Foggy or Cloudy Window: What's Actually Going On
Fog that shows up between the panes of a window and won't wipe away, no matter which side you clean, means the seal on that insulated glass unit has failed. Humid air got into the gap between the two panes, and once that happens, no amount of cleaning fixes it. The layer causing the haze is sealed inside glass you can't reach.
Foggy or Cloudy Window
Why the Fog Won't Wipe Off
A dual-pane insulated glass unit works because the gap between the two panes is sealed and usually filled with dry air or an inert gas. That seal is what keeps the window insulating well and keeps moisture out of the gap. South Florida's humidity is hard on that seal over years of heat cycling, and once it fails, humid outside air gets pulled into the gap and condenses on the inside surfaces where nobody can wipe it.
You can tell it's a seal failure and not just dirty glass because the haze appears between the panes specifically, often worse in the morning or after a temperature swing, and it doesn't respond to cleaning either side of the window.
Foggy or Cloudy Window
What a Failed Seal Actually Means for the Window
A failed seal is mostly a clarity and insulation problem rather than a structural one. The window usually still closes, locks, and keeps weather out. What it stops doing well is looking clear and holding its insulating value, since the trapped moisture and lost gas fill reduce how well the unit blocks heat transfer.
This is a specialized repair category, and it's worth checking directly with whoever you call about whether foggy insulated-glass-unit work is something they currently handle, since it's a narrower skill than a standard pane swap and not every glass company takes it on.
FAQ
Frequently Asked Questions
Can I just clean the fog off my foggy window?
No. If the haze is between the two panes of a dual-pane window, it's condensation trapped inside a sealed unit that you can't physically reach to clean. Cleaning both outer surfaces won't touch it.
Does a foggy window mean I have a leak?
Not usually in the sense of water coming into the house. It means the gas-tight seal between the two panes has broken down over time, letting humid air in from outside. It's a separate issue from a window leaking water around the frame.
Does a foggy window cost more to run on air conditioning?
A failed seal reduces the window's insulating performance somewhat, since the trapped moisture and lost gas fill both work against the unit's original design. How much that shows up on a specific utility bill depends on the size and number of affected windows and the rest of the home's insulation, so it's hard to state as a fixed number.
Get a Straight Answer on Your Foggy or Cloudy Window
Tell me what you're seeing and I can usually tell you over the phone whether it's a repair or a replacement before I ever get in the truck.