Wouldn't it be wiser to get a dehumidifier for this purpose? A cursory glance seems to indicate that it would consume less energy for the task of managing the humidity-levels, when cooling is not required.
>I also wonder what this much reflective stuff might cause as other effects. Would reflecting all your sunlight onto other, non super white houses count as a negative externality? Seems like you'd double your neighbor's AC bill to halve yours.
This would likely be trivial, given the relatively small amount of light that would get reflected onto the building in relation to all of the reflected light - most reflected light would not go towards neighbouring buildings. Plus, they can paint their houses with the same type of paint as well, negating the issue entirely.
Am I correct in understanding that two humidifiers use the same amount of electricity as one AC, making them twice as efficient for the task at hand?
>but separate from that they also increase the temperature because the exhaust has no where to go, defeating part of the purpose of the white roof.
If you're looking to cool and dehumidify, then by all means, use an AC. My question was on the use of an AC while no one was home, ie where the cooling effect would go entirely wasted, and only the dehumidification was valuable, in protecting from humidity-induced damage.
A particular dehumidifier can (of course) be more or less efficient than a particular AC system. But it's probably more efficient, given similar technology, if you want a drier, warmer room.
Hardly ever want that warmer room bit during the Southeast US humid season. So you'd wind up running the AC too, to exhaust the excess heat (including the extra heat from the dehumidifier).