My project, located in Plaza de España, Madrid, is the result of thermodynamic analyses. The main idea is to have a central radiant wall made out of concrete which works together with large concrete volumes, that have thermal mass, and smaller modular units of 5x5m, that are made of wood and provide insulation. The radiant wall works thanks to the geothermal system and to the concrete slabs of the larger volumes which get heated up by solar radiation. The concrete part and the wooden one work together in heating up and cooling down each other by convection and conduction. The northern facade is more porous whereas the southern one is more compact, as a consequence of the favorable winds. The concrete volumes are risen 33m from ground level as to be higher than the surrounding buildings in order to receive more solar radiation during the winter. They are arranged in a way to form large, self shaded terraces (in summer) which are public spaces with vegetation and reflecting pools of water that help cooling down the air and rise the humidity. These spaces during the winter can be closed and work as greenhouses which help the concrete large units to heat up and these therefore heat up the wooden insulated units.