What To Do If Your Double Pane Windows Lose Their Seals

R-valueWindows let light into your home, but also are a conduit for air. To make windows more effective at keeping warm and cold air where it is supposed to be, double and even triple pane windows are the standard for new installations. These windows are energy savers, but homeowners may notice that in time, the windows get foggy and may even trap dirt between the panes - a sign that the seal has broken. How much of a concern is this and what should you do about it?

How Double Pane Windows Work


Double or triple pane windows are multiple layers of glass with either dead air or a gas such as argon or krypton between the pieces of glass. While a single pane window has an R-value of about .85, a double pane window increases the value to 1.5 – 2.0: when filled with argon gas the rate jumps to 2.7 – 3.6. R values used for windows are the same measurement used in insulation where the expected values are much higher.

A double pane window doubles energy efficiency as measured by R values and U values. A good window should also have a low U-value which reflects its thermal conductivity and a high R-value that measures its resistance to heat conduction.

When the seal breaks from exposure to heating and cooling, any gas inside escapes and the window fogs up. At first, the glass appears to be covered with a light mist that sometimes dries up over time and then mineral deposits form on the window, making it look perpetually dirty. The same mineral deposits can eventually erode the glass.

Remedies For Broken Seals


In the case of seal failure, you have four courses of action:

  1. Replace the window, frame and all. The most effective solution, replacing the window and frame, makes poor environmental sense. Old windows are condemned to landfills, all for a relatively small difference in energy effectiveness. Considering the amount of energy used in making windows, this makes little sense.



  1. Call in a glazier to replace one of the panes of glass. Done on-site, this process will use the frame you have for much less than what a complete new window would cost you. You still waste one piece of perfectly good glass, but the environmental costs are less.



  1. Have the seal fixed. Some companies specialize in installing a valve and seal on your existing window to expel the condensation. This process cleans the dirty inside glass, allows moisture to vent to the outside, and preserves the window with no wasted glass.



  1. Ignore the problem. The difference between a sealed window and an unsealed one is not that great in terms of energy loss. (You can test this by placing your hand in front of a sealed window and then unsealed one. You will notice little difference.) The bigger concern aside from energy loss is the unattractive look of a foggy window and the potential for mineral deposits, causing a perpetually dirty looking window.


With any of these processes, short of replacing the whole window with a new sealed one, the gas between the panes is history. The solution you choose depends on your budget, your concern for the environment, and your tolerance for dirty windows.