The Vaults Tower is a project for a residential tower in central London, characterized by a high degree of modularity to enhance off-site fabrication strategies. The vaults are designed as modular units that can be fabricated off-site and mounted on site minimizing the amount of formworks, reducing CO2 emissions and increasing the quality of finishes. The Vaults has been designed to frame the internal views from inside the flats and their volume work as thermal mass becoming a passive device for the energy efficiency of the tower. The terraced gardens work as shading devices reducing direct solar exposure of the flats during the summer, contributing to the energy efficiency of the tower. The terraces host plants creating a vertical green distribution, increasing the quality of the built environment and making this tower a landmark for a new way of conceiving sustainable residential developments suitable for off-site fabrication.