Buying Guide
Condensation on Windows — How to Stop It UK Guide
Updated August 2026
Condensation on windows is the most searched damp problem in the UK — and the most fixable. Whether it appears overnight in bedrooms, after cooking in kitchens, or all day in bathrooms, the cause is always the same: warm moist air meeting cold glass. Here are 8 ways to stop it, from free to permanent.
Quick answer
Our top pick: Trickle vents + absorber strips + a dehumidifier at 50% RH
£0 – £200 on Amazon
Free fix: open trickle vents and bedroom door at night. Cheap fix: absorber strips (£6) + anti-fog spray (£10). Permanent fix: dehumidifier set to 50% RH (£85-200).
Check Price on Amazon →Why condensation forms on windows
Air holds a limited amount of water vapour, and that limit falls sharply as the air cools. Glass is the coldest surface in almost every UK room, so it is where air first cools past its dew point and releases moisture as liquid water.
A normal household generates a surprising amount of vapour: roughly 1 litre per night from two sleeping adults, 1–2 litres from cooking a meal, 1.5 litres from a shower and up to 5 litres from drying a load of washing indoors. If that moisture cannot get out of the building, it ends up on your windows.
So there are only ever three levers: make less moisture, get moisture out of the air, or make the glass less cold. Everything below is one of those three.
8 fixes, cheapest to most effective
- Open your trickle vents (free). Most UPVC windows have them and most people have them shut. Leaving them open costs a negligible amount of heat and continuously removes moist air.
- Leave the bedroom door ajar at night (free). It lets moisture disperse into the rest of the house instead of concentrating on one cold pane.
- Ventilate hard for 10 minutes each morning (free). Windows wide open, doors shut. Fast air exchange dumps the moisture without cooling the walls.
- Stop drying laundry on radiators (free). A single load releases up to 5 litres of water into your home. Dry it in one room with the door shut and a dehumidifier running.
- Absorber strips on the frame (£6). They sit along the bottom of the pane and soak up the run-off so it never reaches the sill or the seals.
- Anti-fog spray on the glass (£10). Rain-X style treatment makes moisture sheet off rather than mist, keeping the view clear and the sill drier.
- Thermal curtains or secondary glazing film (£12–£40). Warms the room side of the assembly. Fit film to single glazing and condensation often disappears entirely.
- Dehumidifier set to 50% RH (£85–£200). The permanent answer. Keep the room below 55% RH and the glass rarely reaches dew point at all.
Products that actually stop window condensation
FuKuEn Window Condensation Absorber Strip
Not a cure, but it stops water pooling on the sill and rotting the seal — which is what actually causes mould around a window frame.
Pros
- Catches run-off before it reaches the sill
- Self-adhesive, fits in minutes
- Washable and reusable
Cons
- Manages the symptom, not the cause
- Needs wringing out on bad mornings
Who it's for: Rented flats where you cannot change the windows
Check Price on Amazon UK →Rain-X Anti-Fog Treatment
Water sheets off instead of misting, so the pane stays clear and the moisture that does form runs to the strip rather than sitting on the glass.
Pros
- Keeps glass clear for weeks per application
- Works on mirrors and bathroom glass too
- Very cheap per window
Cons
- Needs reapplying every few weeks
- Doesn't reduce room humidity
Who it's for: Bathroom mirrors and windows you need to see through
Check Price on Amazon UK →Kärcher WV2 Window Vacuum
If you are already wiping windows each morning, this turns a ten-minute chore into a thirty-second one and actually removes the water from the room.
Pros
- Clears a whole window in seconds
- No dripping towels or wet sills
- Also good for shower screens and tiles
Cons
- Needs charging
- A daily job, not a fix
Who it's for: Homes with heavy morning condensation on several windows
Check Price on Amazon UK →BKSAI Secondary Glazing Window Film
The only item here that attacks the cold-surface side of the equation. On single glazing the difference is dramatic.
Pros
- Raises the temperature of the room-side surface
- Often eliminates condensation on single glazing
- Removable — renter friendly
Cons
- Fiddly first fit
- Window cannot be opened once sealed
Who it's for: Single-glazed or old timber windows in cold rooms
Check Price on Amazon UK →Devola 12L Dehumidifier
Set it to 50%, shut the door, and window condensation simply stops happening. Roughly 5p an hour to run at current UK rates.
Pros
- Humidistat holds the room at 50% RH
- Covers rooms up to 20m²
- Laundry mode for indoor drying
Cons
- Around 42dB — audible at night
- Tank needs emptying
Who it's for: Anyone who wants condensation gone rather than managed
Check Price on Amazon UK →Deconovo Thermal Curtains
Good for warmth, but open them in the morning — leaving them shut all day traps cold air at the pane and makes condensation worse, not better.
Pros
- Cuts heat loss through the window
- Also blocks light and noise
- Wide range of sizes
Cons
- Can trap cold air against the glass if fully sealed
- Need opening in the morning
Who it's for: Cold bedrooms and living rooms
Check Price on Amazon UK →ThermoPro TP50 Hygrometer
Buy this first. If the room sits above 60% RH you have a humidity problem; below 55% and condensation is largely a cold-glass issue instead.
Pros
- Shows RH and temperature at a glance
- Records daily high and low
- Under a tenner
Cons
- No app or logging
Who it's for: Knowing whether your fixes are working
Check Price on Amazon UK →Kitchen vs bedroom vs bathroom condensation
Bedroom. Slow overnight build-up from breathing. Trickle vents open, door ajar, 10 minutes of morning ventilation, and a dehumidifier if it persists. Full bedroom guide →
Kitchen. Short, intense bursts while cooking. Lids on pans, extractor on before you start and for 15 minutes after, and keep the door shut so the steam does not migrate into cold bedrooms.
Bathroom. The worst offender per minute. Run the extractor during and 20 minutes after every shower, wipe the glass down, and keep the door closed. Extractor fan guide →
When to worry about condensation
- Black mould spreading on the frame, seals or nearby wall.
- Condensation between the panes — the sealed unit has failed.
- Damp patches or a tide mark low on the wall, which suggests rising or penetrating damp.
- Peeling paint, blown plaster or a persistent earthy smell.
- Humidity staying above 70% RH even with a dehumidifier running.
If you rent and any of the above apply, your landlord has legal duties under Awaab's Law. Your landlord's responsibilities →
Buying advice
Measure before you spend
Tip
Short and sharp beats windows on the latch
Warning
Never block trickle vents
Frequently asked questions
Bundle
Window Condensation Kit — Under £120
- ThermoPro TP50 hygrometer£10Amazon →
- FuKuEn absorber strip£7Amazon →
- Rain-X anti-fog treatment£10Amazon →
- Devola 12L dehumidifier£95Amazon →