the 5? How would the system be able to respond to the change in occupancy if it is fixed? These are the questions you'll want to answer if you don't install the flow meters. Reread the credit intent and ask if the engineer's solution is meeting that intent.

Kristin,

Can you install outdoor air monitoring devices in each space? As opposed to at the PTHP units? I do not think only installing CO2Carbon dioxide sensors will be enough to earn this credit, since one of the requirments is to montor outdoor air flow. 

Anyone else have experience with this?

i have the same question -- if it's an Outdoor Airflow Monitoring Device, not CO2Carbon dioxide, what in the world is supposed to go in that column??

This column does not appear on version 4 of this LEED Online form, so it seems as though it was an error. You can ask GBCI to update your form.

Under "Implementation" in the LEED manual they do specifically ask for air flow measuring devices. A lot of units come with an air flow measuring devise, but if you have one of the following types of units you may not need one:

Is the equipment constant volume? If so, then you are set.

If you have a VFDA variable frequency drive (VFD) is a device for for controlling the speed of a motor by controlling the frequency of the electrical power supplied to it. VFDs may be used to improve the efficiency of mechanical systems as well as comfort, because they use only as much power as needed, and can be adjusted continuously. AHU1.Air-handling units (AHUs) are mechanical indirect heating, ventilating, or air-conditioning systems in which the air is treated or handled by equipment located outside the rooms served, usually at a central location, and conveyed to and from the rooms by a fan and a system of distributing ducts. (NEEB, 1997 edition) 2.A type of heating and/or cooling distribution equipment that channels warm or cool air to different parts of a building. This process of channeling the conditioned air often involves drawing air over heating or cooling coils and forcing it from a central location through ducts or air-handling units. Air-handling units are hidden in the walls or ceilings, where they use steam or hot water to heat, or chilled water to cool the air inside the ductwork., then you may be able to prove you have the appropriate airflow If you have a minimum airflow damper on the unit.

Are you planning to apply for an ID or exemplary points for your 100% outisde air system? We have a similar system and are wondering if we could possibly get an ID point.

LEED Interpretation #2099 addresses using CTs (circuit transducers providing fan status) for constant volume and 100% OA systems as an alternative to the airflow station to comply with this credit. This CIR is from LEED NC V2.2, but may be applied to BD+C V3.0 projects.

There are no exemplary performanceIn LEED, certain credits have established thresholds beyond basic credit achievement. Meeting these thresholds can earn additional points through Innovation in Design (ID) or Innovation in Operations (IO) points. As a general rule of thumb, ID credits for exemplary performance are awarded for doubling the credit requirements and/or achieving the next incremental percentage threshold. However, this rule varies on a case by case basis, so check the credit requirements. credits for EAP1, C1 or C2.

Dylan,
There aren't any published CIRs or addenda so far that have addressed this question, though inquiry #1625 has some similarities. In that instance GBCI did not allow an exception.

You'll probably need to submit a CIR for your situation to get a clear answer - you might consider proposing that the Title-24 language provides greater clarity of when a small space should or should not be considered "densely occupied" since it looks at more variables - room size and design occupancy - instead of just the 25 per 1000 sf number.

This is a great question! We have a similar situation for a project right now. If you do submit a CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide, would be very interested in hearing the outcome!

Dylan,

Did you submit the T24 reference for your project LEED submittal for IEQc1? I am in a similar situation for one of our projects. I'm just wondering how this turned out for your project.

Norma, those areas do required CO2Carbon dioxide sensors according to the credit requirements. This should help ensure adequate ventilation in those spaces.

What part of the credit requirement requires CO2Carbon dioxide sensors not enclosed by walls? Where is the line drawn what is and is not included in a space?

The intent of this credit is to maintain occupant well being. There are no exceptions that I know of for residential units. If the OA is supplied directly to the individual units in the dorms then you need to either install an air flow monitor OR per CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide 3/15/2007 meet the requirements by installing a CO2Carbon dioxide sensor in lieu of an air monitoring system.

No, you won't lose EQc2 if you also comply with EQc1. EQc1 requires an alarm when the CO2Carbon dioxide level varies by 10% from the design values and an alarm when the OA is 15% below the design values. The design values need to be calculated in accordance with ASHRAE 62.1 and the OA sensor needs to have an accuracy of +/- 15%. If you look at the description of the OA Flow Monitoring under paragraph 4 of the reference guide for EQc1 it states the measurement device must detect when the system is 15% below the design minimum OA rate, additional OA is generally a good thing.

