Replacement Windows: Which Glass Should you Consider?

It's vital to choose the best kind of replacement window glass for your climate. The NFRC label on a window includes information about the glass and every contractor or window retailer uses this label to rate a window. This label will tell you how well your window would be, both energy efficient wise and how well it will hold up in the long run.

Double-paned (double-glazed) windows have two layered panes of glass. The air in the space between the panes serves as insulation. All single pane windows are a thing of the past now.

Triple-glazed windows have three layered panes and provide even better insulation.

Gas-filled windows are double- or triple-paned and have a gas like argon or krypton filling the space between the panes of glass; the gas provides better insulation than just a layer of air does, because the gas is heavier than air. The NFRC label will list what type of gas in used for that particular window.

Warm-edge spacers (sometimes called warm-edge technology) hold the panes of glass in a double- or triple-paned window apart. They are made of a material that reduces heat transfer and improves insulation. Foam is sometimes used as insulation as well.

Low-E (low-emissivity) glass is coated with a transparent metal film that reflects heat. Low-E coatings reflect radiant heat off the inside of the windows and back into the house to help keep it warm in the winter. Most low-E coatings also reflect some of the sun's heat off the outside of the windows, limiting how much of it enters the house.

High-performance glazing is glass that has several features designed to make it more energy efficient, such as two or three low-E gas-filled panes with warm-edge spacers.

Visible transmittance measures how much visible light comes through a window on a scale of 0 to 1.The higher the number, the more visible light you'll receive. You can find the (VT) on the NFRC label.

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