By the year 2025 Rotterdam aims to have halved its CO 2 emissions; an ambitious plan that will require a revolutionary approach to urban areas. One proactive response to this challenge is an exploratory study of the Hart van Zuid area. An interdisciplinary team has investigated how to tackle CO 2-issues in a structured way. This has resulted in the Rotterdam Energy Approach and Planning (REAP) methodology. REAP supports initial demand for energy, propagates the use of waste streams and advocates use of renewable energy sources to satisfy the remaining demand. REAP can be applied at all levels: individual buildings, clusters of buildings and even whole neighbourhoods. Applying REAP to the Hart van Zuid has shown that this existing area can become CO 2 neutral. Best of all: REAP can be applied everywhere.