: Use of Kommerling uPVC extruded profiles, which are designed for high insulation and durability against streaking or chalking.

Your target U-rating should depend on your local weather patterns: Guide to Energy-Efficient Windows

The (or U-rating) for Eurocraft windows typically indicates high energy efficiency due to their multi-chambered uPVC construction and insulated glass. While specific U-ratings vary by model and glass configuration, high-performance windows generally aim for a U-factor of 0.30 or lower . Quick Guide to Window U-Ratings