What goes wrong with a window

Symptoms first, quotes second

Most expensive window mistakes start with a symptom described to a salesperson. The table maps the common symptoms to their usual cause — the diagnosis an installer should confirm before pricing a fix.

Symptom	Usual cause	What it usually means
Broken or cracked pane	Impact, thermal stress, or a failed seal	Glass-only repair if the frame is sound
Fog or condensation between panes	Failed insulated glass unit seal	IGU replacement, not a whole window
Drafts and cold spots	Failed weatherstripping, sash or frame decay	Seal repair first, replacement if the frame has moved
Rot or swelling at the sill	Water entry, failed flashing, no drip edge	Full-frame, because the frame is the failure
Hard to open or close	Warped sash, failed balance, painted shut	Hardware or sash repair, rarely replacement
Outside noise and UV fading	Single glazing, no laminated or coated glass	Glass package change, not a full tear-out
Faded or peeling frames	UV exposure on vinyl, or failed paint on wood	Cosmetic until the frame itself fails
Condensation on the inside face	Interior humidity, not a window fault	Ventilation and humidity first

What to document before you call anyone

Photographs of the inside and outside faces, plus a close-up of the sill.
When it started, and whether it changes with weather or season.
Whether the fogging is between the panes or on the room-side surface.
Previous work: who did it, when, and with what unit.
The frame material and the approximate age of the window.

What not to do first

Do not accept a full-replacement scope before the frame has been inspected with the trim off. Patching a symptom over a rotted frame is how the same problem returns in three years with a bigger invoice. The methods hub explains what each fix addresses; the cost hub shows what it should cost.

When is it urgent?

When water is entering the wall assembly, when glass is broken and reachable, or when a window is the only egress from a bedroom and will not open. Everything else can wait for a second opinion.

Should I get an independent inspection?

For anything above about $5,000, or any job where rot is suspected, yes. A few hundred dollars for an independent report is cheaper than a wrong scope on a whole-house job.

Can I replace just the glass?

Often yes. If the frame and sash are sound, a glass-only or IGU-only replacement costs a fraction of a new unit. The cost hub carries that line separately.