We are working on certifying a building that has demand-controlled ventilation (DCV), controlled by CO2 sensors. A dedicated outdoor air unit (DOAU) supplies 100% OA to fan powered induction units (FPIUs) that ventilate specific zones. Conference rooms have their own CO2 sensor which modulates the OA flow for that FPIU. Private and open offices usually have several FPIUs that are all controlled by a single CO2 sensor located in the open office breathing area. Other single zone spaces have occupancy sensors that modulate flow on or off.
1) To demonstrate compliance with LEED IEQp1, what documentation must be shown for DCV systems? Can we just show our DCV sequence of operation for each ventilation zone (i.e., for each CO2 sensor) is based on equation A-H of the ASHRAE 62.1-2007 user manual and perform the building outside air component (Rb) calculation for each space to demonstrate the required minimum OA value of the DCV sequence?
2) Does LEED accept several zone level systems (FPIUs in our case) to be controlled based on one CO2 sensor if the zone systems are in the same ventilation zone and the CO2 sensor is in the breathing zone?
3) During the period of performance, should a population count be done at the time of measurement to verify the OA flow is adequate or is a measured flow matching an accurate DCV command sufficient?
Ben Stanley
Senior Sustainability ManagerWSP - Built Ecology
LEEDuser Expert
250 thumbs up
December 20, 2017 - 7:06 pm
Hi Robert,
A few thoughts on your questions.
1. To demonstrate compliance with the prerequisite in this case, you'll need to show that the system provides, at minimum, sufficient outdoor air to satisfy the area-based component of the VRP calculations when CO2 levels are below the setpoint. So, instead of maximum occupancy, you'd set the occupants to zero in the VRP calculations to determine this value. In addition, you'll need to demonstrate that the measured outdoor air flows meet the required ventilation rate under the condition of max occupancy during typical operations (when the CO2 levels rise above the setpoint).
2. The approach with a single CO2 sensor controlling multiple FPIUs should work, assuming that the FPIUs serve a common ventilation zone.
3. The VRP calculations will have to account for actual occupancies expected during typical operations.