Rau wins against strong competition with a CO2-neutral and energy positive design which, in terms of layout and sustainability, outperforms the requested standard. An interenational competitive tender for an office complex with social housing and retail in Lyon.Lyon, the Carré de Soie: where once the silk industry was located, there will be a model neighbourhood situated between the city centre and the airport. Accreted housing will be demolished to make way for a sustainable urban concept.Lyon’s great ambitions for sustainable technologies and low energy use must become a reality here. This first location-defining office complex with a shopping centre, a car park and 92 social housing apartments will set the standard for the whole city district, acting as a central hub. At the end of the metro line to the centre, immediately adjacent to a Park & Ride facility and on the tram route to the airport.The design involves various aspects. Sustainable use of materials, such as walls of recycled glass and recycled glass-reinforced concrete. Low energy use (class A EPBD), using only infinite energy sources and self-generated energy. And, in order to get as close as possible to our self-imposed additional objective: an entirely self-supporting and – autonomous – CO2-neutral design.Large golden fields full of sunflowers cover the south of France: their leaves feed the animals, their petals are used to give a golden colour to textiles and their seeds produce food and oil. And all this comes from the light to which the flowers invariably turn. The roofs are oriented towards the sun. Covered with photo-voltaic cells that gather sunlight and energy to be shared among all the residents.In terms of services, this will also be a sustainable complex. In the office building on the tram line and above the two layers of underground parking, in addition to a supermarket, there will be an organic restaurant and an organic food shop, which will also serve travellers. A ‘green’ bank will also have its office here. The sheltered apartment complexes are located around pretty courtyard gardens with the residents’ cars parked underneath.Through careful positioning in the location and relative to the sun, the best possible use is made of what is already there. This allows for optimum lighting and heat from the sun, and allows the residents to enjoy unimpeded views. Receding stepped walls provide their own shade. Light-coloured walls reflect the daylight into the neighbouring apartments. The local cool northerly wind is used for natural ventilation and cooling.Synergy between urban design, architecture, landscaping and building services: space allocation, walls, the ground level and the roofs are designed with a view to their urban location, architectural value and energy contribution. This integrated design was achieved by collaborating right from the start with two (French) partners specialising in building services and urban construction.