Sealed units
Foggy Window & Seal Repair
Haze trapped between two panes. It will not clear, it cannot be cleaned, and it is not the same thing as the frost you get on the inside in January.
- What failed
- The sealed unit
- What stays
- Frame, sash and hardware
- Visits
- Measure, then fit
- Defogging
- Not offered
Rule these out first
Four things that are not a failed seal
This is the most misdiagnosed fault in Minnesota housing, and three of the four lookalikes need no glass work at all.
Not this
Condensation on the room side
Water or frost on the surface facing into the room is indoor humidity meeting cold glass. You can wipe it. It means your air is moist and your glass is cold, and it is a ventilation question.
Not this
Condensation on the outside surface
Seen on humid summer mornings when the air conditioning has chilled the pane below the outdoor dew point. It means the glass is working, and it is the opposite of a failure.
Not this
Moisture between a storm window and the sash
That is a storm window with blocked weep vents, not a failed unit. Clearing the vents usually resolves it, and it matters because that trapped water rots the sash behind.
Not this
A dirty or hazy coating
Low-emissivity coatings and old cleaning residue can look like haze in certain light. If it wipes, changes with the angle or sits on one surface, the unit is intact.
How it actually works
What a failed seal actually is
Four steps from a sealed assembly to the haze you are looking at.
Two panes, a spacer and a sealed cavity
The cavity, usually gas-filled, is what insulates. The perimeter seal bonds the assembly and keeps outside air out. Everything else about the window is irrelevant to this.
A desiccant absorbs the small amount of moisture sealed in
It is built into the spacer. For years it quietly handles whatever moisture is present, which is why a slowly failing unit shows nothing at all.
The seal fails and the desiccant saturates
Thermal cycling works the perimeter seal continuously. In Minnesota it works harder than almost anywhere, because the assembly moves across a hundred and thirty degrees of range every year.
Then it fogs, apparently overnight
You are seeing the end of a long process, not the start of one. Once the desiccant is spent, moisture condenses in the cavity and the haze arrives quickly, which is why people assume something sudden happened.
By temperature
When you will notice it
Fogging is visible at some temperatures and invisible at others, which is why people doubt themselves.
70°F
Barely visible
On a warm dry day a failed unit can look almost normal. This is when people decide they imagined it.
40°F
Haze at the edges
Cool mornings bring the moisture out of suspension and the perimeter of the unit clouds first.
0°F
Obvious and widespread
The cavity is cold enough that moisture condenses across the whole pane. This is when most people call us.
-20°F
Ice inside the unit
At extreme cold the trapped moisture freezes between the panes. It is unmistakable, and it is also doing the spacer no good at all.
On the visit
How we tell the four apart
The whole diagnosis is working out which surface the moisture is on.
Can you wipe it?
If it clears with a cloth, it is on a surface you can reach and the unit is intact. This one question resolves a large share of calls before we leave the drive.
Which side is it on?
Room side means indoor humidity. Outside means dew point on a cold pane. Between two layers means either a failed unit or a storm window with blocked vents.
Is there a storm window involved?
If so, the moisture may be in the gap rather than inside a sealed unit. Different problem, cheaper fix, and it gets confused constantly.
How many units are affected?
Elevations fail together because they age together under the same sun. Counting properly is what makes the job affordable, because doing a whole side at once costs far less per window.
Minnesota conditions
Why sealed units fail in Minnesota
The widest annual range in the country is the hardest possible duty for a perimeter seal.
A hundred and thirty degrees of annual movement
From summer highs to winter lows, the panes, the spacer and the seal expand and contract across an enormous span every year. That cycling is the mechanical cause of most failures, and it is why units here commonly fail well inside the life they were sold with.
Ice dams putting water into glazing rebates
Water backing up under shingles reaches window heads and glazing rebates. A rebate that stays wet shortens the life of whatever unit sits in it, which is why we check before fitting new glass.
A generation of replacement windows now failing
Minnesota had an enormous wave of vinyl replacement windows fitted from the eighties onward, and those sealed units are reaching the end of their lives. The frames are often fine and the glass is replaceable inside them.
Extreme cold makes diagnosis easier, oddly
At twenty below, a failed unit is unmistakable and so is a humidity problem. January is a miserable month to fit glass but an excellent one to work out what you actually have.
Questions
Fogging questions
Will a foggy window clear up on its own?
No. The seal has failed and the moisture is permanently inside the cavity. It looks better on warm dry days, which is why people second-guess it.
Is defogging a real repair?
It improves the view and nothing else. It does not restore the seal or the gas fill, so we do not offer it.
Do I have to replace the whole window?
No. Only the sealed glass unit. The frame, sash, trim and hardware all stay exactly where they are.
Is frost on the inside the same thing?
No, and this is the most important distinction on the page. Frost on the room side is indoor humidity. Only moisture trapped between two panes is a failed seal.
Several windows fogged at once.
Normal. Units on the same elevation age together, and doing them in one visit costs considerably less per window.
My replacement windows have fogged already.
Common in Minnesota. The unit is usually replaceable inside the frame — you do not need to replace the replacements.
Coverage
Foggy window and seal repair across Minnesota
A mobile service covering the whole state, metro to the Iron Range. Pick your town below, or call and we will come to you.
Foggy Window & Seal Repair Across Minnesota
Related
Other repairs we handle
Windows and doors are the whole business, so whatever has failed, it is on this list.
Next step
Work out what you actually have
Free estimates across Minnesota, and an honest answer about defogging.