The research project ZenN aims to reduce energy use in existing buildings and neighbourhoods. The project strives to: demonstrate the feasibility of innovative low energy renovation processes for buildings at the neighbourhood scale; identify, optimise and disseminate the most promising management and funding methods to facilitate large-scale implementation; develop, improve and launch ambitious replication plans at several scales (local, regional etc.) The three main challenges in connection with the near-zero renovation of existing buildings faced by the ZenN project are: technical challenges, financial challenges and property structure challenges.