"Geothermal" (as they call it here) of that sort can be had in the US, but it's very expensive to install unless you have a large yard (otherwise you have to di

"Geothermal" (as they call it here) of that sort can be had in the US, but it's very expensive to install unless you have a large yard (otherwise you have to dig even deeper) and it's difficult to impossible to recover the cost of the system at sale if you move before saving enough to justify the cost—which itself may be difficult if you consider the opportunity cost of the money, and especially if you take out a loan to do it. The buried hoses/pipes also have a limited lifespan, and will need to be replaced in a couple decades, again at great expense. In short, we don't do stuff like that in the US (at least, not much) because it's often a good way to lose money. Also, I don't know about Spain, but large parts of the US suffer very high humidity through much of the year. Unless you're on an exposed hilltop with a breeze, it's miserable without good air conditioning. Houses aren't build with cooling-via-open-window in mind anymore, either, having fewer and smaller windows than older houses and being built with no thought to positioning the windows and the house itself such that prevailing winds can blow through it. Many interior materials aren't intended to tolerate even moderate temperature and/or humidity swings anymore, and will deteriorate much more quickly under those conditions. So there aren't many days in a year when it's possible to get by with no heating or cooling and just open your windows, either.