Northwest Energy Efficiency Alliance (NEEA) worked with Secondary Glazing System (SGS) manufacturers to measure the performance of their products using industry standard window testing procedures. This effort allowed building owners and design teams to effectively compare available product performance with consistent baseline conditions. The Ernest Orlando Lawrence Berkeley National Laboratory conducted this study to simulate and physically validate thermal and solar performance characteristics of seven window attachment Secondary Glazing Systems. This report introduces new methodology and software capabilities where industry standard practices do not exist, such as condensation resistance. It also evaluates the annual energy savings and condensation potential of all SGS systems in mid to large size commercial buildings.