So to achieve both credits you'd need to:
1.) Calculate and design the HVAC to provide the minimum ventilation rate per ASHRAE 62.1 (EQp1 and EQc1)
2.) Calculate and design the HVAC to provide the 30% additional ventilation rate compared to EQp1
3.) Install CO2 sensors in densely occupied spacesDensely occupied spaces are areas with a design occupant density of 25 people or more per 1,000 square feet (40 square feet or less per person). that detect and alarm when CO2 levels vary by 10% above design levels
4.) Install an OA measurement device that alarms if OA falls 15% below ASHRAE 62.1 minimum ventilation rate

Also any reccomendations for a brand/model of CO2Carbon dioxide sensor that would meet the needs for the credit?

Hi Nelina, the most complete way to answer your questions is to ask you to log in to LEEDuser as a member and read the extensive action steps, tips, and best practices we show above, in the Checklists  tab. The GreenSpec products box in the right sidebar shows several options for compliant products.

If you're not yet a member and you decide to join now, but decide it's not worth it, we'll give you a full refund.

Even if there is no dilution of the return air from other return ducts before the CO2Carbon dioxide sensor's location in the duct, LEED does not allow installing CO2 sensors in the return duct. (There is a CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide under LEED NC 2.2 (6/27/2008) that confirms the same.) We cannot find any exceptions to this.
If a space does not have well mixed air (which is possible for various reasons) then the CO2 concentration may not be uniformly distributed. In such situations, locating a CO2 sensor in a return duct may not depict real conditions in the breathing zoneThe breathing zone is the region within an occupied space between 3 and 6 feet above the floor and more than 2 feet from walls or fixed air-conditioning equipment. (AHSRAE 62.1–2007).

Thanks for you reply, is there any criteria or standard which mention how much CO2Carbon dioxide sensor should be placed in a breathing zoneThe breathing zone is the region within an occupied space between 3 and 6 feet above the floor and more than 2 feet from walls or fixed air-conditioning equipment. (AHSRAE 62.1–2007). what i feel that placing one CO2 sensor for a breathing zone of say 200 person will also not give accurate measurement of CO2 due to non uniform distribution of occupancy?

It is at the designer's discretion to determine the quantity and location of multiple Co2Carbon dioxide sensors. It depends on configuration of the space , distribution of population etc. There is some guidance in Appendix A of ASHRAE 62.1 but it does not address the quantity of Co2 sensors required in such spaces.

Yes, based on the addenda your assumption is correct.

The document or the addenda does not state that you require CO2Carbon dioxide monitoring "in addition" to air flow measurement if your project consists of a densely occupied space only. (with reference to LEED 2009 for commercial interiors inc addenda 7/19/2010)

For this and the comment immediately below, seems like there are two separate questions here:
1. Is the wording of the graphic correct for Option 1, Case 2 (projects with some non-densely occupied space);
and
2. For a building that ONLY has densely occupied spacesDensely occupied spaces are areas with a design occupant density of 25 people or more per 1,000 square feet (40 square feet or less per person)., is outdoor airflow measurement required?

Re: Question 1:
The graphic has some small wording errors in simplifying the requirements. The graphic uses "Option 1," "Case 1," "Case 2," for Mechanical situations and "Option 2" for Natural Ventilation, but the Reference Guide only uses "Case 1" for Mechanical and "Case 2" for Natural ventilation. This may cause a little confusion if looking at both the diagram and the book, but shouldn't change any of meanings.

The credit language defines the one mechanical scenario as when "20% or more of the design supply AIRFLOW serves non-densely occupied spacesNon-densely occupied spaces are areas with a design occupant density of less than 25 people per 1,000 square feet (40 square feet or more per person)."" rather than the diagram's "at least 20% of the SPACE is not densely occupied." Though again the wording is slightly different, the intent is essentially the same: any project with at least a moderate portion of non-densely occupied spaces, such as open office, needs to have outdoor airflow measurement.

Re: Question 2:
Both the LEED Interior Design & Construction Addenda (CI) AND the Building Design & Construction (includes NC) Addenda have several similar changes posted July 19, 2010 that change the wording of Case 1, Mechanically Ventilated Spaces and the footnotes at the bottom of the pages (435 in BD&C, 297 in ID&C). It took me a few minutes to sort out the changes, and it's awkward enough to be unclear.

In short, we reverse the numbering of the footnotes, and add a footnote number 1 at the end of Case 1, paragraph 1's last sentence "... 3 and 6 feet above the floor. (1)"

This inserts the wording "CO2Carbon dioxide monitoring is required in densely occupied spaces, in addition to outdoor air intake flow measurement."

So, for three scenarios, what's the requirement? Here's my impression:
a) A building with all open offices, and no densely occupied spaces: outdoor air intake measurement are required, but not CO2 monitors.

b) A building where half the supply air serves open offices, and half serves densely occupied spaces such as meeting rooms: BOTH outdoor air intake measurement AND CO2 monitors are required, since this is a combination of Case 1 paragraphs 1 and 2.

c) A building with ONLY densely occupied spaces (such as an assembly hall) or with MINIMAL non-densely occupied space: This is where it gets confusing.

