What Sweating Windows Usually Mean

People say the windows are sweating and mean the glass is wet on the room side. The house is not raining inward. Moisture in the air is condensing on a cold surface, the way a cold drink sweats on a humid day. In winter the glass is the cold drink. The amount of sweating tracks how much moisture you keep indoors and how cold the pane is.

A small gauge is the tool that keeps this from becoming a debate about window brands. Read it in the morning in the worst room. Under about 50 percent is a solid aim. Above that, on a cold day, sweating is likely even with decent windows. Below that, if one window still pours, look at that window for a leak, a failed seal, or a single pane that is simply colder than the rest.

The moisture you can change is ordinary. Showers without a fan that exhausts outdoors. A dryer vent that does not really reach outside or that is clogged. A humidifier set and forgotten. Lots of cooking with no range fan. A wet basement or crawl space sharing air. Line those up before you shop for glass. Many sweating houses get quieter when the bath fan runs 20 to 30 minutes and the humidifier is turned down.

Wipe sills so the message does not become rotten wood while you experiment. Soft wood is past the experiment. A carpenter should see punky sills. Painting over them is a cover.

Fog trapped between panes is not sweating you can wipe. That is a failed seal. Say so when you ask for help, or you will get a humidity lecture for a dead glass unit.

Sweating that only happens in one bathroom window after showers is a fan story. Sweating in every bedroom on cold mornings is a house story. Write which pattern you have. The fix follows the pattern.

Do not block combustion air or seal a furnace room shut to "keep humidity in" or out. Burning appliances need their air. If you smell gas, leave and call the gas utility from outside.

Give the house a week of honest fan use and a turned-down humidifier before you call a window company. Take morning photos of the same pane. You want to see whether the beads shrink when the gauge drops. If they do, you have leverage that does not require new frames. If the gauge is already reasonable and the beads stay heavy on one window, that is the window to ask about.

Storm windows and shrink film change the temperature of the surface you see. Look at the sill anyway. Some coverings move the condensation to a hidden face. A dry-looking room with a wet sill behind a blind is the same problem with better camouflage.

Track one number and one habit, not ten. The morning gauge and whether the bath fan ran are enough for the first week. If both are fine and the glass still weeps in every room, widen the hunt to the dryer and the lower level. Start narrow so you know what changed.

If you only change one thing this week, run the bath fan long enough and read the gauge in the morning. Leave the window quotes for the week after. Sweating that fades when the number drops is a moisture habit. Sweating that stays while the number is already reasonable belongs to that pane. You will spend less if you let those two outcomes show themselves before you buy glass.

This is a house check, not a diagnosis. Symptoms go to a doctor, and big wet repairs go to a licensed pro.

Sweating glass is explained in pictures in When Your House Doesn't Feel Right. $2.99 at https://clearnestair.com/book.