The purpose of this research was to measure the solar heat gain coefficients (SHGCs) of seven different window glazing products in combination with nine different window attachment products. The National Fenestration Rating Council (NFRC) funded this research for the NFRC Window Attachment Subcommittee. NFRC recognizes that window attachment products need to be rated but also knows that it is a complicated task. This research produced valuable data and information for NFRC and the fenestration community but also identified potential problems related to rating products that include “high-performance” glazing products. The importance of rating window attachment products is well known due to the fact that virtually all windows in residential buildings and most commercial buildings include window attachment products. Since window attachment products often have a greater impact on solar control than the glazing products to which they are added, the rating of these products needs to be a high priority for NFRC and the fenestration community.