Whereas the energy demand of individual computers decreases steadily, the growing use of digital equipment in society and industry leads to an increase in the power output of computing centres. The thermal loads generated during the operation of IT systems considerably exceed classical loads (such as lighting, outdoor air temperature, solar loads) and must be dissipated. As a rule, this is afforded by ventilation systems. The requirements to be met by, and the dimensions of, these ventilation systems are essentially determined by the thermal power output of the IT systems, structural conditions and environmental requirements. Against this background, this standard specifies the criteria for the planning, erection and operation of computing centres in such a way as to reduce the energy demand for the technical installations needed to condition the installation spaces and areas used for IT systems to the required minimum. Requirements are specified for unmanned machine rooms without permanent workstations only.