The dripping is from condensation. Right now in Atlanta, the dew point is 24°C. That means if I cool my house to reach that temperature, the humidity inside wil

The dripping is from condensation. Right now in Atlanta, the dew point is 24°C. That means if I cool my house to reach that temperature, the humidity inside will be 100%… perfect for mold and terrible for everything else. Using an open water cooling mechanism would work in hot and dry climates, but then again those are the areas where water is a lot more precious and you don't want to waste it through evaporation. (In a highly humid environment, evaporative cooling does not work because the water has nowhere to go.) A heat pump is the only mechanism that works for this kind of climate. The exchange could be improved by using water or the ground to absorb the heat, but those solutions are way more expensive to install and can have environmental concerns of their own. I'm generally impressed with the energy initiatives in Germany and have been following the Passive House movement for a while, but some technologies only work for specific climates or only in one direction.