Many manufacturers do not reinforce their windows. The small fraction of those who do, use steel, which conducts the cold.
All Lifescapes windows are reinforced using solid composite reinforcement in our lock and keeper rails. The K-value (Thermal Conductivity) of this composite reinforcement is 730 times better than aluminum and 191 times better than steel.
In cold climates, where heating bills are a major concern, choosing windows with lower U-Factors will reduce the amount of heat that escapes through a window from inside your house to the outside.
ESM glass system is dual pane that achieves the thermal performance of triple pane. At a dual pane price! Better than Energy Star standard for northern climates in the US. Comparison numbers based on double hung replacement windows manufactured with dual pane glass.