In this paper is presented methodological approach to the energy efficiency optimization of high density data centre, in a synergy with relevant performance analysis of corresponding case study. Related case study goal-to optimize energy efficiency to the level characterized by the power usage effectiveness nearly equal 1 (PUE approximate to 1), has been successfully realized, tracing an energy efficiency optimization road to a hyper energy efficient data centre of the superb IT and energy performance. In addition to the corresponding energy densities, and energy efficient removal of extremely high heat dissipation, to reach superb IT performance very special focus is to be devoted to finally controlling indoor air temperature and humidity conditions. It has been shown that, by an integrated approach to the optimization of building construction, data centre's intrinsic IT systems and equipment selection is to be done also with the reference to its specific energy efficiency and the most recent breakthroughs in IT infrastructure fields, as well as in data centre's high performance air-conditioning and infrastructure's high precision cooling. Finally, data centre greening, implementing renewable energy sources has been analysed. (C) 2014 Elsevier B.V. All rights reserved.