Dear Angie: Can low-E/argon gas be put in a window when the seal is broken, instead of replacing the entire window? — P.T., Philadelphia
Dear P.T.: Let's start by clarifying the purpose of low-E and argon gas.
Low-E, or low-emissivity, coating is applied to window glass to help reflect heat. Adding argon gas between the panes of glass adds increased insulation to the window. Combined, they offer excellent energy efficiency for your home. A seal failure, though, will "oxidize" the low-E coating and argon gas, making the glass appear streaky or foggy.
Technically, yes, gas could be added to the window. However, it might not be the best solution. The process to add the low-E coating and argon gas is an involved process typically done at the factory.
However, some window repair companies have begun offering service at a customer's home to correct a seal failure. These companies typically remove the insulated glass from the sash — the section of the window that holds the glass — and then reseal the spacer perimeter to prevent it from additional fogging. This is still relatively new technology, so be sure you're going to get a guarantee.
Typically, older double-pane windows consist of two panes of glass held together with caulk. With the glass expanding and contracting due to the weather, the seal would often fail, creating moisture in the windows.
High-quality replacement windows now typically use a glazing bead spacer that helps hold the glass in place, but moves with the glass, which helps eliminate that issue. If a window is equipped with a glazing bead, it is possible to remove the glazing bead, remove the glass, and have it replaced or remade into a new sealed unit that is a low-E/argon combination.
If the window is not equipped with a glazing bead, it's likely the sash was constructed or assembled around the glass. If this is the case, it can be very difficult or altogether impossible to replace the glass.
While it might be possible to replace the glass with a low-E/argon-filled glass, you should consider if the repair is worth the investment. A better option might be replacing the entire window with a newer window that is airtight and already equipped with the low-E/argon glass combination.
If you're set against changing out the entire window, adding a new insulated pane of glass might be the most economical and practical way to go.