Guillaume was trained as a public policy designer and worked as a civil servant for French local authorities for 15 years. Specialised in energy efficiency and residential retrofit, he took part in the implementation and scaling-up of programmes on energy poverty alleviation and the structuration of energy advice services to citizens. His work as a Technical Assistant in the Energy Team of C40, the worldwide network of Global Cities, allowed him to work with frontrunner cities from all continents. Working now for BEUC, the European Consumer Organisation, he mobilises his expertise to best benefit the end beneficiaries of public policies and programmes, the consumers who undertake retrofit works for their homes.