Question-and-Answer Resource for the Building Energy Modeling Community
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To answer your question, it largely depends on several factors that would reduce your opportunity for energy use reduction:
1) You have a constant or nearly constant need for the same quantity OA.
2) Your need for OA quantity changes, but there aren't controls in place (in the design AND in your model) that allow the quantity of OA to be reduced at times.
3) The OA quantity is small and the resulting DOAS fan motor horsepower is small. Although the total magnitude of savings may be little, a VFD may still provide an ROI in this case.
4) You have many economizer hours where it is beneficial to take a larger quantity of outside air, even though the OA requirement is less.
@Julien Marrec - there still could be a small energy benefit if the VFD could be used for airflow balancing, or to adjust pressure to maintain constant airflow over time while filters loaded and then were replaced. Large motors that start and stop frequently may also benefit from use of a VFD at startup as an operational (non-energy) measure.
