Windows today have argon gas filled in between the 2 or 3 layers of glass of the sealed insulated glass unit. The question arises quite often; how long will the argon stay in the windows? The short answer is there are to many variables to be specific, but an average of 20 years is a realistic answer. The argon actually leaks out of the glass, not through the seal, unless there is actually seal failure in the window. Glass has pores just like your skin. You can't see them usually, but they are there, and they expand and contract like most other things on Earth. The argon escapes in very small increments over time through the pores in the glass. The purpose of argon is to insulate. Argon is heavier than oxygen and acts as another barrier for radiant heat. So you could say that your windows will lose a small portion of the insulating value with which they started every year. Don't get too worried though. The argon is not nearly as effective as the Low E coatings which actually reflect the heat off the glass. If you live in the South, argon helps, but you would probably never notice a difference. It would also probably not affect your energy bill either. The winter is when argon would help the most because it insulates as opposed to reflecting heat. In extreme northern climates argon would be most effective because the weather stays cold much longer. Bottom line - don't sweat losing your argon gas from your windows. Concentrate on getting a better Low E coating on your glass, especailly in the South.
Jon Alan Wright
Jon Wright Roofing, Siding, and Windows
1915 Peters Rd., Suite 310
Irving, TX 75061