This extension of the headquarters of Velux France was to be dedi¬cated to the company’s customers and partners, with a trading space on the ground floor and offices on the first floor. In addition to the functional aspect, the challenge was to design a model building in terms of energy performance, comfort and level of architectural integration with the regional environment, whilst at the same time portraying the Velux values and expertise. In particular, the layout of internal spaces needed to be designed for optimum daylight conditions, in order to guarantee visual comfort even in the centre of the building. A system of natural ventilation, through openings in the roof and lower parts of the building, was required to avoid the need for an air conditioning system in the summer. The roof is the key element of the new building and crystallises the three main objectives of the owner: • The architectural style of the zinc Mansart roof is a contemporary interpretation of typical Parisian sloping roofs. • The roof is contributive to the overall energy performance of the building. Like a gigantic protective shell covering the whole of the building, it also includes integrated solar panels which produce energy. • Numerous openings in the roof provide natural overhead lighting and ventilation to create a comfortable internal environment, even in internal bathroom areas, which benefit from conducted natural light. The energy performance achieved is all the more impressive because 33% of the surface is glazed.