Urban areas, which are expected to host more than two--thirds of the world's population by 2050, provide unique opportunities for the implementation of the radical policies needed to meet the Paris Climate objectives. Pioneer municipalities in Europe are leading the transformation needed to achieve zero energy and/or zero carbon communities by integrating policies across different sectors (buildings, transport, waste, water and energy supply). Critical factors identified through the analysis of existing initiatives include first, having clearly defined long--term targets, community boundaries and values, second, linking targets to community priorities such as economic development and urban renewal, and third, transposing long--term goals into milestones and short--term objectives to avoid discouraging the community. Challenges identified include first, capacity building, second, citizen participation and third, adequate project documentation as well as monitoring of the achievements. This paper focuses on the zero energy target at a com--munity level, but some of the projects analysed aim at zero carbon and not necessarily at zero energy. The discussion on the differences between the zero energy and the zero carbon concepts is out of the scope of this paper. However,
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