Windows · Common problems · Updated November 2026
Window Condensation: Between the Panes vs. on the Room-Side Glass
Condensation on windows can mean very different things depending on where it forms. Fog on the room side points to indoor humidity. Fog between the panes means the window's seal has failed.
How to tell them apart
Wipe the glass on both sides with a dry cloth. Where the moisture stays tells you where it is.
| Where it forms | How to check | What it usually means |
|---|---|---|
| Room-side glass | Wipe it with a cloth; it comes right off | Indoor humidity meeting cold glass |
| Between the panes | Wiping either side does nothing; may leave a film or haze | Failed insulated glass seal |
| Outside surface | Wipe from outside; burns off as the day warms | Normal with efficient glass on cool, humid mornings |
| Ice or frost on the room side | Common in very cold weather | High humidity, very cold glass, or weak frames |
Room-side condensation: what to do
- Measure indoor humidity; in cold weather, lower levels help (measuring humidity).
- Run bath and kitchen fans during and after use.
- Open blinds and curtains so warm air reaches the glass.
- Check that the dryer vents outside and humidifiers are not set too high.
- Persistent wet sills can rot wood; dry them and watch for mold.
If it is between the panes
Fog between the panes means the insulated glass seal has failed, and it will not clear on its own. It is not usually urgent. For repair choices, costs and warranty questions, see foggy windows: repair or replace.
Cost figures are national ranges from the sources listed in our windows cost guide, not a quote from FixFinch or any contractor. This article is general information to help you decide on next steps. It is not an inspection or professional advice; a qualified pro who sees the problem in person can tell you what is actually going on. Calls connect you with an independent service provider in our network. FixFinch is not a contractor and does not perform the work.