YFW 400 TU Thermally Broken Fixed Window for Insulating Glass Elegant Simplicity for Efficiency YFW 400 TU thermally broken fixed windows are fully tested in accordance with AAMA standards achieving an AW rating. This fixed window was designed and engineered to be elegant with a 1-13/16 " sightline and to be efficient with superior air and water performance. Thermal U-factors range from 0.34 to 0.56 with common Low E, and Air and Argon filled IGU's with aluminum spacers. Benefits of Performance The YFW 400 TU performance can be integrated into smaller storefront and window wall punched opening applications. This contributes to LEED designs by optimizing energy performance as well as day-lighting and views to the outdoor environment. Couple this with YFW 400 TU's simple installation and the YFW 400 TU becomes the choice product for your next sustainable design. Versatility The 4 " depth design of YFW 400 TU Fixed Window integrates easily with YSW 400 T Horizontal Sliding Window, YVS 400 TU and YVS 410 TU Hung Window Systems using the same stacking mullions. YFW 400 TU meets the many design challenges required in remodeling, retrofitting, and new construction.