There are three ways to handle a failed seal, and the right one comes down to the condition of the frame around it.
The three ways to deal with it
New glass in your existing frame. A glass company measures the failed unit, orders a new sealed one built to those measurements, and installs it where the old glass sat. The trim and paint around the opening stay untouched, and once the unit arrives the swap is usually finished in one visit.
A whole new window. This is the answer when the frame has trouble of its own, like rot in the wood, a sash warped enough to bind, or an older frame letting air and water past the glass. New glass in a failing frame just leaves the frame problem waiting for you.
A defogging service. These companies drill the glass and clear the fog out, and it is a cosmetic fix. The insulating gas that used to fill the gap is gone for good, so the window looks better and insulates the same as it did fogged.
Before you pay anyone for any of these, check the manufacturer's seal warranty. Some run as long as 20 years, so if your windows are on the newer side, dig out the paperwork first. A unit still under warranty may be covered before you spend anything at all.
What the fog is, and how to be sure that's what you have
A double-pane window is two sheets of glass bonded to a spacer, with insulating gas sealed in the gap between them. The whole assembly is one factory-built piece, called a sealed unit, though some shops will call it an insulated glass unit. When the seal gives out, the gas escapes and damp air takes its place, and the moisture in that air condenses on the inner faces of the glass where no rag can reach.
That gives you a simple home test. Ordinary condensation, the kind that shows up on a cold morning, wipes away from one side or the other. Fog from a failed seal stays put no matter which side you wipe, because it lives inside the sealed gap. If the haze won't wipe off, the seal is gone.
A failed seal costs you a little comfort along with the view. That gas was doing part of the window's insulating work, and once it has escaped, the window gives up some of its ability to hold heat in, which you feel most through a damp Portland January. A new sealed unit brings that back along with the clear glass.
Meanwhile the window keeps opening, closing, and locking, which is exactly why this repair gets put off for months. One homeowner online described working from home next to a failed window and "thinking about it all day long because I'm looking right at it."
Why Portland sees so much of this
Damp winters make a failed seal show up earlier here and look worse than it would in a dry climate. Portland also has a lot of houses that got double-pane windows in the 1990s, and those seals are reaching the end of their working life right about now. So if one window in the house has fogged and another is starting to haze, that's a generation of seals aging on schedule, and each one can be handled the same way, with new glass in the frame it already lives in.
It helps to know what you'd be ordering. The new sealed unit is built to your window's measurements, and it carries over whatever the original glass had in it, like grids between the panes or a coating on the glass, so the repaired window matches its neighbors when it goes back in.
Getting a fix-or-replace answer without a sales visit
A photo usually settles it. Email a picture of the fogged window to info@clearworksglass.com, or call (503) 887-8329 and describe what you're seeing, and you'll get an answer on whether a new sealed unit will fix it or the frame needs attention too. Estimates are free and come in writing, so the decision stays in your hands from the first call.
Clear Works Glass is based in SE Portland. Monday to Friday 7 to 5, Saturday 8 to 2, emergency line 24/7. Oregon CCB #261682, bonded and insured.