Described are methods, systems, and apparatus relating to a modular data center. In some embodiments, a modular data center includes one or more data modules. The modular data center includes a network module connected to the one or more data modules, the network module containing equipment for facilitating data communications by the one or more data modules. The modular data center includes a power module connected to the one or more data modules and the network module, the power module containing electronics equipment for conditioning and distributing power to the one or more data modules and the network module. In the modular data center, each module of the one or more data modules, the network module, and the power module comprises: an enclosure defining an internal space; a floor within the enclosure separating the internal space into an above-floor space and a sub-floor space; and a plurality of bays in the subfloor space, each bay of the plurality of bays configured to contain a field-replaceable environmental management component.