Thrash, how interesting that you mention that...I was wondering the exact same thing! The inefficiencies involved in the inevitable loss of energy in the refrigerant lines strung over hundreds of feet for lower units, even if thoroughly and properly insulated, would be huge! I'm a civil engineer, though, not a mechanical engineer, and, this must be the best way to do it, or else some other system would be in place. One thing I'm considering is that they wanted units to be equipped with "individual", "owned" units. A building-wide chiller and boiler system has to be a more efficient way to do it.