Nah, you misunderstood, I was asking if you're venting the room during lights out is all, not that the fan is heating the room. My bad though. So it's safe to say you're cooling the room during lights off? If that's the case a portable AC should be ok. And no, an AC doesn't cool with moisture, AC units help remove moisture from the air. I don't know much about the whether in SA, but when it's both cold and rainy here, we use the AC with Heat in our cars to help get rid of fog. Blowing the damp air through the condenser removes moisture. All AC works the same way, even the one in your fridge and freezer.