I noticed Ben's comment below from February 10th,
"Also, if the CO2 sensors are located in the return duct, the review team will likely request justification for how those sensors are accurately accounting for the CO2 in the breathing space of the occupied spaces."
Funny, I just got that exact comment back last week. I'm wondering, Ben, what type of justification could a team provide in this scenario? If we've already set up the calculations and testing to reflect the scenario where the potentially critical zones are fully occupied and the fans and outside air dampers are set to the lowest point, haven't we already demonstrated that the AHUs can push enough outside air to satisfy ASHRAE 62.1?
It seems this comment relates to IEQc1.2, which we are not pursuing.
Hannah Bronfman
Senior Associate99 thumbs up
March 11, 2014 - 4:32 pm
Hi Katie
I think the review team is just asking you to confirm that you are aware that the CO2 sensors are in place and that you understand the implications that the sensors have on your system and the associated OA flow rates. But more so, they are testing you to see if you have adequately accounted for the sensors during testing.
So I think all you need to do is provide a narrative confirming that your approach took into account the above considerations and then include the narrative you began regarding your specific "calculations and testing to reflect the scenario where the potentially critical zones are fully occupied and the fans and outside air dampers are set to the lowest point." Use enough detail so that the review team is aware of your understanding of the implications.
Good luck!
Ilona Johnson, PE, CEM, LEED AP
AssociateLilker EMO Energy Solutions
8 thumbs up
March 29, 2014 - 9:15 am
I saw a similar comment on a LEED CI project, and the reviewer stated that CO2 sensors in the return duct do not meet ASHRAE 62.1. They were concerned that CO2 sensors in the return duct report an average CO2 level, but do not report the CO2 concentration in worst case zones. The problem is that a return CO2 sensor could report a CO2 concentration that is lower than the space concentration in a densely packed conference room. If the building automation system reduces the outdoor air supply based on the return CO2 sensor, it could be starving the conference room of required outdoor air.