Broward County Certificate of Competency 20-WD-21968-X
What causes foggy or cloudy glass between the panes of a slider?
A straight answer for Broward County homeowners, then what you can check yourself and when to call. Free estimate: (954) 906-1715.
Foggy or cloudy glass between the panes means the sealed edge of the insulated glass unit has failed. Humid air has leaked into the gap, and moisture now condenses inside where no cloth can reach it.
The nuance is where the fog sits. If you can wipe it off, it is ordinary condensation on a surface. If it stays put after you wipe both sides, the unit itself needs attention, and in most cases the glass unit can be replaced without replacing the whole door, as long as the frame is sound.
Why the seal fails
An insulated glass unit is two panes held apart by a spacer and sealed around the perimeter. The spacer contains a drying agent that absorbs the small amount of moisture trapped during manufacturing. Once the perimeter seal cracks or breaks down, outside air enters, the drying agent fills up, and moisture shows as haze, droplets or mineral-like streaks.
Broward conditions are hard on that seal. Intense sun and heat make the glass and frame expand and contract every day, and year-round humidity gives the moisture plenty to work with. Wind-driven rain pushing at the sill can keep the lower edge of the glass wet, and salt air near the coast adds to the wear. A slider is a very large piece of glass, so it flexes more than a small window, and that movement works on the seal over time.
Impact-rated glass is built differently, with a laminated layer designed to hold together when struck. Cloudiness near the edges of a laminated unit can be a sign of moisture reaching the edge as well, so it is worth having looked at rather than assuming it is cosmetic.
What you can check yourself
Wipe both sides
Clean the inside and outside surfaces. If the haze is still there, it is between the panes and the seal has failed.
Watch it through the day
Fog that comes and goes with temperature and sun may be a partly failed seal. Fog on the outer surface that clears by midmorning is usually just surface condensation.
Look for staining or a water line
Streaks, a haze concentrated at the bottom edge, or visible droplets inside the glass point to a seal that has been leaking for a while.
Check the sill and frame
Look for water staining, soft spots or corrosion at the bottom track and frame corners. This tells you whether the frame is sound enough to keep and just re-glaze.
Test how the door operates
Note whether it drags, jumps the track or fails to lock. Those problems alongside fogged glass can change the recommendation from a glass swap to a larger repair or replacement.
When to call a pro
A failed seal cannot be repaired from the outside with cleaning products, and we do not recommend drilling or injecting anything into the glass, especially on impact-rated or laminated units. Call us if the fog won't wipe off, if the glass is cracked or the laminate looks separated, or if the door also drags, leaks at the sill or won't lock securely.
Our window, door and shutter work is covered by Broward County Certificate of Competency 20-WD-21968-X. Replacing a glass unit in a sound frame is a repair-type job, but whether your city wants a permit can vary, so verify with your city's building department. A full impact-rated slider replacement does involve a permit, inspections and a permit closeout, and in the High-Velocity Hurricane Zone the product needs an approval for the HVHZ, usually a Miami-Dade NOA. Condo and HOA communities may also need board approval first.
Sliding Glass Doors work is done under Broward County Certificate of Competency 20-WD-21968-X (windows, doors, shutters & garage doors).
What a pro will do
- Confirm the fog is a failed sealWe look at the glass, the frame and the sill to separate a failed unit from surface condensation or a leaking frame.
- Replace the glass unit in a sound frameIf the frame, track and hardware are in good shape, a new glass unit can restore a clear view without replacing the whole door.
- Repair rollers, track, locks and weatherstrippingWhile the door is apart, worn rollers, a gritty track, loose latches and tired weatherstripping can be fixed so it slides and locks properly.
- Recommend replacement when the frame is the problemIf the frame is corroded, leaking or badly out of square, we explain the option of an impact-rated slider approved for the HVHZ, with permit and inspections handled.
Related questions
- Is foggy glass in my slider a safety problem?
- The fog itself is mainly a sign that the seal has aged out, and it is more a clarity and efficiency issue than an immediate hazard. Still, ask for a look at the frame and the opening's storm protection while someone is there, since a slider is the largest glass opening in many homes.
- Does a fogged unit mean I should replace the whole door?
- Not necessarily. If the frame is sound and the door operates and locks well, replacing only the glass unit is often reasonable. If the door is also corroded, leaking or hard to operate, replacing it with an approved impact-rated slider may make more sense. We can walk through both options in a free estimate.
- Will a new glass unit count as opening protection?
- Only if the new glass and door assembly is impact-rated and approved for the HVHZ. Opening protection is one category of wind-mitigation form OIR-B1-1802, completed by a licensed inspector. Florida law (s. 627.0629) requires insurers to offer discounts for wind-loss-mitigation features, but we can't promise any credit. You can try the free Wind Mitigation Credit Checker on this site.
- Do I need a permit to replace the glass in a slider?
- Repairs usually don't need one, but replacing a door with a new impact-rated slider does. Because requirements differ between cities and between a glass swap and a door replacement, verify with your city's building department.
- Can I just live with the fogging?
- Many homeowners do for a while, and the haze is mostly cosmetic. But moisture inside the unit tends to worsen, and fogging can hint at wear elsewhere on the door. Call (954) 906-1715 for a free estimate and we can tell you which route fits.
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