Understanding Energy Codes and Standards for Windows

This technical report outlines the energy performance standards and codes applicable to windows in residential and light commercial buildings. It discusses the importance of windows in energy efficiency and human comfort, emphasizing the role of the International Energy Conservation Code (IECC) in establishing baseline performance levels based on climate zones. The report details various performance metrics such as U-factor, Solar Heat Gain Coefficient (SHGC), and air leakage rates, explaining how these factors influence energy conservation in building design. It also presents the National Fenestration Rating Council (NFRC) as a key organization providing objective ratings for window performance, while noting differences in testing standards between the U.S. and Europe. Furthermore, the report describes compliance options for energy codes, including prescriptive compliance and performance-based alternatives, and highlights enhanced performance standards like ENERGY STAR and LEED that aim for higher energy efficiency in window products.