Foggy Windows in Winter? How to Tell Condensation From a Failed IGU

Every December the calls start: windows across Northwest Arkansas fog up, and homeowners want to know whether something is broken. The answer depends entirely on which side of the glass the moisture is on. One kind of fog is a humidity issue you can manage yourself. The other is a failed insulated glass unit that will never clear on its own. Here is how a glazier tells them apart, and what to do about each.

The Three Kinds of Window Fog

• Fog on the inside surface (you can wipe it with your hand): interior condensation. Warm, humid indoor air is hitting cold glass and dropping its moisture, the same physics as a cold drink sweating in July. This is a humidity problem, not a glass problem.
• Fog on the outside surface: exterior dew, common on high-performance low-E windows on cool mornings. Counterintuitively, this is a sign your glass is working well. It burns off by mid-morning.
• Fog between the panes (no amount of wiping touches it): a failed IGU. The sealed unit has lost its edge seal, moisture-laden air is cycling inside the cavity, and the desiccant that once absorbed it is saturated. This one needs a glazier.

Managing Interior Condensation

Arkansas winters push a lot of moisture indoors: cooking, long showers, humidifiers, a houseful of holiday guests. If your inside glass sweats, run bath and kitchen exhaust fans longer, crack the humidifier down below 40 percent, and open blinds during the day so air circulates against the glass. Persistent sweating on single-pane windows or old aluminum frames is really a thermal problem: the glass surface is simply too cold, and the durable fix is upgrading to an insulated unit with a low-E coating, which keeps the room-side glass surface warm enough that moisture never condenses.

What a Failed IGU Is Costing You

An insulated glass unit works because the sealed air or argon space slows heat transfer. Once the seal fails, that gas fill is gone, the U-factor of the window degrades, and the low-E coating inside the unit can begin to corrode, showing up as a permanent milky haze or rainbow-colored staining. You will feel it as a colder room and see it as a window that always looks dirty. Left long enough, mineral deposits etch the inner glass surfaces permanently.

The Fix Is Smaller Than You Think

Here is the good news we deliver on almost every fogged-glass call: you do not need new windows. We measure the failed unit, fabricate or order a matching replacement IGU, and install it in your existing frame, sash, and glazing channel. Frames, trim, and siding stay untouched, and the cost is typically a small fraction of window replacement. It is also an upgrade opportunity: replacements can be built with better low-E coatings and argon fill than the original builder-grade unit, improving both U-factor and summer solar heat gain performance.

Count Your Foggy Panes This Week

Cold, clear December mornings make failed units easy to spot, because the temperature difference maximizes the fog. Walk the house early, note every pane that stays hazy after a wipe, and send us the count. Request a free estimate, or give our Bentonville shop a call, and we will get clear glass back in before the January cold really sets in.