Roof air conditioning units (ACUs) are the engine behind cooling your home or business—no matter what the temperature outside is. But what is an ACU exactly and how does it work? Understanding a little of the science behind roof ACUs will give you a better idea of how this equipment works and why it’s so important for maintaining a comfortable interior temperature. From how different components function to determining which type best suits your building, here is a comprehensive look at the official business definition of roof AC units.