Improving the energy efficiency of buildings is an important element of the efforts to attain the German government’s ambitious energy and climate targets. After all, roughly 35% of energy is consumed by buildings in Germany - for heating, hot water, ventilation, cooling and lighting. Insulating buildings helps to lower energy consumption, save heating costs, and reduce the use of finite fossil fuels. In many cases, a well-insulated building envelope is a precondition for an economically viable use of renewable energy. Overall, the heating transition in the buildings sector, which is needed for a comprehensive energy transition, can only succeed if the energy efficiency of the buildings is significantly improved.