How to Stop Condensation on Windows Inside Your Home

Warm air holds more water vapour than cold air. Every home produces a lot of it: cooking, showers, drying clothes indoors, kettles and even breathing overnight. When that warm, damp air touches a cold surface, it cools and drops its moisture as water. Glass is usually the coldest surface in the room, so that is where it shows first.

Condensation is worst in bedrooms in the morning, kitchens and bathrooms, and rooms with drying laundry. It is often worse after new windows are fitted, because the house becomes more airtight and moisture has fewer ways out.

The most effective fix is to let damp air out before it settles on the glass. Use extractor fans while cooking and showering, and leave them running for a while afterwards. Keep the kitchen and bathroom doors closed so the steam does not spread to colder rooms.

Open a window a little for ten or fifteen minutes in the morning, especially in bedrooms. A short burst of fresh air clears damp air quickly without chilling the house for long.

Many modern windows have trickle vents in the top of the frame: small slots with a sliding cover. Left open, they let a steady, gentle flow of air into the room, which helps carry moisture away. They are designed to stay open most of the time.

If your vents are stuck, snapped or missing their covers, they can be replaced. A vent check is often part of a window seal replacement visit.

Cold rooms collect condensation fastest. Keeping the heating on low and steady through the day usually works better than short bursts of high heat. Try not to leave spare rooms unheated with the doors shut, as they become cold traps for damp air from the rest of the house.

Curtains and blinds pulled tight to the glass trap cold air against the window overnight. Leaving a gap at the top and bottom lets warm room air reach the glass.

• Dry washing outside or in a vented dryer where possible
• Put lids on pans while cooking
• Wipe the glass and sills each morning with a cloth or squeegee
• Move furniture slightly away from cold outside walls
• Consider a dehumidifier in rooms that stay damp

Ordinary condensation is not a window fault, but some window problems make it worse. Worn seals let cold draughts chill the frame edges. A sash that has dropped may leave a cold gap. Old single glazing or failed units have a colder inner surface. In those cases repairing the window helps alongside better ventilation.

If the haze is between the panes and cannot be wiped, no amount of ventilation will clear it. That unit has failed and needs replacing; see misted double glazing.

Some people notice condensation on the outside of the glass on cool, clear mornings. That is normal with energy efficient glazing and shows the window is keeping heat inside. It clears as the day warms up.