There are a number of ways to scientifically measure the energy-efficiency of windows. Long Windows are one of the most energy-efficient windows you can purchase, by any of these measures.
A key factor of energy-efficiency is R-vlaue, which measures the thermal insulation capability of a window. The higher the R-value, the better the window insulates to keep your home cool in the summer and warm in the winter.
Long windows have industry-leading R-values of 5.6 – 7.1. These are significantly higher than the R-values for typical single or double-pane windows.
Another factor in energy-efficiency is the U-Factor, which measures how well the product traps heat inside your home. In this case, the lower the value the more energy-efficient your window is. Long Windows have an industry-leading U-Factor of .14.
Yet another factor in energy-efficiency is the Solar Heat Gain Coefficient (SHGC), which measures how well the window blocks solar heat from coming inside the house. Again, the lower the value the more energy-efficient your window is.
Long Windows have an industry-leading SHGC of .24
A final factor in energy-efficiency is the transmission of UV light. Long Windows utilize Heat Mirror Technology, recognized in Popular Science magazine as one of the top 100 Inventions of the Millennium.
Long Windows with Heat Mirror Technology only allow .41 percent of damaging UV rays into your home. Other windows on the market today allow roughly 50% of damaging UV rays into your home.