The building goes up in the neighborhood of Bolueta, by the Nervión River, on a plot previously occupied by several constructions related to the steel industry. In 2005 a project was launched to regenerate the area with the construction of seven large residential blocks including 1.100 apartments, recovering a space that showed signs of decay from the impact of industrial activity. In 2012, the studio VArquitectos won the competition for the construction of the first two buildings, of 171 and 190 dwellings respectively. The property asked for an improvement of the project’s energy efficiency, so the apartments were adapted to the Passivhaus standard.

To meet the standard, each and every one of the design elements were studied, and the building envelope in particular. The facade, covered with aluminum composite panels, consists of three types of parts: one flat, and another two with opposite slopes (upwards and downwards). The final design offers a broken and haphazard image that seeks reducing the visual impact of such large volumes. In terms of composition, this chaos is apparently supported by vertical bands where the different parts are connected with clear criteria: the windowless bands follow the same rhythm (flat, down, up); those with openings offer two different sequences; and finally, an effort is made to keep contiguous surfaces with the same inclination from coinciding. In this way, the repetitive pattern of the windows is melded into a fragmented, rhythmic, and bright facade whose colors evoke the materials that have forged the character of this area in Bilbao: steel and coal.

To achieve a zero net energy consumption, aside from increasing the insulation’s thickness, using building solutions to eliminate thermal bridges (or reduce them as much as possible), and installing high-performance window frames and glazing, all the apartments must be airtight. By preventing draughts it is possible to guarantee controlled and high-quality air renewal, as well as the possibility of recovering up to 90% of the heat of the interior stale air. In total, these improvements entailed a 3% increase of the construction budget, but the initial efficiency was inceased by 80%. The total cost in any case is within the usual price per square meter for subsidized housing in the Basque Country. The first tower, completed in 2018, became at its 88 meters in height the world’s tallest building with a Passivhaus certificate.