CO2 sensors applicable to non regularly occupied space?

That's correct, no CO2 sensors in non regularly occupied spaces like lunch rooms. As noted in the LEEDuser checklist for this credit, CO2 sensors are actually a poor air quality measurement tool in places that are not densely occupied because they are designed to measure CO2 generated by humans. Better to ensure delivery of fresh air through direct monitoring of OA.

Helena,
I am not so sure that break rooms/lunch rooms are excluded from this credit (or even should be considered non-regularly occupied).
The credit language does not specifically say "regularly occupied" anywhere, but rather says "Monitor CO2 concentrations within ALL densely occupied spaces."
IMO you would be pushing your luck on this credit if you don't provide CO2 sensors in break rooms/lunch rooms.
Yetsuh,
Yes, CO2 sensors in places that are not densely occupied are not required, but the question was regarding densely occupied spaces that are only occasionally occupied.
The CO2 sensors used in densely occupied spaces for this credit need only generate an alarm and not necessarily be used to dictate the amount of OA.

I happily defer to the engineer among us. We have excluded these types of spaces previously without a problem but, per your reading, it is probably best for Helena not to push her luck.

All experiences and opinions are welcome!
I think this regularly occupied space business could use a clarification from the LEED folks. We wouldn't exclude break rooms/ lunch rooms from our Ventilation Calcs, but it does seem to not fit into the definition of:
"Regularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building."

To be safe use the one-hour rule, intended for schools, but applicable to any LEED project.

LEED 2009 BD+C Reference Guide
> IEQ Overview
> Compliant Space Types for Indoor Environmental Quality Credits
> Other Regularly Occupied Spaces

"This category includes all nonlearning spaces that are used by occupants for 1 or more hours per day to perform work-related activities: ...."

Included in the list above are: kitchen and staff lounge.

Hi everyone,
I think Dylan is exactly correct that the credit makes no exception for densely occupied areas if they are not regularly occupied. In fact, these are the best candidates for monitoring CO2 in a demand controlled ventilation strategy. Since the design outdoor air is only needed when the space is fully occupied, there is a likely a huge opportunity to save energy while ensuring adequate ventilation when the space is either unoccupied or partially occupied. Care should be taken in determining the proper CO2 setpoint (note, it's likely not 1000 ppm or even 700 ppm above ambient - refer to Appendix C of ASHRAE 62.1-2007). Also remember that you cannot reduce the ventilation rate below the "building" component (Ra in Table 6-1) except when the air handling system is in the "unoccupied" mode. Other considerations include using accurate CO2 sensors, calibrating them at regular intervals and making sure the modulating outdoor air dampers are well-maintained.

Perhaps the irony of this credit is for densely occupied spaces that are regularly occupied at design rates, then Yetsuh is absolutely correct that the best means of ensuring a ventilation rate that meets 62.1 is to directly measure the outdoor airflow and compare the measurement against the design setpoint. A CO2 sensor in this case really doesn't help you much, but that's not how the credit requirement is worded. Maybe we can change that in the next version.

So in summary, stick to your plan and put the CO2 sensors in the lunch/break rooms. Consider using demand controlled ventilation (DCV) strategies to save energy. If done correctly, we can have our cake (good IAQ) and eat it too (save energy)!