An increasingly important factor in the construction of data centres is the use of modular building blocks as opposed to bespoke facilities. This modular approach is becoming popular due to lower costs, shorter building times, and flexibility of design. However, as this flexibility gives a broad spectrum of configurations, there is significant scope for analysing the energy efficiency aspects of the modular approach. In order to have a deep insight into the total energy consumption of both large data centres and smaller facilities more research is needed to determine how intrinsically efficient the approach is.Thus the main goal of CoolEmAll is to provide advanced planning and optimisation tools for modular data centre environments. Once developed, these tools should help to minimise the energy consumption, and consequently the CO2 emissions of the IT infrastructure with related facilities. This will be achieved by:(i) Design of diverse types of computing building blocks (ComputeBox Blueprints) precisely defined by energy efficiency metrics;(ii) Development of simulation, visualization and decision support toolkit (SVD Toolkit) that will enable analysis and optimisation of IT infrastructures built of these building blocks;Both activities will include three important aspects when considering the energy efficiency of modular data centres: cooling techniques, applications properties, and management policies.To achieve these goals CoolEmAll will follow the interdisciplinary approach using project partners' expertise and technologies in relevant areas. Validation of results will be done by both real-life and simulation studies. The former will be possible thanks to the small scale real prototype of ComputeBox with fine-grained monitoring. Simulation studies will allow analysing and optimising energy efficiency in specific scenarios and designing ComputeBox Blueprints leading to potential energy savings of 10-50% depending on a specific case.