A modular arrangement is provided for housing electronic equipment and associated cooling structure in a data center environment. The modular units provide cooling air on an as-needed basis to individual pieces of equipment by way of individual plenums and associated valves. The units can be interconnected by vertical stacking, in side-to-side arrangements, and back-to-back arrangements. A number of units can be interconnected to form a cell. The cells can be interconnected to form larger units. In this manner, data centers can be configured in any desired arrangement without requiring complicated cooling design.