Foundation piles are being increasingly equipped with heat exchangers to efficiently harvest shallow geothermal energy. For buildings in urban areas continuous flight auger (CFA) piles are common due to their speed, cost efficiency and low noise levels. To construct a thermo active CFA pile usually requires separate central installation of the heat exchanger. However the energy performance of this type of pile has not been investigated systematically, with most studies focused on rotary piles

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... ere the heat exchanger is attached to the reinforcing cage. In this work, insights are provided about the main influences on the energy efficiency of thermo active CFA piles, with a focus on the implications of using CFA construction techniques rather than rotary boring. An innovative 3D numerical model, able to capture the different aspects of transient heat transfer, is employed together with analytical methods to evaluate the transient and steady state behaviour of energy piles in a number of design situations. Attention is given to understanding the role of possible pipe to pipe interaction, which cannot be systematically investigated with standard methods. Finally, practical guidelines on the optimal choice of design parameters to maximise the energy efficiency of CFA piles, without altering the geotechnical arrangements, are provided.