Elementary and secondary schools are an important segment of the U.S. commercial building stock, both in terms of energy consumption and indoor environmental quality. In 2008, K-12 schools spent over 8 billion dollars on utilities, and approximately 30% of schools reported unsatisfactory indoor environmental conditions related to indoor air quality. There is an opportunity to address both of these issues by focusing on HVAC design and operation. Optimizing this particular building system can result in significant cost savings, as well as improved environmental quality for students and teachers. This report explores the existing literature on four single-zone HVAC systems – unit ventilators, fan coils, heat pumps, and package DX rooftop units – and discusses their potential for increased energy efficiency, cost savings, and improved indoor environmental quality.