How should windows be labeled for energy efficiency?

The appropriate method for labeling windows for energy efficiency involves including the NFRC rating. The National Fenestration Rating Council (NFRC) provides standardized ratings for energy performance that are recognized and trusted in the industry. This label typically includes information on U-factor, solar heat gain coefficient, visible transmittance, and air leakage, which are crucial metrics for assessing how well a window performs in terms of energy efficiency.

By using the NFRC rating, consumers and building inspectors can make informed decisions based on comparative data, ensuring that they understand the potential energy savings associated with different window options. This not only helps in meeting energy codes and standards but also promotes greater energy conservation in buildings.

The other options do not provide a comprehensive measure of energy efficiency. For instance, labeling by brand name alone does not convey specific performance metrics. Energy rating stars can be useful but may not be universally applied or understood. Size classification provides information about dimensions rather than efficiency. Thus, the inclusion of the NFRC rating represents the best practice for energy efficiency labeling.