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Question DetailsAsked on 5/26/2013

looking for a company in Nashville TN that fixes broken window seals that cause double pane windows to fog, without replacing the glass

looking for a company that uses a process to remove the condensation and repair the Window seal using a valve, without having to replace the physical glass

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Years ago there were a few models of windows where they tried building them this way to allow for replacing the inert gas between the panes if it leaked out, but they found that the valves leaked, letting moist air into the window cavity ! Therefore, as far as I know, no one produces this type of window any more.

Your problem is a blown seal, but you do not know where it is broken, and the break has to be sealed on the INSIDE of the glass frame (the positive side) not the outside of the glass frame (the negative side). Therefore, the entire unit has to be disassembled.

Some types of units can be disassembled, saving the glass to be cleaned and reused. Others are made such as to make it almsot impossible to salvage the glass. Except for very large panes, it is usually cheaper to just have a new double-pane unit fabricated and installed in your window frame, and only new units will be warranted.

The defogging companies you are talking about come to your house, drill a couple of vent holes in your outer window pane, flush the void with air and a dessicant vapor (usually alcohol) to remove the excess moisture causing the condensation, then plug one hole and install a so-called valve in the other. All they are doing is flushing out the excess moisture in the unit at that time - they are doing nothing about the cause of the original outside air infiltration, and are not replacing the noble gas (argon or other), so the thermal efficiency of the window unit will drop by typically 8-16%. In a triple-pane window they also perforate the inner membrane (Heat Mirror or whatever), thereby turning the triple pane window into a double pane - causing typically 15-25% loss of thermal efficiency, and greatly increasing the chance of interior pane fogging and inside icing.

The "defogging" might or might not remove the visual problems in the window - the condensation, when it dries, commonly leaves staining and streaking on the inside of the window, and sometimes rusty stains - just like washing your windows without a final squeegee pass. Also, because the process does nothing to seal the aource of the air leak, refogging is likely to reoccur within a year or less - sometimes in days, so it is almost certain to be an on-going expense, at typically several hundred dollars per treatment.

Also - this cannot be done on tempered glass, such as in most windows in or next to front doors, or in sliding glass doors, french doors, or floor-to-ceiling windows.

Cost appears to vary widely around the country - the typical quote seems to be keyed to a price about 1/3-1/2 the price of window replacement. However, this is an apples and oranges comparison, because while it may be 1/3-1/2 the cost of a full window replacement, replacement of just the sealed glass unit (which should last 15-30 years versus the indeterminate duration of defogging) is in the same price range. I have recently had sealed unit replacement done on a regular size casement window with failed triple pane seals (30% of new window cost), and a cracked 5 foot wide eyebrow window (50% of new window cost).

As I am sure you can guess from my commentary, I would recommend against having defogging done - while not a complete scam, I see it as a poor stopgap measure that does nothing to solve the cause of the problem. Have the sealed glass unit (glass including metal glass frame and seals) replaced.

Answered 7 years ago by LCD

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