An apparatus includes an enclosure defining an interior space and at least one server-rack port configured to engage one or more of racks such that one or more servers installed in each rack are contiguous to the interior space. The enclosure is inside of a room and includes at least one stability control unit at the bottom of the enclosure. Each server includes a fan that draws air from the interior space into the server and expels the air outside of the enclosure into the room. The apparatus also includes a mixing chamber that is contiguous to the enclosure. The mixing chamber includes a first set of one or more dampers that are contiguous to natural air outside of the room and a second set of one or more dampers that are contiguous with air in the room.