Check whether the moisture is on the room side, between the panes or around the frame, reduce ordinary humidity, and report staining, failed glazing or recurring dampness.
Condensation is water from warm, humid indoor air meeting a colder surface. That is different from rain entering around the frame or moisture trapped between double-glazed panes. The location, timing and texture of the water provide the first useful clues.
Start with a dry cloth and a photograph. Do not seal drainage holes, remove glazing beads or apply permanent caulk as a first renter fix. For moving air around the sash, use the drafty-window guide separately.
Dry standing water promptly and move items away from the frame. If the wall or trim is soft, stained, moldy or wet after rain, report the source rather than treating it as ordinary steam.
Find where the water is
Run a clean finger or tissue along the room-facing glass, the frame, the sill and the wall reveal. Water on the room side of the glass is often condensation. Water between panes may indicate failed glazing. Water on the wall or trim after rain points to a sealing or building issue.
Note whether the water appears after showering, cooking, sleeping, cold weather or rain.
Capture the same area before wiping, then check for stains, peeling paint or swollen trim.
A repeating pattern is more useful than a one-off wet morning.
Reduce ordinary indoor humidity
Use bathroom and kitchen exhaust fans as intended, dry wet clothes where they can ventilate, keep furniture from blocking warm air at the window and wipe the sill when condensation appears. If you own a humidity meter, record the reading rather than guessing.
EPA explains that condensation forms when warm humid air meets a cold surface and recommends reducing indoor humidity, increasing ventilation and drying wet surfaces. It also advises renters to report plumbing leaks and moisture problems to the building owner or manager (US EPA: Ways to control moisture).
Check the frame without altering it
Look for blocked drainage openings, cracked trim, failed paint, a misted glass unit or a sash that does not latch. Do not poke into drainage channels, tape over exterior openings or apply expanding foam. Keep the window able to open if it is an escape or ventilation route.
If the condensation is only on the room side and improves with normal ventilation, keep documenting the pattern. If it returns despite ordinary moisture control, the room has a cold bridge or the window assembly may need maintenance.
Know when window condensation needs a report
Report the window if water appears between panes, rain enters, the wall or trim stays damp, mold returns, paint peels, the frame is cracked, the sash will not latch, or the condensation appears in several rooms despite normal ventilation. Mention whether the moisture is on glass, frame, wall or sill.
“Condensation appears on the [room] window after [showering/cold nights/rain]. It is on the [room-side glass/between panes/frame/wall], and the sill is [dry/damp/stained]. I dried and photographed it, and the window [does / does not] latch normally.”
Keep the sill from becoming a mold source
Dry the sill, keep curtains or blinds from trapping wet air against the glass, and avoid storing books, fabric or cardboard on a damp ledge. Do not paint over staining or place a seal across the bottom drainage path.
For a move-out record, keep the dated photos and link any report to the window location. The move-out guide collection can help you separate a documented condition from a cosmetic cleaning task.
Compare weather, glass and frame
Window condensation needs a location and a pattern. Dry the sill, reduce ordinary humidity, avoid sealing the frame blindly and report water between panes, rain entry or recurring dampness. Continue with the full guide library for the next practical check.
These links support specific safety, maintenance or jurisdiction examples in the article. General guidance cannot replace the instructions for the exact appliance, fitting, lease or location.