The IEA EBC Annex 64 - LowEx Communities was a three year international research project which aims to demonstrate the potentials of low exergy thinking on a community level as energy and cost efficient solutions to achieve 100 % renewable and GHG emission-free energy systems. Central challenges are the identification of promising and efficient technical solutions for practical implementation. Aspects of future network management and business models for distribution and operation are as well essential for successful implementation and have been covered in the working phase. Aspects of transition management and policy will ensure the feasibility. The main objective of the annex is to demonstrate the potential of low exergy thinking on a community level as energy and cost efficient solutions. The intention is to reach these goals by providing and collecting suitable assessment methods (e.g. holistic balancing methods). Furthermore, guidelines, recommendations, best-practice examples and background material for designers and decision makers in the fields of building, energy production/supply and politics are provided. www.annex64.org.