Wisconsin foggy windows and what to do about them
Every fall we start getting the same call from New Richmond. Somebody walks past the living room window on a cold morning, sees it’s fogged up, and figures it’s just the weather. A few weeks later it’s still there. They wipe it. It doesn’t come off. They wipe the outside. Still there. That’s usually when they start searching for what to do about it, and that’s usually when they find out how much a new window costs.
So let’s start with the good news. If the fog is between the two panes of glass, the window frame is almost never the problem. The glass is. And the glass can be replaced on its own.
How to tell what you’ve got in about a minute
Wipe the inside of the glass with a dry rag.
If it comes off, that’s condensation from the air in your house. The glass is fine. It’s a humidity thing, and I’ll get to that further down.
If it doesn’t come off, go outside and wipe the other side. If it still doesn’t come off, the moisture is sealed inside the glass unit itself. That’s a failed seal.
What actually happened to your window
Most windows have two panes of glass with a metal or foam spacer running around the edge, sealed up at the factory. Inside that gap is dry air or argon, plus a little drying agent packed into the spacer to soak up whatever moisture snuck in during manufacturing.
That edge seal has a lifespan. Sun bakes it. Our winters freeze it. The glass expands in July and shrinks in January, year after year, and eventually the seal lets go. Once it does, humid air gets in, the drying agent fills up, and you get fog. Early on it comes and goes. Sunny afternoon, it’s there. Cold morning, it’s gone. Given enough time it leaves a white haze on the inside of the glass that never clears.
The other common cause is water. If the little drain slots at the bottom of the window get plugged with dirt or paint, water sits against the bottom edge of the glass and works on the seal from the outside. That’s the one to pay attention to, because the same water is sitting against the wood. Push on the sill. If it’s soft, you’ve got a bigger problem than fog.
What we do about it
We measure the old unit, order a new sealed unit to match, and swap it into your existing sash. Your frame stays. Your trim stays. Your paint, blinds, and screen stay. Most of the time it’s done in one visit once the glass comes in.
A few things I always ask about on the phone, so you can have the answers ready:
Does the window have grids between the panes? Those have to be built into the new unit.
Is it tempered? Look in a corner of the glass for a small etched stamp. Anything next to a door, near a tub, or big and close to the floor usually has to be safety glass by code, and the replacement does too.
Is there a name printed on the metal strip between the panes? That’s the spacer, and it often has the manufacturer and sometimes a date. It helps with matching, and it tells you whether the window might still be under warranty. Some manufacturers cover seal failure for a good number of years. Worth a look before you pay anyone.
The things that don’t work
People ask me about defogging, where somebody drills a couple of tiny holes in the glass, dries out the gap, and plugs it. I’ll be straight about it. It can clear the fog for a while. It does not put the seal back, and it does not put the argon back, so the window insulates a lot worse than it did from then on. If the haze has already etched into the glass, it won’t come out no matter what they flush it with. And if your window is under warranty, drilling it will end that.
Caulk is the other one. Caulking around the outside of the window is good for drafts and leaks. It does nothing for moisture that’s already sealed inside the glass. If someone tells you a bead of silicone will fix a foggy pane, they’re wrong.
When I’ll tell you to replace the whole window
I’m not going to put new glass in a window that’s falling apart, because you’d be calling me back in two years. If the sash is rotted, if it’s warped so badly it won’t lock, if the draft is coming around the frame and not through the glass, or if the window is built so the glass can’t come out without wrecking it, a full replacement makes more sense. I’ll tell you that on the first visit. I came out of residential construction before I got into glass, so I look at the whole window, not just the pane.
If the fog wipes off on the inside
This isn’t a glass problem. It’s a humidity problem, and it’s incredibly common around here in January.
Warm, wet air from showers, cooking, and breathing hits the coldest surface in the room, which is your window, and it condenses. It’s worst in bathrooms, in bedrooms with the door shut, and behind heavy curtains, because the curtain keeps warm air off the glass and the glass runs even colder.
The University of Minnesota Extension says moisture problems tend to start once indoor humidity gets above around 50 percent, and that you need to keep it lower than that during cold weather. Minnesota’s Center for Energy and Environment suggests that if you run a humidifier in winter, keep it in the 30 to 40 percent range and run it in short stretches.
Practical version: run the bath fan and leave it running for a while after the shower. Turn the furnace humidifier down when a cold snap comes. Crack the blinds at night. Buy a ten-dollar humidity gauge so you’re not guessing.
If you’re getting steady condensation with no humidifier running at all, that can mean the windows themselves are on the less efficient side, or the walls are under-insulated. Single-pane glass and units with failed seals run colder, so they’ll condense before the good windows do. Sometimes the window that fogs inside first is the one with a bad seal, and it’s telling you before the fog gets trapped.
Ready to get it looked at
We’re based in Amery and we cover New Richmond and everything within about an hour and a half of it, both sides of the river. Text or email a few photos: the whole window from inside, a close-up of the fog, the corners of the glass, and any printing on the spacer. Add a rough width and height of the visible glass. That’s usually enough for me to tell you what it is and what it’ll take.
Call or text (715) 410-8346, or see our glass repair page for the rest of what we do.