Please proof this new article about double-paned windows. John McKenna mentioned.

[Brian A. MacNeish]

Originally Posted by John Snell

This is not exactly the case! Windows can, of course, lose their seal and you will then find moisture between the panes.

For argon filled window units, however, the issue is actually the result of pressure equalization between the high concentration in the window and the lower concentration in the atmosphere: they want to equalize and will if at all possible. Over time, argon escapes, even through a "normal " seal or window and the panes collapse; if the window is smaller than about 20"x20" it will often implode! Larger windows simply flex but will, ultimately, end up touching each other. You can see this with IR long before you can see the condensation (which occurs on the exterior of the panes). I'll attach in next posting.

My partner, Rob Spring, PE, and I authored a paper, A Unique Thermal Problem Found in Certain Double-Glazed Windows, a number of years ago on this. Along with many others, it is available as a free download (we only ask for your contact information) at our website:
http://www.thesnellgroup.com/WhitePapers.aspx.

This is a great find, especially before they go out of warranty!!!

Thermally yours,

John Snell
ASNT NDT Thermal/Infrared Level III #48166
Snell Infrared
800-636-9820
802-229-9820
http://www.thesnellgroup.com
http://www.IRTalk.com
http://www.learnnewsolutions.com/

Wouldn't this be the result of "partial pressures" equalization? Simple pressure equalization between the interior of the sealed panes and the atmosphere would not cause the glass to go concave and collapse towards each other.

[Brandon Clark]

I've always thought it was because the gas molecules that escape from the thermal seal are smaller than air molecules, so when the gas escapes the air can't take it's place causing the windows to pull together?