If you’ve ever shopped for windows in the U.S., you’ve probably noticed that most windows come with a National Fenestration Rating Council (NFRC) label listing energy performance numbers. Before the NFRC developed a standardized method of reporting U-factor and solar heat gain coefficient (SHGC) ratings for windows, manufacturers’ reporting methods were inconsistent. The establishment of the NFRC standard benefited window buyers by allowing for comparison shopping.
As long as windows have an NFRC label—most major U.S. brands do—window buyers can compare the performance specifications of windows from different manufacturers. (For more information on U-factor and solar heat gain coefficient, see “All About Glazing Options.”)
Europe is different
Unsurprisingly, European window manufacturers test their windows according to different standards than American manufacturers. That means buyers can’t directly compare window performance claims made by European manufacturers to the claims of U.S. manufacturers—unless the European manufacturer has gone to the trouble of getting NFRC labels for their windows. (Most haven’t, because getting the laboratory testing done to obtain NFRC certification is expensive.)
Several GBA articles and Q&A threads explain how European window manufacturers differ from U.S. window manufacturers when it comes to reporting U-factors and solar heat gain coefficient. (Many of these articles are listed in the “Related Articles” sidebar at left.) I think it’s time to collect the most important information from all of these articles and Q&A threads together in one spot.
The table below attempts to summarize some of the differences between the North American approach and the European approach when it comes to window design and window energy performance reporting.
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