Our office building is ventilated with a constant volume AHU and conditioned by VRF system. AHU supplies 100% fresh air to the spaces, while VRF system provides heating and cooling. AHU has heating and cooling coils, however the system is not designed to control the room temperature, it only supplies fresh air with constant temperature.
Because of the modeling software's limited ability, we had to model two separate systems for the same zone; one system for AHU and another for VRF. And we entered the same amount of outdoor airflow rate for both of these separate systems. Therefore, total outdoor airflow rate is actually double-counted in the proposed model.
Recently, we received this review comment: "It is unclear whether the minimum outside air rates (in CFM) were modeled identically in the Baseline and Proposed Case for all zones not having Demand Control Ventilation in the Proposed Case. Confirm that the minimum outside airflow (in units of cfm) was modeled identically in the Baseline and Proposed case using the proposed case rates."
How should we approach this? Should we model the VRF system with zero outside air flow, since it works separately from the ventilation system? Any help would be appreciated.
Marcus ShefferLEED Fellow
7group / Energy Opportunities
5748 thumbs up
July 11, 2017 - 11:54 am
How you model this could vary depending on the software you are using. In some software you need to create a dummy zone. For software specific questions usually the best place to try is either customer support (if it exists) or one of the discussion groups. There are several at onebuilding.org and http://energy-models.com/forum