Every autumn, the same morning ritual comes back to thousands of Manchester homes: wiping pools of water off the sills before the mould beats you to it. Sound familiar? Condensation is the UK's most common window complaint, and one of the most misdiagnosed, because the same word covers three different problems with three different fixes.
Where the moisture sits tells you almost everything. Let's decode it.
First, find where the water is
| Where the condensation sits | What it means | Severity |
|---|---|---|
| Inside face of the glass (room side) | High indoor humidity meeting a cold surface | Fixable with habits + ventilation |
| Between the two panes | Failed sealed unit, desiccant saturated | Glass unit needs replacing |
| Outside face of the glass | Highly efficient glazing on a cold clear night | Not a problem at all |
Condensation on the inside: your air, not your windows
An average family puts 10-15 litres of water vapour into the air every single day. Cooking, showers, kettles, clothes drying indoors, even breathing. That vapour stays invisible until it touches a surface below its dew point, and in most rooms the coldest surface going is the glass. Old, poorly insulated glazing makes things worse, because colder glass means more condensation, but the root cause is moisture with nowhere to go.
The habits that fix most cases
- Lids on pans, extractor running while you cook and for ten minutes after
- Bathroom extractor on for every shower, door shut, window cracked open afterwards
- Dry clothes outdoors, in a vented tumble dryer, or in one room with the door closed and the window open. Never on radiators around the house
- Keep trickle vents open all year round; this is exactly what they're for
- Hold steady background heat in cold snaps instead of blasting hot-cold cycles
- Leave a small gap between furniture or curtains and external walls so air can circulate
Still damp after the habit changes? A humidistat extractor or a positive-input ventilation unit tackles the problem at whole-house level, and it costs less than redecorating mouldy reveals every other year.
Condensation between the panes: a failed unit
Mist you can't wipe means the sealed unit's perimeter seal has gone and the desiccant inside is saturated. No ventilation habit will touch it; the unit needs replacing. The good news? If the frame is sound, it's a glass-only job rather than a new window. We cover causes, costs and options in our misted double glazing guide, and our glass replacement service makes replacement units in our own Trafford Park factory.
Condensation on the outside: oddly, a compliment
Dew on the outside of the glass on a clear morning means your glazing insulates so well that the outer pane stays cold. That's exactly what an A++ window is supposed to do. It burns off as the day warms up and needs no action from you whatsoever.
When condensation is telling you the windows are done
If internal condensation carries on despite good ventilation habits, the glazing surface is probably just too cold. Single glazing, usually, or early double glazing that's degraded. Modern low-E units keep the inner pane several degrees warmer, which lifts it above the dew point in a normal household. Seeing draughts, misted units and tired frames as well? Weigh the evidence against our 10 signs you need new windows checklist, and remember that new windows come with trickle vents that solve the ventilation half of the equation at the same time.
Don't ignore the mould
Black spotting on reveals, sills and curtains is more than a cosmetic nuisance. Mould spores aggravate asthma and other respiratory conditions, and under Awaab's Law social landlords are now legally required to deal with damp and mould hazards promptly. Kill surface mould with a fungicidal wash, then fix the moisture source, or it'll be back within weeks. Persistent mould around window reveals sometimes points to failed perimeter seals letting rain track in; our repair team can rule that out in a single visit.
A one-week condensation action plan
- Day 1-2: Diagnose. Check every affected window: wipeable moisture inside, fog between the panes, or dew outside? Note down which windows have which.
- Day 3: Cut moisture at source. Lids on pans, extractors on, clothes drying moved out of living spaces, trickle vents opened.
- Day 4: Treat any existing mould with a fungicidal wash so you can tell whether it comes back.
- Day 5-7: Watch the pattern. Habit-driven condensation improves within days. Windows still streaming after the changes are telling you the glass surface is too cold, or that the units have failed.
Reach the end of the week with the same windows soaking every morning? Get them surveyed. There's no prize for wiping sills until spring, and if the answer turns out to be a couple of replacement units rather than new windows, far better to hear that from an honest survey than to assume the worst.
Manchester's climate keeps this a live issue for longer than most of the country. Our heating season runs deep into spring, and mild, humid winters keep indoor moisture high. Yet the households that beat condensation aren't the ones with special gadgets. They're the ones that ventilate consistently and act on failed glazing instead of living with it. Both cost pennies compared to redecorating mouldy rooms every couple of years.
Frequently asked questions
Why do my windows have condensation every morning?
Overnight, humidity from cooking, showers and breathing meets glass that's cooled below the dew point. Cut moisture at source, ventilate consistently, and if it still persists, modern glazing with a warmer inner surface is the longer-term fix.
Does condensation mean my double glazing has failed?
Only if the mist sits between the panes where you can't wipe it. Moisture on the room side is a humidity problem, and moisture on the outside means your glazing is working well.
Will new windows stop condensation?
Largely, yes, on the glass itself. Low-E units keep the inner pane warmer, and built-in trickle vents improve background ventilation. In a very humid home the moisture may simply find the next coldest surface, so your ventilation habits still matter.
Are trickle vents worth having open in winter?
Yes. The heat lost through a trickle vent is small, while the condensation and mould that closed vents cause cost far more. Building regulations now require them in most replacement windows for exactly this reason.
Is window condensation harmful?
The water itself isn't, but sustained condensation feeds black mould, rots timber sills and stains plaster. Mould is a genuine health hazard, especially for children and asthma sufferers, so persistent condensation is worth fixing rather than just wiping.
Will a dehumidifier stop condensation on windows?
It helps. A decent dehumidifier in the worst-affected room pulls litres of moisture out of the air and takes the edge off wet mornings. Treat it as management rather than cure, though: it costs electricity to run daily and it can't warm cold glass. Fix the moisture sources and ventilation first, and let the dehumidifier be the top-up, not the strategy.
Wet windows every morning?
Send us a photo and we'll tell you within minutes whether you're looking at a ventilation fix, a failed sealed unit, or glazing that's simply had its day. Repairs and replacement units made in Manchester, fitted across the North West.
Call 07533 830717, WhatsApp us a photo for a fast quote, or request a free quote online.