: Lower is better. A lower number means the window is a better insulator and keeps more heat inside during winter and outside during summer. Eurocraft Energy Efficiency Features
: Their windows feature five insulating chambers that prevent thermal bridging—a process where heat flows through poor insulators. Eurocraft Windows U Rating
: Use of Kommerling uPVC extruded profiles, which are designed for high insulation and durability against streaking or chalking. : Lower is better