This would work, but is this because you want to model the duct leakage and heat loss without the AFN? If that isn’t important, you could also model the air exchange as transfer air from Room A to Room B, using the ZoneMixing object, (if they are adjacent).
Some care has to be taken since ZoneMixing destroys the conservation of energy principle (only one zone has impact of heat transfer simulated), but this can be accounted for by setting an equivalent Fan:ZoneExhaust flow rate in the sending zone.
Some good discussion on this trick here: