Summary  In this conversation, Nancy Kohout, a licensed mechanical engineer and senior principal at Smith Group, discusses the critical importance of decarbonization and sustainability in the building industry. She emphasizes the need for strategic long-term planning in retrofitting existing buildings, addressing air leakage, and navigating electrical capacity challenges. Nancy also highlights the role of new technologies, such as geothermal systems, in achieving decarbonization goals. The discussion further explores the significance of collaboration, mentorship, and leadership in fostering a diverse and inclusive engineering community, ultimately envisioning a future where heat is treated as a commodity and sustainability is integrated into all aspects of building design.    Key Takeaways  Decarbonization requires a systematic approach and long-term planning.  Benchmarking building performance is essential for effective retrofitting.  Air leakage can significantly impact heating loads and energy efficiency.  Understanding electrical capacity is crucial for implementing new technologies.  Geothermal technology offers significant potential for decarbonization.  Collaboration and knowledge sharing are vital for industry progress.  Mentorship is important for fostering diversity in engineering.  The industry must adapt to new technologies and changing regulations.  Sustainability should be viewed as a business opportunity, not just an obligation.  Future strategies should focus on treating heat as a commodity.