Commercial and larger residential buildings often have water at various temperatures as a utility. There will be a machine room that has large water-to-water he

Commercial and larger residential buildings often have water at various temperatures as a utility. There will be a machine room that has large water-to-water heat pumps, then a chiller tower on the roof that takes hot water, evaporates some and cools the rest, then returns it to the hot-side heat exchanger. The cold side will circulate water around the building, where it will be used in water-to-air heat exchangers on the room or unit level to cool the building. In most climates, larger buildings need more cooling than heat, but doing the same thing with a hot water system is quite common as well.