A data center cooling system, comprising: an upper module comprising an air conditioning module; a lower module attached to the upper module and configured to suspend above a floor of a human-occupiable workspace of a data center building that supports a plurality of racks comprising a plurality of heat-generating electronic devices, the lower module comprising a power support assembly configured to provide electrical power to the plurality of heat-generating electronic devices, wherein the lower module comprises at least one side that extends vertically from a ceiling that is attached to the frame of the upper module, the ceiling comprising an aperture to permit airflow between the upper module and a volume defined by the side and the ceiling of the lower module; wherein the volume comprises a portion of a conditioned air plenum that extends from the ceiling of the lower module to a top of the plurality of racks, the conditioned air plenum further defined between back sides of rows of the plurality of racks; wherein the air conditioning module is positioned over the aperture in the ceiling of the lower module and comprises a conditioning module and a fan, the fan positioned over the aperture to circulate a conditioned airflow from the conditioning module, through the portion of the conditioned air plenum, through the back sides of the rows of the plurality of racks, through front sides of the rows of the plurality of racks to the human-occupiable workspace, and back to the conditioning module; and wherein the lower module further comprises a seal to receive a portion of the plurality of racks and seal against an airflow between the human-occupiable workspace and the portion of conditioned air plenum; a roller or slider assembly attached to a frame of the upper module, the roller assembly comprising at least one roller or slider; and a rail assembly attachable to a structure of the data center building, the rail assembly comprising a beam engageable by the roller or slider, when moving the upper module through the human-occupiable workspace on the rail assembly. an upper module comprising an air conditioning module; a lower module attached to the upper module and configured to suspend above a floor of a human-occupiable workspace of a data center building that supports a plurality of racks comprising a plurality of heat-generating electronic devices, the lower module comprising a power support assembly configured to provide electrical power to the plurality of heat-generating electronic devices, wherein the lower module comprises at least one side that extends vertically from a ceiling that is attached to the frame of the upper module, the ceiling comprising an aperture to permit airflow between the upper module and a volume defined by the side and the ceiling of the lower module; wherein the volume comprises a portion of a conditioned air plenum that extends from the ceiling of the lower module to a top of the plurality of racks, the conditioned air plenum further defined between back sides of rows of the plurality of racks; wherein the air conditioning module is positioned over the aperture in the ceiling of the lower module and comprises a conditioning module and a fan, the fan positioned over the aperture to circulate a conditioned airflow from the conditioning module, through the portion of the conditioned air plenum, through the back sides of the rows of the plurality of racks, through front sides of the rows of the plurality of racks to the human-occupiable workspace, and back to the conditioning module; and wherein the lower module further comprises a seal to receive a portion of the plurality of racks and seal against an airflow between the human-occupiable workspace and the portion of conditioned air plenum; a roller or slider assembly attached to a frame of the upper module, the roller assembly comprising at least one roller or slider; and a rail assembly attachable to a structure of the data center building, the rail assembly comprising a beam engageable by the roller or slider, when moving the upper module through the human-occupiable workspace on the rail assembly.