Two words: efficiency and durability. Heat is transferred through windows in four ways: air leaks, radiation, convection and conduction. It’s not just the type of glass that influences heat transfer but the frames that secure the glass. The construction of Fortress Window’s vinyl frames minimizes the amount of air that can penetrate the frames. And because vinyl is a low-conductivity material, it reduces the amount of heat that can transfer through the frame making Fortress’s windows among the most energy-efficient in the world. That means lower energy costs throughout the year. In addition to saving money, Fortress’s windows will save you time.  Vinyl won’t crack, split, warp, peel or corrode; nor will it show scratches since the color is throughout.  This makes for a durable window that is totally maintenance-free.