Guide · Window Cleaning
We get this call every week: "the windows were just cleaned and a couple of them still look cloudy." Sometimes that haze isn't dirt at all — it's inside the glass, where no cloth can ever reach. Here's what's actually happening, what fixes it, and what doesn't. Spoiler: we can't sell you the fix, which is exactly why you can trust this guide.
Nearly every window made since the 1980s is a sealed unit — two (sometimes three) panes of glass bonded around the edges into a sandwich, with dry air or argon gas trapped between them. That gap is the insulation. A spacer bar around the perimeter holds the panes apart, filled with a desiccant that keeps the trapped air bone-dry, and a sealant locks the whole thing tight.
Windows breathe. Every sunny day warms the trapped air and pushes it against the seal; every cool night pulls it back. Over decades, that pumping fatigues the sealant until somewhere, it lets go. Now humid outdoor air cycles in and out of the gap — and when it hits a cool pane, the moisture condenses on the inside surfaces of the sandwich.
At first it's an occasional morning haze that burns off. Then a permanent fog. Eventually, water can pool in the bottom of the unit and leave mineral tracks etched down the glass. The seal has failed; the window is no longer insulating the way it did; and critically — the surfaces that are dirty are the two faces no one can touch.
Because the alternative is a window cleaner scrubbing a fogged pane, charging you, and letting you conclude the cleaning didn't work. We'd rather tell you plainly: no cleaning service can fix a failed seal — including ours. What a proper clean does do is make the situation honest: with every reachable surface spotless, it's instantly clear which panes have genuinely failed and which were just dirty. Our crews point out suspected seal failures when we're on the glass, so you're never guessing.
Replacing the sealed unit is the usual answer, and it's less drastic than it sounds: if your frames are sound, a glass shop can swap just the glass sandwich — a fraction of the cost of new windows. Full window replacement makes sense when frames are rotted or warped, or you're upgrading efficiency across the house anyway. Defogging services — drilling, flushing, and venting the unit — exist as a cheaper cosmetic option; results vary, and the insulating gas is gone either way. We don't do any of these, so take this as it's meant: a map, not a pitch.
Seal failure is mostly age — but it can be helped along. The big avoidable cause is pressure washing at the glass: a high-pressure jet aimed at a pane's edge can breach a seal in one pass, which is one more reason siding should be soft washed and glass cleaned with hand tools and low-pressure pure water. Beyond that: keep weep holes clear so frames drain, and keep dark paint off sealed-unit frames that weren't rated for it (heat stress ages seals faster).
No — condensation on the room-side surface in winter is a humidity issue (indoor moisture meeting cold glass), and on the outside on summer mornings it's actually a sign of a well-insulating window. Only fog between the panes means a failed seal.
Typically 15–25 years, less on hot south- and west-facing exposures where the daily temperature swings are biggest. It's normal for units to fail one at a time, not all at once.
Yes — we point them out as we go. It's your glass and your call; you just shouldn't have to discover it by wondering why one pane "didn't come clean."