Condensation on windows in winter is common in UK homes, and you can stop it by cutting indoor moisture and keeping air moving. The best fixes are ventilating with trickle vents and extractor fans, keeping heating steady, and using a dehumidifier in damp rooms. Daily habits like lids on pans and drying laundry outside also help.
In this guide, we explain why windows steam up in the cold months and walk you through practical steps that work in real British homes. We start with one step no other UK guide mentions: measure your humidity first.
Step 0: Measure Your Humidity First
The smartest first step costs under a tenner. Buy a small hygrometer and put it in your bedroom, away from the radiator and the window.
Aim for 40 to 60 percent through winter. Above 60 percent you get condensation, and above 70 percent mould starts to grow. If your mornings read 65 percent or higher, moisture is your problem, not your windows. Recheck as you apply these fixes.
Why Do Windows Get Condensation in Winter?
Condensation forms when warm, moist air touches a cold surface. Window glass is usually the coldest surface in a room, so it acts like a magnet for moisture in winter.
Cooking, showering, drying clothes indoors and even breathing release water vapour. When heating drops at night and the glass cools, vapour turns to droplets. Double glazing helps, but it cannot remove moisture from the air.
Diagnose First: Inside, Outside or Between the Panes?
Check where the moisture sits before spending money on fixes. Each type means something different.
- Outside of the glass. Common on cool mornings. Your glazing is doing its job. Ignore it.
- Inside of the glass. The classic winter problem. Warm, moist indoor air is hitting cold glass. The fixes below will solve it.
- Between the panes. The seal has failed. No ventilation fix will help. Get the glass unit resealed or replaced.
Is Window Condensation Harmful?
A light mist that clears quickly is normal. The problem starts when water pools on sills every day and sits for hours.
Persistent damp feeds black mould on frames, seals and nearby walls. It stains paint, rots sills and leaves a musty smell. Mould spores can aggravate allergies and asthma, especially in bedrooms. If you see dark patches, act promptly. Our guide on how to remove mould from a bathroom ceiling covers safe cleaning methods that work on window reveals too.
How to Stop Condensation on Windows in Winter
The permanent fix has two parts: produce less moisture and ventilate more. Work through these steps in order, starting with the free and easy ones.
1. Ventilate Properly
Fresh air carries moisture out. Keep trickle vents open through winter. Use extractor fans every time you cook or shower, and leave them running 15 to 20 minutes afterwards. A humidistat fan, which switches itself on and off with moisture, is a smart upgrade for a weak bathroom fan. For ideas, see our toilet ventilation ideas, from window fans to full systems.
Open bedroom windows for five to ten minutes each morning. A short burst of cold air dries the room far better than a window cracked all day.
2. Keep Heating Steady
Big temperature swings make condensation worse. When rooms cool right down overnight, morning misting is almost guaranteed. Keep a low, steady background heat across rooms.
3. Use a Dehumidifier
A dehumidifier pulls moisture straight from the air and suits bedrooms, kitchens and drying rooms. Run it in the dampest room with the door closed, and empty the tank regularly. In unheated conservatories, a desiccant model beats a compressor type.
4. Cut Moisture at the Source
Put lids on saucepans and keep the kitchen extractor on. Close the bathroom door while showering. Dry laundry outside when you can, or use one room with the window cracked and the door shut. Never drape wet washing over bedroom radiators.
5. Let Air Circulate
Keep furniture a few centimetres from external walls and avoid piling clothes under windows. Open curtains and blinds by day so warm air reaches the glass. Heavy curtains shut all day keep the window cold.
Trickle Vents: The Detail Nobody Gives You
A trickle vent is a narrow slot at the top of the window frame with a small sliding cover. It gives background ventilation around the clock without the draught of an open window.
Look for a slim vent cover along the top of the frame. Most double glazed windows fitted since the early 2000s include them. Check they are open, not painted shut. Ease any painted cover free with a craft knife.
Wipe the slot with a damp cloth every few months, since dust and cobwebs block it. They let in far less air than an open window, and damp air costs more to heat than dry air, so the small heat loss is worth it. No trickle vents? A glazier can usually retrofit them for far less than a dehumidifier costs.
