Energy recovery from data center spaces seems like an obvious automatic energy saver. Typically, all the energy supplied to the electronic equipment becomes waste heat, and an average data center rejects large amounts of this heat energy to the atmosphere via dry coolers, condensers or cooling towers. This study will examine the opportunities to save energy using air energy recovery techniques in heating, ventilating and air conditioning (HVAC) systems, weighing the cost, complexity, and operation of systems and equipment against the savings benefits. While the sensible energy recovery is the apparent benefit, results affecting the humidity ratio will also be considered. Several energy recovery options are studied to determine the possible savings in several HVAC systems, including: enthalpy wheel heat exchangers; plate heat exchangers; heat pipe exchangers; and the data center hot return air directly such as dual duct VAV. The energy recovery will be reviewed for use in tempering outside air by way of direct mixing as well as indirectly with heat exchangers.