Date
Inquiry

Our office has two projects that have been struggling with the requirements of EQ Credit 1. Although very different in type, they have taken similar approaches to ensuring outdoor air delivery to occupants. 1) The first project is a historic renovation of a low-rise residential building with seven units. Fresh air is delivered to the building via an Energy Recovery Unit (ERU) that exchanges exhaust air from the kitchens and washrooms of the units for 100% outside air, which is delivered to fan powered boxes in each unit. The ERU does not have an economizer or an air damper. 2) The second is the renovation of an existing doubled loaded corridor school building, which does not have a central air conditioning system, but instead uses perimeter unit ventilators to provide and heat outside air. The dampers on these units are controlled by CO2 sensors located at the thermostat, and will meet the intent of the credit. However, a few non-perimeter classrooms and offices cannot accommodate these perimeter unit ventilators, and thus has a centrally located unit ventilator that provides fresh air to these particular rooms. This ventilator also uses 100% outside air, and also has no dampers. Our suggested approach to both of these projects is to use a current transducer to monitor the performance and status of the ERU and unit ventilators, instead of using an airflow monitor as the credit requirements call for. The current of the fan varies proportionally to the load so that if the unit is malfunctioning (decreased or no airflow) it will be clearly indicated by the power being consumed by the fan. The CT monitor would then report immediately to building management who would field verify the problem and determine if maintenance is needed. We feel this approach complies with the intent of this credit for the following reasons: 1. The units are designed to run at a fixed airflow rate at all times, never to be affected by damper positions, and thus the only instance where air is not being delivered at the appropriate flow is if there is a malfunction with the unit. 2. Monitoring the outdoor airflow of units that are equipped with outdoor air dampers is useful because the dampers can be adjusted based on outdoor airflow readings. Our systems, however, do not have an outdoor air damper because they use only outdoor air. If we directly measure the outdoor airflow, the unit has no way to respond or be recalibrated to address excess CO2 in the space. Outdoor air flow monitoring could be performed, but the results would be of little use. 100% outside air systems are an important tool in providing fresh and healthy interior environments. We believe that the CT monitoring approach is the best method by which 100% outdoor air units can be measured, and also addresses the intent underlying tenets of the credit. It can be argued that outdoor airflow monitors could also provide this level of measurement (on or off), but it provides no more value or functionality than the CT monitor suggested here in the case of 100% outside air units. Please comment on whether this strategy can be used in achieving EQ credit 1.

Ruling

The CIR is asking if current transducer (CT) monitors are adequate devices to monitor outside air delivery. For a constant volume 100% outside air system similar to the one described by the proponent, the CT approach may satisfy the credit requirement for a direct outdoor airflow measurement device, provided the CT device has been properly calibrated during the installation and commissioning process. Properly calibrated, the CT device would alert the BAS to a change in the fan status, which would indicate a change to the amount of outside air being delivered. In order to satisfy the credit requirements the submittal must show how the CT has been calibrated, and must outline the monitoring sequence. If the system is not 100% outside air, or not constant volume, the CT device would not be adequate. Note that the CT device does not relieve the project of the requirement to monitor room CO2 levels in all densely occupied spaces. -NCv2.2 Requirements state clearly that densely occupied spaces (such as classrooms - mentioned in the CIR) must have CO2 concentrations monitored. Applicable Internationally.

Internationally Applicable
On
Campus Applicable
Off