Common Window Problems: Foggy Glass, Sticking Sliders, Condensation and Leaks

Diagnose before replacing

Most window complaints have a specific cause, and several do not require replacement.

Fog or haze between the panes

This is insulating glass seal failure. Moisture has entered the sealed cavity and condenses on the inner surfaces, sometimes leaving a permanent mineral haze. The frame is usually fine.

• The insulating glass unit can often be replaced without replacing the window, if the sash and hardware are sound and the unit is still available.
• Seal failure is the most commonly covered item in manufacturer warranties — check before paying for glass.
• If many units across the house have failed and the windows are single-pane-era aluminum, whole-window replacement usually makes more sense.

Condensation on the interior glass surface

This is almost always indoor humidity meeting a cold surface, not a defect. It appears first on the least insulating surface in the room. Remedies are ventilation, bath and kitchen exhaust use, and reducing moisture sources. A window with a warm-edge spacer and better U-factor resists it, which is why it often disappears after replacement — but the underlying cause was humidity.

Water intrusion at the sill or adjacent wall after rain

This is almost never the glass. In stucco construction the usual causes are:

• Failed or missing flashing at the head and sill
• Stucco cracking at window corners channeling water behind the finish
• Failed sealant joints at the retrofit fin
• Weep holes blocked by paint, debris or caulk

Blocked weeps are worth checking first because the fix is free. Water staining at the sill, soft framing, or bubbling drywall below the window indicates framing exposure and argues for nail-fin replacement with re-flashing rather than a retrofit insert that conceals it.

Sticking or hard-to-operate sliders

Usually rollers, track debris, or a racked frame. Rollers are a wear item and are frequently replaceable. If the frame is out of square from settlement, operation will not be restored by hardware.

Drafts and noise

Sliding-seal windows leak more air than compression-seal casements. For acoustic complaints, laminated glass and dissimilar pane thicknesses do more than gas fill. Air sealing at the frame-to-wall joint is often the larger contributor.

Repair or replace