Rehabilitation of the Diagonal Vertical Tower

Originally designed in 1969 by architects Santiago Balcells and Francisco Mitjans, Torre Diagonal Vertical is a landmark of modern architecture in Barcelona. Inspired by Gio Ponti’s Pirelli Tower in Milan, it became one of the city’s first high-rise buildings and a symbol of innovation with its distinctive geometry and pioneering curtain wall façade, strategically located at the intersection of Avinguda Diagonal and Carrer Balmes. The recent renovation—led by Hines—sought to preserve the building’s architectural essence while upgrading it to meet today’s standards of energy efficiency, comfort, and flexible workplace functionality. One of the project’s main challenges was restoring the iconic curtain wall without altering its visual identity. To achieve this, the original exterior profiles were preserved, while the single-glazed panes were replaced with high-performance double glazing of similar coloration. Photovoltaic glass was subtly integrated into the opaque façade sections, enabling energy production while maintaining the building’s historic appearance. This careful and sustainable approach led to a 37% reduction in carbon footprint compared to a completely new façade system, and a 60% decrease in overall energy demand. The photovoltaic panels now generate approximately 20% of the tower’s energy needs. Functionally, the building has been reimagined to accommodate a multitenant office program. The ground floor features three separate entrances: a central one providing access to Banco Sabadell’s offices (occupying the first three floors), and two lateral entrances leading to upper-floor tenants. These connect to a newly created skylobby on the third floor, which serves as a shared hub with a reception area, meeting rooms, open workspaces, and a courtyard garden preserving three original palm trees. This courtyard also includes one of the tallest vertical gardens in the city, enhancing the connection to nature. The interior layout was redesigned to maximize flexibility, natural light, and user comfort. Original materials such as marble, wood, metal latticework, and backlit surfaces were carefully restored, while modern touches promote openness and adaptability. Open-plan floors, increased ceiling heights, centralized mixed-gender restrooms, and exposed structural beams highlight the building’s character while improving functionality. Underutilized exterior spaces, including rooftops and terraces, were transformed into green, accessible areas for informal work and relaxation. These spaces contribute to a healthier, more engaging work environment and reinforce the biophilic design strategy. Technically, the façade was upgraded while preserving its original geometry. Enhancements included improved thermal and acoustic insulation, condensation control, structural reinforcements, and the removal of hazardous materials such as asbestos. The renovation complies with current building codes while minimizing construction impact and preserving the architectural language of the original design. Torre Diagonal Vertical exemplifies how a historic building can be thoughtfully transformed to meet contemporary needs. By combining heritage preservation with advanced technology, sustainability, and a human-centered approach, the project proves that architectural legacy and innovation can successfully coexist in the modern urban context.