300 Million-Year-Old Limestone Houses Ultra Efficient Data Center 22 Stories Underground
This data center doesn't rely on a raised floor like most data centers at surface level. Instead, they use the cool from the limestone walls - which can absorb 1.5 BTUs per square foot - and vents attached to ceiling ducts. The server racks trap electrical heat and force it up through ceiling tiles, where the limestone absorbs the heat naturally. In addition, the HVAC system uses the ancient environmental features of the caves, pulling water from a several hundred-acre underground lake for cooling.
Computerworld states, "By setting the room's return air temperature to 75 degrees, Iron Mountain cut energy consumption for cooling by between 10% and 15% compared with the company's traditional data centers."