When you check the LEED Online credit form for NC IEQ 1, if you indicate that your project only has densely occupied spaces, you only are asked to document the CO2 monitors, and not any outside air measurement devices.

Then why the addendum change? Is it saying (one) ALL densely occupied spaces in ANY building have to have CO2 monitors AND outdoor air intake measurement? Or is it saying (two) IF you have a building with both dense and non-dense spaces (that meet the 20% threshold) THEN the densely occupied parts need CO2 monitors AND outdoor air measurement. The credit form suggests the answer (two) is correct, but the addendum implies but doesn't clearly suggest answer (one).

Sheesh, it's hard to be clear, ain't it?

Yes it is rather muddied, it was my understanding that CO2Carbon dioxide monitoring would help to reduce a building's emissions, due to the fact that the mechanical ventilation system would only be supplying enough fresh air to ensure the correct CO2 levels within the occupied space (using variable speed fans). By keeping the CO2 levels within the design parameters comfort of the occupants could be ensured, and due to the nature of the ventilation system it would not seem prudent to be measuring the air intake due to the fact that the flowrate would be constantly altering to meet the required design CO2 levels, as well as attempting to reduce the amount of energy and subsequent carbon emissions required to achieve this. It is simple enough to say there will be 300 people in the occupied space give each occupant 12 litres per second of fresh air (which must be heated, cooled and dehumidified etc to meet the design supply conditions), however is this the correct approach? CO2 monitoring (if implemented correctly) should help to stop over ventilation of a space and excessive energy use caused by conditioning the excess air unnecessarily. The only time that the outdoor air would be measured would be during the initial commissioning of the system; this would ensure that the system would be capable of meeting the maximum demand of the occupied space. This type of ventilation strategy allows fresh air rate to be adjusted in order to meet the immediate needs of the space. Why would we need to monitor the outside air if the CO2 levels are acceptable? In my humble opinion we should be concentrating on ensuring that we keep our building CO2 emissions to a minimum, whilst also of course ensuring occupant comfort.

I tend to agree with you, Douglas, but I did read the following counterpoint in the 'checklist' section for this credit, which may be the reason for requiring airflow measurement devices in non-densely occupied spacesNon-densely occupied spaces are areas with a design occupant density of less than 25 people per 1,000 square feet (40 square feet or more per person).".

"CO2Carbon dioxide sensors do not provide the same benefit in non-densely occupied spaces as they do in densely occupied spaces. It is important to remember that CO2 sensors measure only CO2 generated by human occupants and they are typically not a good way to indicate indoor air quality in non-densely occupied spaces. CO2 monitors cannot replace outdoor air monitors and are often incorrectly preferred because they are less expensive than outdoor air delivery monitoring."

My interpretation is that CO2 is a proxy for other potential air pollutants in addition to CO2, but that it is only a reliable indicator of air quality in densely occupied spaces.

On a related but slightly distinct subject, is it possible to install CO2Carbon dioxide monitors in lieu of airflow measurement devices in non-densely occupied spacesNon-densely occupied spaces are areas with a design occupant density of less than 25 people per 1,000 square feet (40 square feet or more per person)." under LEED NC 2009? Multiple Credit Interpretations established that this was permissible under LEED NC v2.2 (to read some, visit https://www.usgbc.org/leedinterpretations and search for 'CO2'), but it is not clear to me whether this is still the case under the 2009 rating system.

Anders, your above interpretation is correct I think that the CO2Carbon dioxide monitoring only applies for densely occupied spacesDensely occupied spaces are areas with a design occupant density of 25 people or more per 1,000 square feet (40 square feet or less per person). and, as stated, in these instances I believe that CO2 monitors can be used in lieu of fresh air monitoring. Thanks for the link to v2.2 info.

I'm a bit confused about the requirements of this credit, given the way that the 5/9/2011 document addenda reads, and the current template form. In my original LEED 2009 reference guide there's a footnote #2, "CO2Carbon dioxide monitoring is required in densely occupied spacesDensely occupied spaces are areas with a design occupant density of 25 people or more per 1,000 square feet (40 square feet or less per person)., in addition to outdoor air intake flow measurement." Footnote #2 is referenced in the original guide in the Naturally Ventilated Spaces section (Case 2). Apparently a subsequent addenda copied an identical footnote and it was referenced in the Mechanically Ventilated spaces section (Case 1). Now, in the latest addenda document, it appears that both footnotes have been entirely stricken, and if I go to the USGBC website and look at the information page for this credit, there's just the one footnote about ASHRAE addenda (which has always been there). This would seem to indicate (to me, at least) that if you have a ventilation system with 20% or more of design airflow serving nondensely occupied spaces, then you'd need an airflow measurement device, but if you have a densely occupied space in that area (say, a conference room), then CO2 sensors aren't required.

