Understanding Window Glass Options

Most window manufacturers have several glass options or “glass packages” that homeowners can select from. These options have different features or benefits and will impact new and replacement window energy efficiency. Here are the most common window glass options offered my major manufacturers:

Low E and Argon
Low E, or Low emissivity glass, is used on the outside pane of a window unit. The Low E coating will reduce heat loss in the winter and reflect the heat of the sun in the summer. The coatings used will impact the U Factor or the SHGC factor of the window, and the overall efficiency of the unit.

Double Panes and Insulated Glass
Insulated glass windows are constructed by including two panes of glass in the manufacturing process. The air between these panes of glass provides insulation value, thereby reducing the flow of heat. In addition to decreasing the conductivity of heat, it blocks more sound and the window is less likely to have condensation build-up (or foggy glass).

Gas Filled
Some window manufacturers offer gas filled windows. The most common gases to use are argon or krypton, which are less conductive of air. This can be a more expensive upgrade than Low E and Argon or double pane glass option, but it will provide much better insulating benefits.

There are many other window glass options available, but these are the most common. Be sure to review the options being presented by your contractor. In addition to reviewing the benefits of the window, ask to see the Energy Ratings (U Factor, SHGC, Air Transmittance) to compare the hard numbers between your options.