Why Do I Get Condensation on My Windows Every Morning?

Wet windows in the morning is one of the first things people notice when the cold weather comes in. Overnight the heating goes off, the glass cools down, and the warm, moist air in the bedroom hits it. Two people sleeping in a closed room put a fair bit of moisture into the air through breathing alone, and it has to go somewhere.

A little condensation on the inside of the glass on a frosty morning isn’t a disaster. What you don’t want is windows streaming every day, water pooling on the sills, and black mould starting on the seals, frames and window reveals. That’s telling you the moisture level in the house is too high for the temperature it’s being kept at.

What helps

• Keep the trickle vents open, day and night, all year. They’re there for a reason.
• Open the bedroom window a crack for ten minutes when you get up, and wipe the glass and sills dry with a cloth or a window vac. Wring the cloth out down the sink, not back on the radiator.
• Keep bedroom doors open at night if you can, so moisture spreads out rather than concentrating in one cold room.
• Keep the heating at a low, steady level overnight in cold spells rather than letting the house go stone cold.
• Dry washing outside or in a vented or heat pump dryer, not on the bedroom radiator.
• Use the kitchen and bathroom extractor fans properly, so that moisture doesn’t drift upstairs.

Older single glazing and aluminium frames run colder than modern double glazing, so they’ll always attract more condensation. If you have condensation between the two panes of a double-glazed unit, that’s a different problem: the seal on the unit has failed, and the unit needs replacing. It isn’t a damp issue in the house.

If you’ve done all of the above and the windows are still running wet every morning, the house may need mechanical ventilation, such as a PIV unit or continuous-running extract fans. It’s also worth checking there isn’t another moisture source, like a damp subfloor or a leak, feeding the air.