Dual-pane windows: replace or repair?

Q: I've read your recent column about windows and have some related questions.

I have dual-pane windows whose cells have "leaked" and the inside surfaces are discolored. They are installed in traditional wood frames and are easy to remove. They have a metal/plastic composite spacer frame at the edge, sealed with some sort of black mastic. I have a number of cells that were replaced under warranty when water leaked inside and would like to see if I can rehab them.

If I can remove the spacer from one side, I could then clean the inside surfaces. Would isopropyl alcohol be a good cleaner, or would you advise something else?

Then, how would I ensure that I remove all possible water vapor before I reseal the edge? By moderately heating the cell? Or by injecting some type of gas? I would reseal with some type of mastic. Then I would put a layer of sealant all around the perimeter to try to plug the original leak.

Buying new replacement cells costs a bundle, and I have nothing to lose by trying to rehab these.

A: Our first reaction is to bite the bullet and buy new replacement Insulate Glass Units (IGU). They are expensive, but repairs can fail. Last winter, Kevin's daughter, Katie, busted the inside of a double-glazed window in their family room. Kevin thought about doing the repair, but it was in the middle of an Idaho winter and wife Heidi wouldn't stand for the delay.

The 3-by-3-foot IGU cost Kevin $130 and he did the installation himself. Unlike Kevin, you've got the time to tackle this job. You've also got the inclination. We say go for it.

You've got nothing to lose save perhaps a piece of glass you might break during the repair attempt. We wouldn't try to remove the spacer from one side and clean the two pieces of glass through the 1/2-inch slot. That's an impossible task, in our view. Rather we suggest that you remove one pane of glass entirely from the IGU, cleaning both interiors and resealing the IGU sandwich. ...CONTINUED

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