No matter how hard we try to explain, some customers will not accept the fact that concrete foundations become warm during the peak of the summer months. The foundation radiates heat and moisture into standard below grade wine cellars. When the concrete is at grade level, the problem is dramatically compounded. It would require a huge, wasteful, and expensive cooling system to dissipate that heat (one which we have no interest in making or selling). During summer months your concrete floor is the most important surface to insulate. In fact it should ideally have at least 2" of foil backed urethane foam at a minimum. Cement floors are great in the winter when you do not even need a cooling unit. However, summer months are when you need the power of a cooling unit and that means you need a well-insulated concrete floor. By the way, in North America below grade cement floors generally reach close to or above 70ºF by the end of summer. Imagine a small cooling unit trying to cool down a giant slab of cement from that temperature level, constantly radiating heat. In these circumstances the condensate in cooling units will overflow and the units will run continuously. Under these conditions, units have a high failure rate.
One additional point : Cement floors tend to be more significant than bare uninsulated walls (also bad) because of the ground water effect. Being closer to the ground water, the floor acts as a wick for the water which ends up in your cellar. Water puts a heavier load on your cooling unit than high temperatures, and severely diminishes the efficiency of the cooling system . To put it simply: Arizona at 110ºF and 9% R.H. is a better environment than Florida at 90ºF and 80% R.H. You will need less cooling power in Arizona.