A few days with the heating on is all it takes for your home to dry out: your jumper crackles when you take it off, the door handle gives you a shock and the tips of your plants' leaves turn brown. Cold outdoor air holds little water and, when it's heated to 22 °C, its relative humidity easily drops below 30%. If you notice dry air in the house, here's how to humidify it with simple home remedies, when a humidifier is worth it and how to avoid going to the other extreme.
What's the right humidity level at home
In a home, a relative humidity of 40 to 60% is considered comfortable. Below 35% the air feels noticeably dry; above 60% water starts to condense on the windows and mould appears more easily in the corners. Before changing anything, get a hygrometer: it's a small expense and without one you're working blind. Place it away from radiators and windows and check the reading at different times of day.
How to humidify dry air at home without a humidifier
- Turn the thermostat down by one or two degrees. The warmer the air, the lower its relative humidity for the same amount of water vapour. Going from 23 °C to 21 °C raises the hygrometer reading by several points and usually lowers your bill too.
- Air the room briefly but thoroughly. A window left ajar all day lets in a constant stream of cold, dry air and cools the walls. It's better to open the windows wide two or three times a day for 5-10 minutes, with the radiators turned off in the meantime. Don't stop ventilating: your home needs fresh air; it's just a matter of doing it quickly.
- Dry your washing indoors. A load of washing hung up in the living room releases more than a litre of water into the air. At the height of the heating season, it's a free humidifier. Put the clothes airer in a room, not in the bathroom, and keep an eye on the hygrometer: if it goes above 60%, open a window.
- Water containers on the radiator. The ceramic or plastic humidifiers that hang on radiators do work, though modestly: they're a complement, not the solution. Change the water every few days and wash the container, because standing water quickly builds up limescale and dirt.
- A damp towel over the radiator. A quick fix for the bedroom at night. Only on water-filled radiators, never on electric, oil-filled or convector heaters. Don't cover the thermostatic valve head, or it will misread the room temperature.
- Bathwater. Don't empty the bath as soon as you've finished: let it cool down with the bathroom door open. If there are young children at home, this trick is ruled out.
- Houseplants. Plants release water through their leaves, so several large pots grouped together help a little. If you have a dog or cat, choose species considered non-toxic to them, such as the Boston fern, the spider plant or the areca palm. The peace lily, often mentioned in guides on humidity, is toxic to dogs and cats.
Humidifiers: which one to choose
If, even so, your hygrometer consistently reads below 35%, home remedies aren't enough and a humidifier is a good idea. There are three main types:
- Ultrasonic: quiet and energy-efficient. With hard tap water it leaves a fine white limescale dust on furniture, so it's best to use demineralised or filtered water.
- Evaporative: a fan draws air through a wet filter. It leaves no dust and it's hard to overdo it, because the more humid the room, the more slowly it humidifies. The filter needs replacing from time to time.
- Steam: it boils the water, so the steam comes out hot. It uses the most electricity and must be kept out of reach of children and animals.
Whatever the type, look for one with a humidistat, the function that switches it off automatically once it reaches the humidity you've set. Empty and clean the tank according to the instructions and choose the model based on the size of the room. If you have a cat, don't add essential oils to the water: many are harmful to cats and, besides, most humidifiers aren't designed for them.
Dogs and cats with the heating on
Dogs and cats love lying next to the radiator, and they feel the dry air too: their fur gets full of static and the water in their bowl evaporates faster. Check the level and top it up with fresh water often. Static-charged hair clings more to clothes and upholstery; for everyday use, a quick fix is a self-cleaning pet hair roller, and you'll find more methods in our guide on how to get pet hair off clothes.
Don't overdo it: when to stop humidifying
More isn't better. If the humidity goes above 60% and there's water on the windows in the morning, you're over-humidifying. Switch off the humidifier, open the windows and take the towels off the radiators. We explain how to deal with excess humidity in how to get rid of damp in a room.
In short
Measure the humidity, turn the thermostat down by one or two degrees, air the room briefly instead of leaving the window ajar and dry your washing indoors. If that's not enough, buy a humidifier with a humidistat and stay between 40 and 60%.