This project involves the rehabilitation of the existing building and the design of the extension of the Central Headquarters offices of Retena (Telecommunication Networks of Navarra). The absolute urgency of the construction work was decisive and in order to suply this issue doble shifts were employed, but there were no modifications in the architectural and construction quality of the solution provided. Building has passive solar control elements and a ventilated façade to provide a high level of energy efficiency. In addition, low emissivity glass electromagnetic deposition are used.