The template form, on the other hand, seems to want CO2 sensors in all densely occupied spaces, without reference to whether there's an airflow measurement station or not. Does anyone have any insight as to what the actual requirements are?

Andrew, good point. I'll fix this.

Yet the diagram at the top reflecting the credit language as clear as usual. please correct me; CO2Carbon dioxide sensors required in case of mechanical densely occupied spacesDensely occupied spaces are areas with a design occupant density of 25 people or more per 1,000 square feet (40 square feet or less per person). & naturaly ventilated spaces.
outdoor airflow monitors required only for mechanical ventilation systems where 20% or more of the design supply airflow serves nondensely occupied spaces.

Ashraf, I think you have it right.

Having read a number of comments on the issue, most of them conflicting, am I right in thinking that the diagram at the top of the page is in fact correct, in that it shows that if you are using option 1 case 1 for your project then only CO2Carbon dioxide monitoring is required. A comment above refers to an addenda to the LEED 2009 for commercial interiors document, as far as I can ascertain the LEED criteria is as follows; Monitor CO2 concentrations within all densely occupied spacesDensely occupied spaces are areas with a design occupant density of 25 people or more per 1,000 square feet (40 square feet or less per person).. Provide a direct outdoor airflow measurement device capable of measuring for mechanical ventilation systems where 20% or more of the design supply airflow serves nondensely occupied spaces. This would indicate that CO2 monitoring takes precedence in densley occupied spaces and as such no air flow monitoring is required, however in nondensley ocupied spaces there is a need for air flow verification. Is this assumption correct?

This is just referring the 62MZCalc.xls. Note that there is a licensed professional exemption path for this credit that allows for reduced documentation requirements.

Where can this be found?

If you are registered for a project on LEEDOnline.com.
Go to "Score Card" then "IEQp1." Then in the top right corner you will see "Quick Links" - click on Credit Resources. From there you can download the file 62MZCalc.xls.
You may also be able to click on this link:
https://www.leedonline.com/irj/go/km/docs/documents/usgbc/leed/config/credit_pool/2009/one_off/V03/ci/ieq/ieqp1/resources/USGBC%20LEED%2062MZCalc%20(May%202011).xls

The link got cut off - copy and paste this in pieces.
https://www.leedonline.com/irj/go/km/docs/documents/
usgbc/leed/config/credit_pool/2009/one_off/V03/ci/
ieq/ieqp1/resources/
USGBC%20LEED%2062MZCalc%20(May%202011).xls

You can also click here.

Hi Jean, we have some discussion of this in the Bird's Eye View and Checklists sections above.

You'll be required to include a CO2Carbon dioxide sensor in each unit, which for many projects won't be cost-effective. I don't know of a cost-effective way to get around this. What are your thoughts on this approach?

A question slightly related to the above.. the residential unit typically get its make-up air from operable windows plus pressurized corridors, plus neagtive pressure created by bathroom fans and kitchen exhaust which may or may not always be used(from CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide 3/15/2007). It also uses a VRF system. Each unit has multiple spaces such as 3 bedrooms, living and dining area (total area is around 1800sf, 6 or less persons per unit). For this case, is one CO2Carbon dioxide sensor per residential unit enough to satisfy the credit?

Peter, I don't have an answer for you, but I do have a question of clarification. Where would you be putting the monitors if you were following the correctional facility guidance (if not 3'–6' above the floor)?

This is a great question that really speaks to the intent of this credit. I'm at a presentation right now with John Straube, P.E., and I put this question to him at the lunch break.

He told me that you need the monitoring because without it, the engineer actually cannot know a) what rate the fan is actually operating at, and b) how much air it is actually delivering, when accounting for friction and other operational peculiarities.

It is such a common issue that a system is "supposed" to be delivering a certain quantity of air and just isn't. This credit is a good check. A thermistor is a good way to implement it.

Look at LEED Interpretation #2099 which addresses using CTs (circuit transducers providing fan status) for constant volume and 100% OA systems as an alternative to the airflow station to comply with this credit.

If you have a constant volume system AND a 100% Direct OA system, you don't need the air station if you have fan status. However, it must be BOTH 100% OA and Constant Volume.

This CIR is from LEED NC V2.2, but may be applied to BD+C V3.0 projects. See the applicability tab for this Interpretation in the database.

this link only work for Version 2.2 and not for V3