To be honest with you, in all my years doing this I have never had an inspection where an AHJ checks the exhaust volume. From what I'm told an architect spec'd these fans and that's what's going in. I don't remember the model # but I will get it on monday and I'll post it here. I do know they were purchased from HD by the property management and are fan/light units.
I can't say I know what codes are but basic physics tells me that the properties of convection that naturally ventilate that attic will draw that humidity back into the attic space anyway, so why bother ducting it to the eaves? When it is cold enough maybe you get some of it to condense before it is drawn into the attic is about the only advantage I see, but this is mostly when there is extreme cold of like zero and below temps.
In extreme cold conditions I have been in attics that have frost coating the underside of the roof, that all "rains" down when temps rise enough to thaw it. Similar happens frequently in non insulated steel buildings where someone is using non ventilated portable heaters, water vapor in the exhaust of those heaters condenses on cold steel roof and rains on the inside of building when it does reach melting temperature.It's certainly not the case anymore. I know when I was looking to buy a house in 1986 that one of the properties I looked at was a converted lake house (seasonal) that had the stack vent in the attic. The sheets of plastic everywhere suggested there was an issue, and the inspection report I received indicated that this was a deficiency. I suppose it might not have been much of a problem if the attic was very "leaky" so that there was no buildup of moisture, but I'd think that warm moist air + attic in winter = rain in the space. Maybe if it froze fast enough...
