Do My Windows Need Replacing? Condensation, Drafts, Rot and the Honest Timeline

Windows fail slowly, which is why most homeowners live with bad ones for years. The fog between the panes becomes normal, the towel on the sill in January becomes normal, and the room nobody sits in because it is cold becomes the room nobody sits in. Here is how to tell what your windows are actually doing, what each problem costs to fix, and when replacing is the right call.

The five signs, and what each one means

• Fog, streaks or a white haze between the panes. The seal on the insulated glass unit has failed. The window now insulates about as well as single pane and the haze only gets worse. On a sound vinyl or fiberglass frame, the glass unit alone can be swapped for $250 to $600. On an aluminum or rotting wood frame, it is the sign to replace the window.
• Condensation on the inside surface in winter. Different problem. This is warm indoor air hitting cold glass, and it usually means single-pane glass, aluminum frames that conduct cold, or a bathroom and kitchen that are not venting. Single pane and aluminum are replacement candidates; a venting problem is a fan.
• Drafts and cold spots. Feel the edges of the frame on a cold, windy evening. Air at the sash means failed weatherstripping, a $30 fix. Air at the frame edge, where the window meets the wall, means the installation was never sealed or the frame has moved, and that is a replace-and-reflash job.
• Soft wood, dark stains or peeling paint at the sill. Water is getting in and staying. Probe the sill and the bottom of the frame with a screwdriver; if it sinks in, the frame is rotting and the question is whether the wall framing behind it is too. This is the one sign that should not wait.
• Sashes that stick, drop or will not lock. Broken balances in a double-hung are a $100 to $200 repair on a window worth keeping. A sash that has warped out of square is a window at the end of its life.

Repair or replace: the honest rule

One failed seal, one broken balance or a draft at the weatherstripping on an otherwise sound window is a repair. Rot anywhere in the frame, aluminum frames, single-pane glass on a heated wall, or three or more windows with failed seals is a replacement project, because by the time a third seal has gone the rest are on the same clock. Windows installed in the same year fail in the same few years, which is why 1990s vinyl windows across Lynnwood and Bothell are all fogging at once in 2026.

The cost side is in our window replacement cost guide: insert replacements at $700 to $1,400 per window keep the existing frame, full-frame at $1,200 to $2,500 removes it and reflashes the opening. If there is any rot, it has to be full-frame, because an insert over a rotten frame hides the problem and keeps it wet.

What Western Washington does to windows

Wind-driven rain on south and west elevations finds every gap in the flashing, and a window that was installed without a sill pan or with the house wrap lapped the wrong way leaks into the wall for years before the drywall shows a stain. When we pull a failed window in Edmonds or Mukilteo we often find the framing wet below it, and sometimes the sheathing gone. That is why full-frame replacement on an exposed elevation is money well spent, and why our window replacement page talks about flashing before it talks about glass. The same water usually shows up in the siding; our guide to whether siding needs replacing covers the companion symptoms.

Timing

Drafts, rot and single pane are worth fixing before the heating season, and late fall into winter is when installers have the shortest lead times. Failed seals on a sound frame can wait for a dry-weather glass swap. If a kitchen or bathroom remodel is coming, do the window in that room with the remodel; the opening is already being worked on. Our fall exterior checklist puts the window probe on the calendar with the gutters and the roof, and the exterior painting guide explains why new windows and a repaint are usually sequenced together.

Who to call

A window company sells windows. A general contractor who also does siding sees the wall around them, which is where the real damage lives. ENF replaces windows across Everett, Edmonds, Lynnwood and the rest of Snohomish and King County, and if a window comes out and the framing is wet, the fix is in the same contract rather than a second project. The estimate is written, per window, with insert and full-frame priced side by side.

Get the windows checked →