This is a new traditional residence of 2.000m² with swimming pool in Porto Heli, Argolida. The design phase was in the years 2009 to 2010 with key criteria the most modern and environmentally friendly technologies. Underfloor heating was installed throughout the building for heating purposes and underfloor cooling combined with dehumidification units for cooling purposes. In each case the energy needed for heating and cooling purposes is produced using 100% geothermal energy. The heating of the swimming pool and the domestic hot water production during the summer months (May to September) is ‘’free’’ through heat exchange (rejection) of the geothermal heat pumps running in cooling mode. In general all the latest technologies were used for the proper and most economical operation of all building services with respect to the environment. We believe that the above mentioned mansion is a standard concerning the mechanical and electrical design.