Never heard such a thing as a seal failure does not effect the glass itself only the moisture has entered the air space.

The glass does appear concave in the sash. I can't answer the frost question because I never saw it myself. The girl at Andersen did refer to it as collapsed glass. You say that collapsed glass doesn't involve seal failure. Then what causes it and how can it be repaired? Also does the collapsed glass reduce thermal efficiency? I have Andersen casement windows at my house as well and I noticed distortion in some of my sashes too, but I can't say I ever had any frost problems.

It is a seal failure but not like we commonly think of. The seal on these Andersen windows in question allowed the argon to diffuse through it while not allowing air behind it to replace the lost volume. The escaped gas without being replaced created a negative pressure inside the IGU and would actually allow the glass to touch (if large enough) in the center. This creates a major weak point in the thermal part of the window.

The prescriptive fix is to drill the space on the window and release the negative pressure and therefore allowing the window IGU to return to proper spacing and close to normal insulation value.

That's very interesting and I suppose this happens due to the smaller molecular size of the Argon gas as opposed to just plain old air. you would think that the negative pressure would keep the gas from leaking out. It seems as though these windows defy the laws of physics something like a black hole! Drilling a hole to relieve the vacuum would require dissembling the sash, no doubt. That to me sounds like major undertaking due to the welded vinyl corners. I would probably not be able to get it back together very good either. Also why is it only on some rather than all the sashes?

How does one respond directly to a comment on this forum? I looked everywhere for a reply icon and can't find anything.

If the glass is physically touching in the center, as WoW noted, then replacing the glass is the only option, however if the glass isn't physically touching then the IG can be repaired, again as WoW noted.

https://www.youtube.com/watch?v=wq_LJnoi33w

Here is a youtube link to a method of drilling into the IG unit. It isn't really difficult, but it is necessary to be precise.

And you are correct that the idea of negative pressure between the lites of an IG does seem counter-intuitive at the very least, but it's real.

oberon476 Thanks so much for the link. That's incredible! You may have saved me some big bucks. Next time you're in town the beer's on me!

I found this on the internet......One rare yet shocking consequence of argon leakage is the sudden implosion of the window.Due to molecular differences between argon and the principal components of air, nitrogen and oxygen, argon under pressure to escape a window unit may exit the seal faster than it can be replaced with air. Under this circumstance, the glass will bend inward to accommodate the gradual reduction in pressure within the window. If conditions are right, according to USGlass Magazine, “units have been reported to shatter with a bang, sometimes described as loud as a gunshot. While the broken glass usually stays within the unit, on at least one occasion, glass has shattered with enough force to send glass shards flying outward.” Elevation differences between the location where the IGU was first pressurized and its installation location may also account for the negative pressure. This phenomenon is quite rare, however, especially in newer windows with superior seals.