Grey space

Grey space is the area of a data center given over to mechanical and electrical support infrastructure — generators, switchgear, UPS and battery rooms, chiller plant, pumps and CDUs — as opposed to white space, the raised-floor or slab area that actually holds IT racks and generates rent. Grey space doesn't bill by the rack, but it is what makes the white space usable: redundancy level (N+1 versus 2N), backup runtime and cooling capacity are all functions of how much grey space an operator builds. Industry estimates commonly put grey space at roughly 40-60% of a facility's total built area in enterprise and colocation designs, and the share tends to grow rather than shrink as buildings adopt liquid cooling, since CDUs, secondary loops and extra pumping skids add mechanical footprint without adding a single billable rack. Developers weigh grey-to-white space ratio alongside PUE when comparing site efficiency, since a leaner grey-space footprint at the same redundancy tier usually signals a more capital-efficient design.