Requirements to meet CO2 monitoring

Hi Lise, 

providing PI-diagrams along with specification would be sufficient.

Thanks,

Hello Lise: 

For CO2 monitoring - You can provide project's floor plan showing the densely occupied spaces with CO2 sensors along with specifications. Also, make sure that Ventilation Rate Procedure Calculations provided in EQp Minimum IAQ Performance indicate that CO2 sensors have been installed within each densely occupied space. All the spaces with a design occupant density greater than or equal to 25 people per 1000 square feet need to be monitored by CO2 sensors. 

Hi Lise, density is a different thing than the number of people... You can look at the requirement as let's say 0.025 people per 1 sqf or it would be easier to just calculate the density for each room as a number of people per 1000 sqf. So if you have a room that can be occupied by 2 persons and is 50 sqf, that room would have a density of 40 ppl per 1000 sqf.

Hi everyone. Still, I think the density threshold is not clear.

The measure for defining these spaces is occupant density equal or less than 3.7 square meters per person, or (equal or) more than 25 people per 93 square meters. But it can mean that rooms with less than 25 people are not qualified for adding CO2 censors in them, since the occupancy is small. It seems to me that the criteria is the occupant density and the Occupancy as a total.

I could mean that if a room is more densely occupied than the 3.7 square meters per person, e.g. 2 square meters per person but has 21 occupants,  it is not densely occupied. What does everyone else think?

The requirement requires you to calculate the density based on the 25 people per 1,000 sf definition. Just because the room is not 1,000 sf or doesn't have an occupancy of 25 people DOES NOT mean it doesn't qualify as densely occupied. 25 people per 1,000 sf = 0.025 people per 1 sf. Anything greater than that is densely occupied.

For example, for a room with an expected occupancy of 20 people that is 750 sf you would do 20/750, which equals 0.27. 0.27 is greater than 0.25. Therefore, the room qualifies as densely occupied. 

Does this requirement apply to smaller, densely occupied phone rooms? We have phone rooms that are intended for limited use (quick phone call) with 2-3 people for 70-90 which would exceeded the 40 sf/person requirement. Since it will not be regularly occupied with 2-3 people, I'm wondering if it would need to be included. 

Small phone rooms present a confusing challenge: there's no similar space type in the IAQ Space Matrix to offer clear guidance.  There are a couple of related Interpretations under v2 & v3 that offer some background, but don't specifically address the CO2 monitoring question: 

ID# 1645: Re: Optimize Energy Performance: 

"Re: occupancy-type classification of small spaces used exclusively for making confidential phone calls. These rooms are not intended for use as regularly occupied private office spaces. Also, since these rooms are intended for single occupancy, changes in occupancy will not result in large swings in the heating and cooling loads, as would be true for a break room or conference room. Accordingly, these spaces may be included as part of a larger thermal zone. "

ID# 10263: Re: Optimize Energy Performance: 

"Spaces that would otherwise be considered specialty use spaces but are smaller than 75 square feet, such as the phone rooms referenced in LEED Interpretation #1645, or a lactation room smaller than 75 square feet are not required to have individual active controls capable of sensing space use and modulating in response to changes in space demand." 

You might contact LEED technical customer service (LEED Coach) to get their input. 

I wanted to share that on a recent project undergoing  final LEED review we experienced the LEED reviewer calling out a small 100 sqft conference room with a design of 3 people that did not have a CO2 sensor shown in the design. We were dinged on the review for this space not meeting the credit language. Since it happend to be just one space the project just installed a new BAS thermostat w/CO2 sensor to comply and we were awarded the credit. This is first hand knowledge that LEED does not appear to waive any restrictions for # or people or room size, all that matters is the the occupancy density requirement is met.

Any space with less that 0.025 people/sqft does not need a CO2 sensor and any space greater than than density needs the sensor if applying for this credit with the CO2 sensor option selected.

Is there a spec for minimum requirements for the Co2 Sensor - the only we can find in the reference guide is that it has to be set to the required set points per ASHRAE 62.1-2010 as well it will sound an alarm if levels reach 10% above those set points.

Thank you,

This has been our experience as well - it is just about density, but not size.  Note that I recently got feedback from our engineering team that ASHRAE 62.1 DOES have a limit for requiring CO2 monitoring only in rooms larger than 500 SF, but our experience and reading of the reference guide would indicate that LEED is pushing for compliance regardless of room size (except for lactation rooms and phone booth rooms that David mentions above).

Is this a correct interpretation?

this is how I’m interpreting: http://arco-hvac.ir/wp-content/uploads/2016/04/ASHRAE-62_1-2010.pdf

Thus, maintaining a steady-state CO2 concentration in a space no greater than about 700 ppm above outdoor air levels will indicate that a substantial majority of visitors entering a space will be satisfied with respect to human bioeffluents (body odor).

CO2 concentrations in acceptable outdoor air typically range from 300 to 500 ppm.

x = 700

x + 500 = 1200 ppm is the set point; alarm goes off if it exceeds 1200 by 120 ppm (1200 x 10%).

And x being the variable the MEP would determine based on expected occupancy + level of activity? Based on expected occupancy and level of activity in a lockerroom, the  MEP has determined x = 5000 ppm. Would the set point be 5000 + 500 ppm = 5500 ppm? And alarm would sound if it exceeds 10% of 5500?

A while back I asked GBCI:

"Reference guide requires project teams to 'calculate appropriate CO2 setpoints using methods in ASHRAE 62.1-2010, Appendix C'. Can project teams arbitrarily select the CO2 setpoint? What will need to be submitted to LEED reviewer to demonstrate compliance?"

GBCI response:

"We require that the CO2 setpoints are selected in accordance with Appendix C, but do not require that you upload documentation to confirm how the setpoints were selected. Per the reference guide, it is not acceptable to arbitrarily determine CO2 setpoints. It is unlikely that a reviewer would comment on this issue unless the setpoints are highly unusual."

Also we have successfully excluded 1-person and 2-person 'teleconference/phone pods' from the CO2 sensor requirements.

I am looking for more information on specifications for CO2 monitors as well. Specifically, if it installed in the correct breathing zone, with an audible alarm and with a properly calculated set point, could it be a plug-in unit - that is, not hardwired and not connected to BAS?

Dear Rennick,

It is not a must to connect to BAS.