Why it always seems to be first thing
Warm air holds far more water vapour than cold air. Overnight a house generates a surprising amount of it, mostly from people breathing and from drying air in bedrooms, while the heating is off and every surface slowly cools. The glass is normally the coldest surface in the room, so it is the first place the air gives up its moisture as it cools past the point where it can hold it.
By morning that has been going on for hours without ventilation, which is exactly why you find beads or a full film on the inside of the glass and a wet sill underneath. Once the heating comes on and a window is opened the room warms, the air moves, and it disappears. That daily pattern is the clearest sign that you are dealing with room humidity rather than a faulty pane.
Still wiping windows down every morning?
If ventilation and habits have not fixed it, we will survey the windows free of charge and tell you what is genuinely causing it.
Arrange a free surveyConfirm which side the water is on
Before changing anything, settle the question of where the moisture actually sits, because the fix is completely different in each case.
Wipe the inner face with a dry cloth. If it clears, that is internal surface condensation and this guide applies. If the haze is on the outside face and burns off during the morning, that is external dew and it is normal on well insulated glass. If the cloud is trapped between the panes and neither surface wipes clear, the sealed unit has failed and no amount of ventilation will change it.
- Inside face wet: room humidity, work through the causes below
- Outside face wet at dawn: dew on efficient glass, not a fault
- Between the panes: failed sealed unit, needs new glass
- Frame and reveal wet but glass dry: check for a cold bridge or a leak
Where the moisture is really coming from
Ordinary daily life puts litres of water into the air of a house. Cooking without an extractor, showers with the door left open, tumble dryers that are not vented properly and washing dried on radiators are the four biggest contributors we come across. Unvented drying is often the single worst offender because it releases the whole water content of a wash load into the air over several hours.
Bedrooms are their own case. Two adults asleep in a closed room with the trickle vents shut will noticeably raise the humidity by morning, which is why the worst condensation in most houses is on bedroom windows rather than in the living room.
- Lids on pans and the extractor running while cooking
- Bathroom door closed and the fan left on after a shower
- Washing dried outside or in a vented or condenser dryer, not on radiators
- Internal doors to unheated rooms kept shut so damp air does not migrate
- Furniture pulled a little off external walls so air can move behind it
Ventilation is the lever most people are not using
Modern homes are deliberately airtight, which is excellent for heating bills and unforgiving for humidity. If nothing removes the moisture you generate, it stays put until it finds a cold surface. That is why the most effective change is usually not more heat but more controlled air movement.
If your windows have trickle vents in the head of the frame, open them and leave them open, including in winter. They are sized to give background ventilation without a draught and they are the reason many newer windows show less condensation than the ones they replaced. If your windows have no vents at all, that is worth raising when you next have work priced, because current building regulations expectations around background ventilation have moved on considerably.
Heating patterns matter more than temperature
Short bursts of high heat followed by long cold periods are the worst combination, because the air picks up moisture while warm and then dumps it as everything cools. A lower, steadier background temperature through cold spells keeps surfaces closer to room temperature and gives the air far fewer opportunities to reach dew point on the glass.
Rooms that are never heated at all, such as a spare bedroom with the radiator off and the door closed, tend to collect the condensation from the rest of the house. Leaving those rooms slightly warmer and slightly ventilated usually improves them quickly.
When the windows genuinely are the problem
Sometimes it is the windows, and it is fair to say so. Old single glazing has nothing between the room and the outside air, so the inner surface sits close to outdoor temperature and condensation is almost guaranteed in cold weather. Early double glazing with an aluminium spacer and no warm edge technology suffers the same thing around the perimeter of the glass, which is why you often see moisture in a band along the bottom edge only.
Worn gaskets, failed hinges that stop a sash pulling up tight and blocked drainage all make it worse by leaving cold air paths and standing water. If you are wiping windows down every day, have already improved ventilation and drying habits, and it has not shifted, then the glass specification and the state of the frames are the next thing to look at properly.
- Single glazing or pre 2000 units with cold metal spacers
- Perished gaskets and sashes that no longer compress on closing
- No trickle ventilation anywhere in the room
- Persistent black mould in the corners of the reveals despite cleaning
Dealing with the mould that follows
Where condensation has been running for a while you often get black spotting on the sealant line and the corners of the reveal. Clean it with a proprietary mould treatment rather than bleach on porous surfaces, dry the area thoroughly and keep the ventilation improved, otherwise it simply returns to the same spots.
Persistent mould after all of that, especially with damp plaster rather than just surface spotting, is worth a proper look because it can point to something other than condensation.
Getting a second opinion locally
We survey free of charge across the Wirral, Chester and about thirty miles around, and we are quite willing to tell you that your windows are not the cause if that is what we find. Where the glass or frames really are contributing, we will explain which part is doing it and what a replacement would actually change.
Common questions
- Is condensation on the inside of my windows a fault?
- Usually not. Internal surface condensation is caused by humid room air meeting cold glass, so the fix normally lies in ventilation, drying habits and heating patterns rather than the window itself.
- Should I keep trickle vents open in winter?
- Yes. They are designed to provide background ventilation all year without a noticeable draught, and closing them through winter is one of the most common reasons condensation gets worse.
- Will new double glazing stop morning condensation completely?
- It reduces it considerably because the inner pane stays warmer, but it does not remove the moisture from the air, so ventilation and drying habits still matter after any replacement.
- Why is it worse in the bedroom than anywhere else?
- Sleeping adults release a lot of moisture into a closed, unheated room over several hours, so bedroom glass is often the coldest surface meeting the most humid air.
- Can condensation damage the window itself?
- Running water sitting on frames and sills for long periods can affect finishes, sealant lines and timber, and it encourages mould, so it is worth addressing rather than living with.
- Do you charge to come and look at a condensation problem?
- No, our survey is free of charge, and that includes telling you if we think the cause is humidity rather than the glazing.