A qanat can be little more than a shaded pond. It doesn't have to be underground. Air around it is cooled, then drawn by the wind tower through the house.
OK, that makes sense. All you need for that is a source of water and a low-humidity environment. I guess well pumps use less energy than air conditioners?
Why isn't this considered as a solution more often? Is it just because construction costs go up, or for reasons of culture and habit? It seems like this is absolutely the best approach for stabilizing temperatures in both hot and cold climates. Might not work well in a place with a lot of ground water, I guess, but in general it seems like a win. Reduces building profiles, as well.
While I've read enough Asimov to believe that the future is underground, I'll also be the first to admit that the lack of windows is a major problem with the system. You both lose natural light and the cooling air currents provided by the wind.
Well I didn't mean all the way underground -- I think you'd get substantial benefits from going three-quarters down on the ground floor. If there's only one floor, skylights do the trick. For multiple stories, high windows, and then fans circulating air between floors. Hmm, I guess this is getting a little expensive after all...