The old tea towel trick that stops condensation on windows overnight and cuts mould risk dramatically

A simple cloth from your kitchen drawer can change the way your windows handle winter. While dehumidifiers and new glazing grab the headlines, many households are leaning on a cheaper, quieter ally at night: an old cotton tea towel.

Used the right way, that thin layer of fabric can soak up overnight moisture before it pools on your sills, feeds black mould, or drips behind furniture. It is not glamorous, but it is effective when you understand what condensation is really doing to your glass.

Why your windows drip while you sleep

Condensation is warm, moist indoor air meeting a cold surface. The air in your bedroom, living room, or kitchen always holds some water vapour from breathing, showers, kettles and drying clothes. When it hits cold glass, the vapour turns back to water and clings to the pane.

Modern double glazing slows heat loss, but it does not stop this process when rooms are poorly ventilated. At night, radiators cycle off, curtains close and air stops moving. The glass cools, the moisture settles and tiny droplets join into runs. Those runs collect on the frame and in the corners where mould loves to start.

Condensation you can see on the glass today often becomes mould you only notice on the sealant or wall in a few weeks.

What the tea towel trick actually does

The tea towel method is not magic. It turns your window into a controlled drying rack instead of a cold trap. Rather than letting water drip down and sit in the frame, you give it somewhere else to go and a fabric that can breathe it back out later.

A cotton tea towel acts as a sacrificial layer. The fibres catch the first fine film of water and wick it along their length. That spreading lowers the height of droplets and keeps water from pooling in one spot. It also buys you time in the morning to ventilate and dry surfaces before mould spores wake up and feed.

The visible effect is simple. You wake up to a slightly damp towel and glass that is misty but not streaming. Your frame, sill and plaster are spared the worst.

How to set it up at home

The basic overnight set‑up

You do not need tools or specialist kit. You need dry towels, a way to support them and a small habit before bed.

• Choose clean, absorbent cotton or linen tea towels. Avoid fluffy microfibre; it can stick to wet seals.
• Open your curtains or blinds fully so air can move around the glass.
• Fold the towel lengthways into a loose strip and drape the lower edge along the bottom of the inside pane, just touching the glass.
• Let the majority of the towel hang down the wall or over the radiator, not bunched on the sill.
• For tall panes or patio doors, use two towels with a slight overlap in the middle.

The most effective set‑ups keep part of the towel in contact with the glass and part hanging freely so moisture can travel and evaporate rather than just sit and soak.

Getting the height and contact right

You are aiming for light, even contact with the coldest section of glass. Pressing too hard simply pins damp fabric against the pane. Too loose and the towel never meets the condensate.

In practice, that means tucking one edge gently into the window bead or behind the trickle vent, or using a small, removable hook on the frame to catch a corner. If you have deep sills, slide a light book or a coaster under the hanging end so air can move all around the towel. This encourages it to dry as it works.

On tilt‑and‑turn or inward‑opening windows, keep the hinge side clear. You want to be able to open the window in the morning without dragging a wet towel across the plaster.

When this trick helps most

The tea towel trick shines in specific situations rather than all day, every day.

• Bedrooms where windows stream by morning despite the door being closed.
• North‑facing rooms that never quite warm up and often smell musty.
• Rental flats where you cannot fit trickle vents or a permanent ventilator.
• Short, sharp cold snaps where the glazing becomes noticeably colder than the room.

Use it on the worst‑affected panes for a week and watch the difference on your sills and silicone. Combine it with a ten‑minute morning window‑open routine, and you cut both visible moisture and the hidden damp in the frame junctions.

In very wet homes, the towel becomes an early warning. If it is soaked through by breakfast, the underlying humidity is high enough that you should review drying habits, extractor fans and furniture placement as well.

What you can realistically expect

A tea towel will not fix a leaking gutter, a broken seal or chronic rising damp. It does three modest but important things: it limits how much water can pool on your frames, it slows down mould growth, and it makes daily moisture visible so you can act.

You can expect:

• Less standing water at the bottom of panes.
• Fewer black specks forming around the silicone and beading.
• Reduced musty odour near heavy curtains and in window bays.

You should not expect bone‑dry glass every morning or a replacement for good ventilation. Think of the towel as a night‑shift helper for rooms where dehumidifiers are too loud, too costly to run, or simply impractical.

Do not confuse moisture management with structural repair. Ventilation, heating balance and fixing leaks always come first.

Risks, limits and how to avoid problems

Used badly, any fabric near a cold, damp surface can create its own issues. A few simple rules keep the trick safe and useful.

• Do not leave the same towel up day after day. Rotate and dry them fully between uses.
• Avoid letting towel edges sit permanently against painted timber; long‑term damp contact can soften paint.
• Keep towels clear of plug sockets, curtain tie‑backs and nearby lamps.
• If you have mould allergies or asthma, handle very damp towels with gloves and wash them hot.

In homes with timber frames or original sashes, keep an eye on putty and paintwork. If you notice softening or discolouration, reduce the contact area and focus on shorter overnight periods with more morning air changes instead.

How it compares with other simple options

You can blend the tea towel method with other low‑cost condensation controls. Each does a slightly different job.

Method	What it does	Best use
Tea towel on glass	Soaks fresh condensate	Night‑time, quiet rooms
Night‑vent window gap	Lets moist air escape	Mild or breezy nights
Portable dehumidifier	Extracts water from air	Very damp rooms, laundry days

The towel method is the easiest to start with because it costs nothing if you already own spare cloths. Use it as a test. If a single towel is saturated most mornings, you have a humidity load that will benefit from adding one of the other measures.

Small habits that boost the effect

The towel trick works best as part of a small nightly routine that stops moisture building faster than you can catch it.

• Shut bathroom doors and run the extractor during and after showers.
• Avoid drying clothes on radiators in the rooms with the worst windows.
• Pull furniture a few centimetres away from outside walls so air can circulate.
• Open bedroom windows for 5–10 minutes after you get up, even in winter.

Those habits do not need to be perfect every day. They simply lower the background moisture so the towel spends its time catching the last bit of condensate, not fighting a fog.

A repeatable plan for clearer panes and less mould

Pick the window that suffers most. Put a dry tea towel in place before bed for three consecutive nights. Each morning, check:

• How damp the towel feels along its top edge.
• Whether your sill, frame corners and wall edges are wet or just cool.
• Any change in smell or visible hazing around the silicone line.

If you see less pooling and cleaner frames, expand the method to the next worst window and add a short morning airing. If nothing changes, you have likely reached the point where fabric alone is not enough, and it is worth looking at ventilation upgrades or a small dehumidifier.

FAQ:

• Will this work with double‑glazed windows that already have trickle vents? Yes. Trickle vents help exchange air, but they do not catch the condensate that still forms on cold nights. A towel simply reduces what reaches the frame.
• Can I leave the towel touching the glass all day? It is better to remove it in the morning, dry it elsewhere and let the frame and glass return to room temperature. Constant damp contact is not ideal for any surface.
• How often should I wash the towels? Weekly is fine in most homes. In very damp properties, wash more often to prevent musty smells and to stop mould spores building up in the fibres.
• Will this stop mould that is already there? No. It slows new growth by removing fresh moisture, but existing mould needs to be cleaned safely and, in bad cases, assessed by a professional.
• Is kitchen roll or newspaper a good substitute? They can blot up water in an emergency, but they tear easily and can leave ink or fibres behind. Reusable tea towels are more robust and kinder to frames.