This report employs a Smart Energy System approach to redesign Europe's energy infrastructure, emphasizing the expansion of district heating as a strategic move to eliminate gas-based heating in European buildings. It introduces a novel quantification of waste heat potentials and integrates it with analyses of future potential district heating market shares in Europe. Both in a REPowerEU 2030 and long-term decarbonization temporal perspective. Additionally, it provides a quantification of the investment required in district heating infrastructure to achieve substantial reductions in the EU's natural gas consumption. This report contributes to the ongoing the Heat Roadmap Europe project series.