You've cleaned the glass inside and out, and the fog is still there — because it's between the panes, where no cloth can reach. That's a failed insulated glass seal, one of the most common window problems in Minnesota, and our freeze-thaw cycles are a big reason why.
Here's what actually happened inside your window, and an honest rundown of the repair and replacement options.
Why window seals fail
A double-pane window is a sealed sandwich: two panes, a spacer, a desiccant to absorb moisture, and insulating gas in between. Every day, temperature swings make the glass expand and contract, flexing that seal — thousands of cycles a year in our climate. Eventually the seal develops a microscopic breach, the argon escapes, and humid air gets pumped in. The desiccant saturates, and moisture starts condensing on the inner glass surfaces.
Sun exposure accelerates it, which is why south- and west-facing windows often fail first. Cheap insulated glass units with inferior spacers fail years sooner than quality ones.
What a failed seal costs you
Beyond the ugly fog, a failed unit has lost its argon fill — a real hit to its insulating value. In winter, you'll notice the glass feels colder and interior condensation and frost form more easily. The window frame may be fine, but the glass unit is done, and it won't heal.
Can foggy windows be 'defogged'?
Defogging services drill tiny holes to clear the moisture and install one-way vents. It can improve appearance temporarily, but it cannot restore the argon fill or the original insulating value — the window still performs like a compromised unit. We generally don't recommend it as anything more than a cosmetic stopgap.
Glass replacement vs. whole window replacement
If the frame and hardware are in good shape and the window is otherwise modern, replacing just the insulated glass unit can be economical. But when the window is 20+ years old, builder-grade, or showing other problems — sticking sashes, drafts, frame wear — putting new glass in an old window is spending good money on a failing asset. At that point, replacement gives you new frames, new seals, modern low-E glass, and a fresh warranty.
If several windows in the house are fogging, take it as a signal: they were likely all built with the same glass at the same time, and more failures are coming.
Get an honest assessment
JMB Builders evaluates foggy and failed windows throughout the Twin Cities metro and gives you a straight answer: repair the glass, or replace the unit — with written pricing for whichever path fits. Call 763-204-2099 for a free assessment.
