IEQc1 and IEQc2

No, you won't lose EQc2 if you also comply with EQc1. EQc1 requires an alarm when the CO2 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 spaces 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