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On a cold winter morning it’s common to pull back the curtains and find your windows running with water. For most homes, that moisture is completely normal. But not all condensation is the same, and where it forms tells you a lot about what’s going on.
Droplets on the inside surface of the glass usually come down to everyday moisture and ventilation. Mist trapped between the two panes of a double glazed unit is a different story: it means the seal has failed. Here’s how to tell them apart, how to cut down on window condensation in Surrey homes this winter, and when it’s time to replace a sealed unit.
Why condensation forms
Warm air holds more moisture than cold air. Cooking, showering, drying washing indoors and even breathing all add water vapour to the air in your home, and it adds up to a surprising amount every day.
When that warm, damp air meets a cold surface, it cools and the moisture turns back into water. In winter, the glass is often the coldest surface in the room, so that’s where you notice it first. Bedrooms, kitchens and bathrooms tend to be the worst, because that’s where most moisture is made.
Condensation on the inside of the glass
If you can wipe the moisture away with a cloth from inside the room, it’s surface condensation. This is the most common kind, and it’s a sign of the conditions in your home rather than a fault with the window.
Modern double glazing is well sealed to keep the heat in. That’s good news for your energy bills, but it also means damp air has fewer ways to escape. A little condensation on a frosty morning is nothing to worry about. Heavy condensation every day is worth tackling, though, because water that sits on frames and sills can lead to damp patches, peeling paint and black mould.
You might occasionally see condensation on the outside of your windows on a cold, clear morning. That’s normal too, and it often means your glazing is doing its job by keeping the warmth inside your home.
Simple ways to reduce moisture at home
Most everyday condensation can be reduced with a few small habits:
- Open your trickle vents. Many windows have small vents along the top of the frame. Keep them open, especially in bedrooms overnight and through the winter months.
- Use extractor fans. Switch them on when you cook or shower, and leave them running for a little while afterwards.
- Put lids on pans. It keeps steam out of the kitchen air and saves energy too.
- Dry washing carefully. Hang it outside when you can. Indoors, use a room with the door closed and a window ajar, and make sure tumble dryers are vented outside.
- Keep the heating steady. A low, consistent temperature keeps surfaces warmer than short bursts of heat, so there’s less for moisture to settle on.
- Air rooms each morning. Opening a window for ten or fifteen minutes lets damp air out without losing much heat.
- Wipe glass and sills. A quick wipe in the morning stops water sitting on frames and seals.
- Let air move. Keep furniture a little way from external walls, and don’t block vents or radiators with heavy curtains.
If a room stays damp despite all of this, a dehumidifier can make a real difference.
Condensation between the panes
If the mist is inside the glass and won’t wipe away from either side, the problem is the sealed unit itself.
A double glazed unit is two panes of glass held apart by a spacer bar and sealed around the edges. The gap between them is filled with dry air or an insulating gas. Over time, with age, weather and movement, that edge seal can break down. Once it does, moist air finds its way into the gap and condenses on the inner faces of the glass.
Common signs of a failed unit include:
- A milky haze or fogging that comes and goes with the temperature
- Droplets or streaks of water trapped inside the glass
- White residue or staining between the panes once the moisture dries
Unlike surface condensation, this won’t clear up with better ventilation, and it won’t fix itself. A failed unit also loses some of its insulating performance, so the area around the window may feel cooler than it used to.
A quick check: inside or between?
- Wipe the glass on the room side. If it clears, it’s surface condensation and better ventilation should help.
- If it doesn’t clear, wipe the outside of the glass. If that clears it, it’s external condensation and nothing to worry about.
- If the mist is still there, it’s between the panes and the sealed unit has failed.
Do you need a whole new window?
Often, no. If the frame, hinges and locks are in good condition, the sealed unit can usually be replaced on its own. That means less disruption and less waste than replacing the whole window.
A full replacement may make more sense if frames are rotten, warped or draughty, if several units have failed at once, or if the window no longer opens and locks properly. Either way, we’ll give you straight advice on what your window actually needs, with no pushy sales.
Local advice you can trust
Sheerwater Glass has been a family run glazing company since 1972, fitting and repairing windows, doors and conservatories for homes across Surrey and Berkshire. We’re FENSA registered and a Which? Trusted Trader, and when you call, you’ll speak to a real person, not a call centre.
Misted between the panes? Request a glass quote online or call 01932 344 415, and where possible we’ll replace just the sealed unit rather than the whole window.
