Systems and methods are provided for cooling an electronics rack and a computer room from a single unit, which includes a heat-generating electronics subsystem across which air flows from an air inlet to an air outlet side of the rack. First and second modular cooling units (MCUs) are associated with the rack and configured to provide system coolant to the electronics subsystem for cooling thereof. System coolant supply and return manifolds are in fluid communication with the MCUs for facilitating providing of system coolant to the electronics subsystem, and to an air-to-liquid heat exchanger associated with the rack for exclusively cooling air passing through the rack, as well as conditioning the ambient air of the computer room. Such cooling is exclusive of an outside-of-rack conditioned air unit.