The Bedroom Night-Time Routine
Bedrooms suffer worst: two people breathing all night pump moisture into a closed, often cool room.
Before bed: open trickle vents fully, leave the door ajar, keep heating low and steady, and keep damp clothes off the radiator.
In the morning: open curtains straight away, wipe or vacuum the glass and sills, open the window for ten minutes, and check the hygrometer. It should be falling back towards 40 to 60 percent.
Your First 7 Days: An Action Plan
Day 1: buy a hygrometer, wipe every window and sill, open all trickle vents. Day 2: set extractor fans to run 15 to 20 minutes after showers and cooking. Day 3: move furniture from external walls, open curtains each morning. Day 4: dry laundry in one room, window cracked, door shut. Day 5: check the hygrometer and add a moisture trap or dehumidifier where readings stay above 65 percent. Day 6: clean mould spots safely (see below). Day 7: review and keep what worked.
What Each Fix Costs
Start free and spend only if you need to. Prices vary by brand and region.
| Fix | Typical cost | Best for |
|---|---|---|
| Daily habits: airing, lids on pans, wiping glass | £0 | Every home |
| Disposable moisture traps | Around £4 each | Small damp spots |
| Window vacuum | Around £39 | Quick morning clear-ups |
| Electric dehumidifier | £120 to £250 plus running costs | Damp rooms |
| Positive input ventilation (PIV) | £800 to £1,500 fitted | Whole house, owners |
| Heat recovery ventilation (MVHR) | £3,000 plus fitted | New-builds, retrofits |
How to Clear Condensation Each Morning
Until the longer term fixes take effect, clear the glass daily: wipe top to bottom with a microfibre cloth or squeegee, wring it into the sink, dry the sill with a separate cloth, then air the room for five to ten minutes.
Mould Has Already Appeared? Clean It Safely
Wear rubber gloves and open the window. Wipe mould with a cloth dampened with warm soapy water or a mould remover, following the label. Never dry brush mould, as that throws spores into the air. Bin the cloth or wash it hot.
Asthma or allergy sufferers should ask someone else to clean and stay out until the room has aired. Call a professional if mould keeps returning, covers a large area or grows inside walls.
Renting? In a New-Build? Read This
Renters: you cannot fit PIV or MVHR and should not alter windows without permission. Most fixes here are still yours to use: trickle vents, extractor fans, daily wiping and careful drying. Report broken fans and persistent mould to your landlord in writing. UK landlords must keep homes free of serious damp.
New-build owners: airtight modern homes hold heat but trap moisture too. If your new-build mists constantly, mechanical ventilation is not a luxury. It is how the house was designed to breathe.
When Does Condensation Signal a Bigger Damp Problem?
Window condensation is usually a ventilation issue, but watch for water running down walls, mould spreading beyond windows, bubbling paint or a musty smell.
If your home smells damp where windows are clear, moisture may come from elsewhere. Our guide on how to get rid of a damp smell in a wardrobe or cupboard can help you track it down. Rising damp, leaking gutters and failed cavity insulation need professional attention, so call a qualified damp surveyor rather than guessing.
FAQs
Why is condensation worse in bedrooms?
Two people breathing all night release lots of moisture into a closed, often cool room. Follow the night-time routine above.
Will a dehumidifier stop condensation completely?
It greatly reduces condensation, but works best alongside ventilation and steady heating.
Can new windows fix condensation?
Warmer inner panes reduce condensation on the glass, but they do not remove moisture from the air. Without ventilation, damp moves to the next coldest surface.
Does opening windows in winter make condensation worse?
No. A short burst of cold, dry air flushes moisture out. Warm, damp air sitting still against cold glass is the real problem.
Is condensation on new windows normal?
Often. New windows are more airtight, so moisture that once escaped now stays inside. Better ventilation is the answer, not worse windows.
Does condensation mean I must replace my windows?
Rarely. Inside condensation is a ventilation problem. Only moisture trapped between the panes means the sealed unit has failed.
Conclusion
Stopping condensation on windows in winter comes down to three habits: measure your humidity, ventilate a little every day, and cut moisture where you create it. Start with the free fixes. Stay consistent, and your windows will stay clear all winter.
