We have totally refurbished Challenger, our own head office, twenty years after it first opened. The twin aims were to increase energy and environmental performance while improving the working conditions of the 3,200 people employed there. The project included the replacement of 88 % of the facade by a double-skin facade with very high thermal performance and the installation of more than 25,000 m² of photovoltaic solar panels. All of this makes Challenger one of the very first renovated positive-energy commercial buildings.