There are methods for calculating the needed ventilation that takes into account the existing fans and building tightness. I suggest you look for an upcoming training, there are many available, to learn the best approach to determine the need to add additional ventilation. I think the better your understanding, the easier it will be to implement. The Standard is here to stay. I'm not a fan of continuous ventilation, but 20 cfm to 40 cfm is not much air movement and would take over a week to exchange the air in a small house. The challenge seems to be how to get 20 cfm for less than $600.
PS I also tried to find an online resource, but ACI now charges for access to presentations and everyone else seems to be holding back on the information.