Foggy Window Glass: Replace the Glass, Not the Window

If you can see a haze, streaks or droplets between the two panes of a window, and wiping both sides does nothing, the problem is inside the glass. That is a failed seal. It is a common problem in double-pane windows across Metro Detroit (Macomb, Oakland and Wayne Counties), and it usually does not mean buying a new window.

Most double-pane windows have a sealed glass unit: two panes of glass held apart by a spacer around the edge, with a seal that keeps outside air and moisture out of the space between them. In many cases that unit can be replaced on its own while the frame and sash stay where they are.

What causes fog between the panes

The seal around the edge of the glass works hard. Every day the glass warms up and cools down, and the air between the panes expands and contracts with it. Michigan makes this tougher, with strong summer sun and long stretches below freezing. Over the years the seal can let go. Once it does, damp outside air gets in, and the drying material inside the spacer fills up and stops doing its job.

After that, moisture condenses on the inside faces of the glass whenever the temperature swings. At first the fog may come and go. Later it can leave a permanent cloudy film or white residue that you cannot reach to clean.

Is it the seal, or just condensation?

Not every foggy window has a failed seal. Before you call anyone, check where the moisture is.

• Fog on the room side of the glass that wipes off is indoor humidity. Our post on why windows get condensation covers that.
• Fog on the outside of the glass on a cool morning is usually dew, and it clears as the day warms up.
• Fog, streaks or droplets between the panes that you cannot wipe off from either side point to a failed seal.

If you are not sure, take a photo of the window on a morning when the fog is at its worst. It helps whoever looks at it.

Why replacing just the glass often makes sense

When the seal fails, the frame, the sash and the hardware are often still in good shape. Throwing all of that away to fix the glass is not always necessary. Replacing the sealed glass unit keeps the window you already have and fixes the part that failed.

The new unit is made to the size of the opening in your sash. The old unit comes out, the new one is set in place and sealed, and the window goes back to working the way it did. Our fogged glass and broken seal replacement work is done this way whenever the rest of the window is sound.

Glass-only replacement may not be the right call when:

• The sash or frame has rot, cracks or warping, so new glass would go into a window that is already failing
• Many windows in the house are failing at once and the windows are near the end of their life
• The window is built so the glass cannot be removed without damaging the sash

In those cases a sash replacement or a new window may make more sense. Our post on whether to repair or replace goes through how to think about it.

What about defogging?

You may see services that drill small holes in the glass, dry out the space between the panes and seal the holes. This can make the glass look clearer for a while. It does not put back the original seal or the insulating gas many units are filled with, and the drying material inside the spacer stays saturated. It is widely treated as a short-term fix. Tempered glass, which is used in doors and in glass close to the floor, cannot be drilled at all.

Does a failed seal hurt anything?

At first a foggy unit is mostly a problem of looks and comfort. You lose a clear view, and the glass does not insulate as well as it did. Over time, though, moisture that sits in the window can stain the glass and leave the sash damp, so it is worth dealing with rather than living with for years.

What affects the cost

We do not quote prices without seeing the window, because every job is a little different. The things that change the price of glass replacement include:

• The size of the glass
• Whether the glass has to be tempered, as it does in doors and glass near the floor
• Coatings or tint on the glass
• Grids between the panes
• How the glass is held in the sash, and how easy the window is to reach
• How many windows are being done at the same time

The fastest way to get a real number is a free quote. We come out within 24 to 48 hours, measure, and tell you whether glass replacement makes sense for your window. New glass comes with our 10-year glass warranty.

Getting it looked at

If you have fog between the panes, send a photo through the free quote form or call us at (248) 250-8000. We will tell you plainly whether the glass can be replaced on its own or whether something else is going on with the window.