Andersen glass failure due to negative pressure
Oberon: This question is for you since you are very knowledgeable about windows. I just read your thesis on condensation, and all I can say is - "Wow!"
Getting back to my problem. We installed Andersen 400 series High Performance windows in 1989 and maybe 7-8 yrs later I noticed an oval pattern of condensation on the inside of the glass (not between the panes). I thought it was strange but since it wasn't between the glass I thought everything was okay. Fast forward to a few months ago and I discovered a diffent window had, indeed, failed (cloudiness and smears between the panes). I went to Andersen's website to notify them and to my surprise they mention the problem of the oval condensation in the center of the window!
I rec'd an email from their rep who said the oval condensation was probably an indication of negative pressure and I could tell by measuring the space between the glass at the edge and at the center of the window. (Do this by placing something on the outside [husband's finger] and your finger on the inside.) To my amazement more than half of our windows and three 36" French doors had almost no space between the glass in the center (3.5 mm on the edge and 14 mm in the center). His email also said that it could be repaired (and did not need to be replaced). Andersen then sent out a local contractor to assess the failure. To my delight this contractor said he would have the glass replaced; that if the difference was more than 4 mm Andersen will replace the glass.
Oberon, you probably know how the glass is repaired but for those of you reading this that don't know, I will tell you what I was told: They drill a small hole in the frame releasing the pressure and fill the space with air (not Argon gas as original), then plug the hole and in their words it's "still as good as the best windows on the market," stopping short of saying "as good as before the failure."
I hope that Andersen does indeed replace the glass, but on the chance that they won't, I want to know your opinion, re repair or replacement. The contractor was here on Jan 8th so I'm thinking it will be a while before I get any real confirmation from Andersen.
Sorry this is such a long message but I thought those of you with older Andersen windows would like to know my experience so far. I know they have made a lot of improvements since my windows were made in 1989, and I still think they make a good product.