This collection of ten case studies addresses the unique challenges surrounding the improvement of energy consumption and thermal comfort in modern buildings built between 1931 and 1969 and offers valuable lessons for other structures facing similar issues. These buildings, international in scope and diverse in type, style, and size, range from the Shulman House, a small residence in Los Angeles, to the TD Bank Tower, a skyscraper complex in Toronto, and from the Calouste Gulbenkian Foundation, a cultural venue in Lisbon, to the Van Nelle Factory in Rotterdam, now an office building. Showing ingenuity and sensitivity, the case studies consider improvements to such systems as heating, cooling, lighting, ventilation, and controls. They provide examples that demonstrate best practices in conservation and show ways to reduce carbon footprints, minimize impacts to historic materials and features, and introduce renewable energy sources, in compliance with energy codes and green-building rating systems. The Conserving Modern Heritage series, launched in 2019, is written by architects, engineers, conservators, scholars, and allied professionals. The books in this series provide well-vetted cased studies that address the challenges of conserving twentieth century heritage.