A double-pane window is two pieces of glass held apart by a spacer and sealed around the edge into a single unit. The space between them is dry and sealed on purpose. When that edge seal fails, the space stops being sealed, and outdoor air with moisture in it moves in and out with every temperature swing. The haze you are looking at is that moisture condensing on two glass surfaces you have no way of reaching.
That is why cleaning proves the diagnosis instead of solving it. You wash the outside, you wash the inside, and the cloud is still sitting there, because it is on the inner surfaces, sealed inside glass. There is no access, no panel to open, and no product that fixes it from where you are standing. In-place repair is not a thing for a failed seal. Replacement is the only honest answer anyone can give you.
Early on it is intermittent, and you may think you imagined it. Fog appears on a cold morning or after a big temperature swing, then clears by afternoon. That is moisture cycling in and out through the failed seal as the unit heats and cools. It is easy to miss for a whole season and easy to dismiss entirely when it happens not to be there the moment someone comes to look at it.
Later it stops clearing. Then the moisture that keeps evaporating and condensing leaves mineral deposits behind on the inner glass surfaces: streaks, spots, and a permanent haze that no longer moves at all. At that stage even a perfect cleaning would not help, because the deposits are etched onto the glass rather than sitting on it. The view does not come back. That is usually when people stop debating and start replacing.
The procedure is to drill a small hole or two through the unit, flush and dry the interior, and install a vent. The moisture leaves and the view usually improves, sometimes dramatically. If your goal is to be able to see out of a window before you list a house, it can do exactly that, and it is honest work when it is described accurately to the person paying for it.
What it does not do is restore a sealed insulated unit. The unit is now vented to the outside by design, which is the opposite of the thing that made it an insulated glass unit in the first place. And if mineral etching has already started, drilling and drying does not remove it. Understand which of those two outcomes you are buying before you compare the price against replacement.
Here is the part that gets left out of a lot of sales conversations. A failed seal is a glass problem, and glass can often be replaced while your window stays in the wall. The insulated unit is measured, ordered, and swapped, or the entire sash is replaced when the unit cannot come out of it. Your frame, your trim, your paint, and your drywall are all left alone.
That is a far smaller project than whole-house replacement, and it is the right one when the frames are sound and the windows still operate. It becomes the wrong one when the frame is rotted, the hardware has failed, the windows will not open, or a large share of the house fogged at once and you were already planning to replace. A contractor who does both has no particular reason to steer you toward the bigger job.
Two different problems get called the same thing. Water on the room-side surface of the glass, the kind you can wipe with a towel, is condensation from the humidity inside your house meeting a cold surface. It is worst in bedrooms and bathrooms on cold mornings, and it is especially common with older aluminum frames, which conduct cold straight through and turn the entire frame into a cold surface.
That version is about the frame, the humidity, and the ventilation, not about a failed seal. Sometimes it is solved with a bath fan and a humidity setting. Sometimes it is telling you that aluminum frames have reached the end of their usefulness in a Utah winter. Moisture sealed between the panes is a different animal entirely: unreachable, unwipeable, and solved only by replacing the unit that holds it.
It performs worse than it did, because the sealed space it depended on is no longer sealed. What nobody can honestly tell you is how much worse for your specific window, and anyone quoting a figure is inventing it. The practical answer is that it is a degraded window, it looks bad from both sides, and it will not repair itself over time.
No. It is a comfort and appearance problem rather than a safety one, and you can take your time comparing options. The exceptions are broken or cracked glass, which is a safety issue, and glass in a location that requires a tempered or laminated unit. It is also worth handling before you list a house, because a buyer's inspector will note it.
You can do one. New glass in an older window sometimes looks slightly different beside its neighbors, particularly in coating tint at certain angles, and it is fair to ask about that before ordering. Most people find one clear window less distracting than one cloudy one. Doing the fogged units on a single elevation together helps them look intentional.
Takes a minute. Or call 801-644-9000 and skip the typing entirely.