# Problems guides

> What goes wrong: independent, numbers-first guidance from Window Replacement Lab.

Canonical: https://windowreplacementlab.com/problems/

Last updated: 2026-11-08

## 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](/methods/) explains what each fix addresses; the [cost hub](/cost/) 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](/cost/) carries that line separately.