Why your indoor air might be drier than the Sahara this January – and the wet towel fix that costs nothing

Your lips crack, your throat feels scratchy, the washing dries in an hour flat – and yet the windows don’t mist like they used to. That’s the quiet twist of a modern British winter. We’ve sealed our homes, cranked the radiators, and in the process turned the living room into a pocket desert.

On a cold night in January, the Met Office might tell you the relative humidity in your town is 80%. Step into a centrally heated flat and it can plunge below 25%. The Sahara often sits around 25% too. You’re standing in a warm room that’s technically as dry as a desert, then wondering why your skin protests.

A kettle hisses, the boiler clicks on, and your nose starts to sting. Sound familiar? That’s not just “winter”. That’s physics, insulation, and our heating habits teaming up.

Why heated air feels like desert air

When we heat air, we don’t magically add water to it. We simply make the same amount of moisture stretch over a bigger volume. Warm air can hold more water vapour than cold air, so the relative humidity drops when you switch the heating on. It’s like taking a teaspoon of cordial meant for a tumbler and tipping it into a jug.

Dry outdoor air worsens it. High‑pressure winter systems pull in cold continental air that already holds very little moisture. We warm that up indoors, the thermostat reaches 20–22°C, and suddenly our skin and sinuses become the nearest source of water. Your body does the topping up.

You can measure it if you like. A cheap digital hygrometer in a typical UK sitting room in January will often read 20–35% once the radiators have been on for a few hours. Comfort for most people starts around 40–50%. Below that, static shocks and sore throats appear. Above 60%, you’re in condensation and mould territory. We’ve simply overshot on the dry side.

The quiet costs of desert‑dry rooms

Dry air doesn’t just feel unpleasant; it changes how your home and body behave. Mucous membranes in your nose and throat lose moisture faster, so their natural barrier function drops. That’s one reason winter colds spread easily in heated buildings, even when it’s damp outside.

Timber floors and furniture shrink and creak. Houseplants crisp at the edges no matter how dutifully you water them, because the leaves are losing moisture to the air faster than the roots can keep pace. Waking up with a sticky tongue and a dull headache becomes normal. You tell yourself you just slept badly.

There’s a money angle too. Very dry air doesn’t actually make your room colder, but it often feels harsher. People respond by nudging the thermostat up a degree or two. For a typical UK gas‑heated home, that can add 5–10% to your bill across the cold months. Not huge in a single week, but enough to matter over a winter.

The wet towel trick: how to add humidity for free

Here’s where one of the simplest winter habits quietly earns its place: the wet towel on the radiator. You’re already paying to heat that metal panel. You might as well use the same energy to nudge the moisture back up.

The method is almost insultingly simple. After a shower, instead of spinning your towel bone‑dry or draping it where it barely warms, wring it out lightly and lay it flat over a hot radiator or airer in the room you actually live in. As it warms, water evaporates slowly, lifting indoor humidity by a few percentage points over the next hour or two. No gadgets, no cartridges, no refills.

You can do the same with a thin cotton sheet, an old pillowcase, or a tea towel. The goal isn’t to turn your house into a steamy laundry; it’s to trade a little of that wasted dryness for comfort. One towel won’t fix a whole house, but it can transform the sofa corner where you spend your evening.

You’ve paid once to heat the water in your heating system. Let it work twice: warmth for your body, moisture for your air.

How to use the wet towel fix without turning the place clammy

A few tweaks make this almost foolproof:

• Pick thin, fast‑drying fabrics rather than a huge, dense bath sheet.
• Aim for lightly damp, not dripping. If water runs onto the floor, it’s too wet.
• Keep it to one or two radiators at a time, ideally in the rooms you actually use.
• Avoid draping towels on electric panel heaters or convectors unless the manual says it’s safe.

If your windows start to bead with water, you’ve gone too far. Crack them for two minutes after the heating switches off and the excess moisture will leave without stripping all the warmth. Think of it as trimming a sail, not opening the harbour gate.

Why this costs (almost) nothing

The beauty of the wet towel trick is that it doesn’t ask your boiler for anything extra. The heat is already flowing through the radiator. Whether that panel warms bare air or a damp towel first, the boiler output is essentially the same. The only real “cost” is that evaporating water can make the radiator feel slightly cooler to the touch, so it may run a little longer to reach your thermostat setting.

