How to Stop Condensation on Windows in Winter (UK Guide)

Waking up to rivers running down the inside of your windows? Condensation on windows in winter is Britain’s most common cold-weather household complaint — and while a little misting is normal, streaming windows can lead to mould, damaged frames and peeling paint. Here’s how to stop it.

Why it happens

Condensation forms when warm, moist indoor air hits a cold window surface. UK homes generate litres of moisture daily: breathing, cooking, showering, drying clothes indoors. Modern double glazing and draught-proofing keep heat in — but also trap moisture in. Older single-glazed windows condense first because the glass is coldest.

A bit of morning misting that clears by midday is normal. Water pooling on sills, running down walls, or black mould around frames means you need to act.

The three-pronged fix: heat, ventilate, reduce moisture

1. Ventilate (the biggest lever)

• Open trickle vents on windows — that’s what they’re for. If your windows lack them, consider retrofitting (£10–£20 per window).
• Use extractor fans in kitchen and bathroom — and leave them running 15–20 minutes after cooking/showering. If your fan is weak or noisy, replace it (£80–£150 fitted).
• Open a window briefly after showers and while cooking — 10 minutes of ventilation beats hours of sealed dampness.
• For persistent problems, a PIV unit (positive input ventilation, £400–£800 fitted) gently pushes dry loft air through the house — very effective in flats and bungalows.

2. Reduce moisture at source

• Lids on pans when cooking — obvious, rarely done.
• Dry clothes outside or in a vented tumble dryer. Drying a load indoors on radiators releases ~2 litres of water into the air. If you must dry indoors, use one room with the door closed and window cracked — or a dehumidifier (£120–£200; costs ~30p/hour to run and genuinely works).
• Keep the bathroom door closed when showering so steam doesn’t migrate.
• Wipe windows down each morning with a microfibre cloth or a Karcher window vac (£50–£70) — removes the water before it feeds mould.

3. Keep the house evenly warm

Cold rooms condense more. Keeping the whole house at a steady 18–19°C beats blasting one room to 23°C while bedrooms sit at 14°C. A smart thermostat with room sensors helps balance this. Also check your loft insulation — warm ceilings mean less condensation on upstairs windows.

What about secondary glazing and window upgrades?

Better windows genuinely help — the inner pane stays warmer, so less condensation forms:

• Secondary glazing (£300–£500 per window) — good for period properties where double glazing isn’t allowed
• Full double glazing replacement — see double glazing costs per window

But note: new airtight windows without improved ventilation can shift condensation to the next coldest surface (often walls). Always pair window upgrades with ventilation.

Dealing with existing mould

Black mould around windows is common and fixable — see our guide on getting rid of mould permanently. In short: clean with a mould remover (not bleach — it doesn’t kill the roots on porous surfaces), fix the moisture source, and repaint with anti-mould paint.

Quick daily routine that works

1. Morning: wipe windows, open trickle vents
2. Cooking: extractor on, lids on, window cracked
3. Showering: extractor on + 15 min after, bathroom door shut
4. Laundry: dehumidifier or vented drying — never on radiators in closed rooms
5. Evening: heating steady at 18–19°C throughout

The bottom line

Condensation is a ventilation problem wearing a window costume. Open the trickle vents, run the extractors, stop drying clothes on radiators, and wipe the glass each morning — that combination solves 90% of cases for under £200 (mostly the dehumidifier). If mould is already established or condensation persists despite all this, look at PIV ventilation or window upgrades. Your lungs and your window frames will thank you.

Condensation in rentals: your rights

Renters face condensation more than anyone — and the blame game (“you’re not ventilating properly”) is exhausting. Know this: landlords must ensure the property is fit for habitation, which includes working extractor fans, adequate heating and freedom from serious damp. If the bathroom has no extractor fan, or the one fitted is useless, that’s the landlord’s problem to fix — request it in writing.

That said, tenant behaviour does matter and adjudicators know it. If you’re drying clothes on radiators in every room with the windows sealed, some responsibility is yours. The winning approach: document everything — photograph the condensation/mould, log when it appears, keep copies of your written requests to the landlord. If the landlord won’t act, your council’s environmental health team can inspect and issue improvement notices. Under Awaab’s Law (applying to social housing, with private-rented equivalents strengthening), serious damp and mould must be investigated within 14 days and repaired within set timeframes.

Condensation FAQs

Is condensation on new windows normal? Some morning misting on the room-side glass is normal in cold weather — it shows the windows are sealing well (keeping heat in). Streaming water, pooling on sills, or condensation between the panes is not normal — between-pane misting means the sealed unit has failed and needs replacing.

Do dehumidifiers really work? Yes — a decent compressor dehumidifier (£120–£200) extracts 10–20 litres a day and genuinely transforms damp-feeling homes. Running cost ~20–40p/hour. They’re the best single purchase for condensation-prone homes after fixing ventilation. Desiccant models work better in cold rooms (garages, conservatories).

Should I leave trickle vents open in winter? Yes — that’s what they’re for. The heat loss through a trickle vent is trivial compared to the moisture damage of sealing the house completely. Ventilation isn’t the enemy of warmth; uncontrolled draughts are.

Why is it worse in bedrooms? Two people breathing release ~1 litre of moisture overnight into a closed room — and bedrooms are often the coolest rooms. Crack the window or trickle vent overnight, don’t dry clothes in bedrooms, and keep the heating on low rather than off.

Can houseplants cause condensation? Marginally — a jungle of 50 plants adds measurable moisture, but normal houseplant numbers are negligible compared to cooking, showering and laundry. Don’t blame the monstera.

Related reading

Condensation often leads to mould — see getting rid of mould permanently — and the NHS guidance on damp and mould for health advice.