The book "Sustainable Energy in the Built Environment - Steps Towards nZEB" addresses the key challenges involved in implementing the concept of Nearly Zero Energy Buildings (nZEB). It begins with an analysis of energy requirements and the available renewable energy sources in construction, considering both the limitations and opportunities for developing sustainable, efficient, and cost-effective solutions. The aesthetic and architectural acceptance is also discussed. In the following chapters, advanced solutions for meeting energy needs through various renewable energy sources are presented, with a focus on the efficiency of conversion at the component and system levels. Another chapter is dedicated to innovative approaches for water reuse and waste recycling as secondary raw materials. Finally, the necessity for new strategies and implementation tools for education and training within the nZEB framework is discussed to promote sustainable communities.