In practice, you’re rarely forcing the system to work much harder. You’re shifting when and where the moisture enters the air, not inventing it from nowhere. Many homes are already drying washing indoors on racks; this is just a more controlled, smaller‑scale version that focuses on one room for comfort rather than turning the house into a steam tent.

Leftover heat is underrated. Your heating cycle overshoots a little, walls and furniture soak warmth, and the room stays toasty after the boiler cuts out. Allowing a damp towel to sip some of that warmth on the way through is simply a way to get a second “service” from the same unit of energy.

A simple routine that actually fits a busy day

The trick works best when it rides along with what you’re doing anyway. Try this rhythm:

• Morning – After your shower, hang the used towel on a bedroom or hallway radiator while you get ready. It will add a gentle lift of moisture while everyone’s rushing about.
• Evening – After washing up, dampen a clean tea towel or small cloth and place it on the radiator in the room where you’ll watch TV or read. Remove it once it feels mostly dry.

That’s it. No daily chore, no new gadget to remember. Just a slight rerouting of what you already wash and dry. Let’s be honest: nobody is going to hover over a humidifier gauge every night in January. But slinging a towel over a radiator as you walk past is entirely believable.

When to stop – and what not to do

There is such a thing as too much of a good thing. If you struggle with condensation, black mould, or single‑glazed windows that stream in the morning, you need to go gently. The goal is to bump desert‑dry rooms up into a comfortable band, not to recreate a swimming pool changing room.

Avoid these common missteps:

• Do not hang multiple dripping towels in every room.
• Do not block thermostatic radiator valves with thick layers of fabric.
• Do not use this method in rooms that already have moisture problems, like unventilated bathrooms.
• Do not rely on this as a cure for all winter ills; it’s a comfort tweak, not a building fix.

If you’re renting and fighting mould, prioritise short, sharp ventilation bursts and keeping furniture away from cold external walls. The towel trick belongs mainly in better‑insulated, overly dry spaces: newer builds, well‑sealed flats, or any room where your hygrometer sulks below 35%.

A tiny habit, not a home‑improvement project

Like baking on a Sunday to warm the kitchen or simmering herbs to freshen a room, this is less a hack and more a habit. You’re pairing something you must do anyway – wash towels, dry clothes, take showers – with a small atmospheric nudge that makes winter more liveable.

The win is modest but real. Fewer nosebleeds. Hands that crack a bit less. A living room that feels cosy at 19°C instead of demanding 21°C. Those changes won’t show up as a banner on your smart meter, but your body will notice.

You don’t need to turn humidity into a hobby. A single £5 hygrometer on a bookshelf and a couple of well‑timed towels in January will tell you most of what you need to know. You’re aiming for a room that doesn’t bite your throat when you breathe in, where the air feels soft rather than sharp. Not a jungle. Just not the Sahara either.

Key point	What it means	Why it helps you
Heated rooms run desert‑dry	Central heating drops indoor relative humidity far below outdoors	Explains itchy skin, sore throats, and static shocks in winter
Use heat twice	Let radiators dry lightly damp towels in lived‑in rooms	Adds gentle humidity without buying a humidifier
Aim for balance	Target 40–50% humidity, avoid streaming windows	Keeps you comfortable without feeding mould

FAQ:

• Is hanging a wet towel on the radiator safe? For standard hot‑water radiators, yes, as long as the towel is just damp and not covering any electrical parts or thermostatic heads. Check the manual for electric heaters, as some are not designed to be covered.
  
• Will this make my home damp or mouldy? Used moderately in already dry rooms, it’s unlikely. If you see persistent condensation on windows or walls, reduce how much you’re adding and ventilate briefly after the heating goes off.
  
• How do I know if my air is “too dry”? A hygrometer reading under roughly 35% is a good clue, as are recurring dry eyes, sore throat on waking, and cracking wooden furniture. Above 60% for long periods, damp becomes the bigger risk.
  
• Is a proper humidifier better than towels? A dedicated humidifier gives more control and can serve larger spaces, but it uses extra electricity and needs cleaning. Towels are a free, low‑effort experiment to see if humidity is even your issue.
  
• Can I do this in a child’s bedroom? Yes, with care. Use a small, thin towel on a safe radiator, keep it out of reach, and avoid overdoing it. If the room feels stuffy or the windows mist heavily, scale back and ventilate briefly each day.