This work was commissioned by the GLA to evaluate the Energiesprong approach, which is unproven within the UK but may potentially offer a step-change in what is possible, promising to provide a state-of-the-art retrofit without many of the barriers associated with existing solutions. As part of a consortium lead by Frontier Economics, UCL Institute for Environmental Design and Engineering (UCL IEDE) was tasked with undertaking this assessment to provide the GLA with key decision-making support in the following areas: · The provision of a detailed assessment of the extent to which the Energiesprong model is transferable to London, through the development of a robust business case. · The identification of suitable ‘first wave’ London-based prototype properties (‘Energiesprong demonstrators’), working with the RE:NEW programme/Support Team. · The implementation of high-level assessment of the transferability of Energiesprong to three other international archetypal cities with similar buildings and retrofitting needs.