Damp, Condensation and Mould? Here's What's Really Causing It
You wipe the bedroom window every morning and it is wet again by lunchtime. There is a smell in the back room that never quite goes away. The washing has been on the airer for three days and it still feels cold and damp to the touch. And then you spot it, that first dark bloom of mould creeping along the edge of the window frame.
This is not a cleaning problem. It is a moisture problem, and no amount of scrubbing will fix it. The good news is that the cause is simple, and so is the solution.
Did you know? A single load of washing dried indoors can release around two litres of water into the air of your home. Add cooking, showering and breathing, and a typical family puts several litres of moisture into the air every single day.
The Problem: Why UK Homes Get Damp
Warm air holds moisture. Cold air cannot. So when the warm, humid air inside your home touches a cold surface, a window, an outside wall, the back of a wardrobe, the moisture condenses out as water.
In British homes this happens constantly, for reasons that are hard to avoid:
- Drying laundry indoors - unavoidable for most of the year, and the single biggest source of indoor moisture
- Cooking and showering - steam that has nowhere to go once the extractor fan is off
- Modern insulation and double glazing - excellent at keeping heat in, and equally good at keeping moisture in
- Cold outside walls - the perfect surface for condensation to form on, especially behind furniture
- Keeping windows shut in winter - understandable, but it traps the damp air inside with you
Left alone, that trapped moisture creates the conditions that black mould and dust mites need to thrive. It marks your walls, ruins clothes stored in wardrobes, and leaves the whole house feeling cold and musty no matter how high you turn the heating.
The Solution: Take the Moisture Out of the Air
You cannot stop cooking, showering or washing your clothes. But you can remove the moisture those things put into the air, before it has a chance to settle on your walls.
That is exactly what a dehumidifier does. It draws in damp air, cools it so the moisture condenses out into a tank, and returns dry air to the room. Bring the humidity in a room down to a comfortable level, usually somewhere around 50 percent, and the change is quick and obvious:
- Condensation stops forming on the windows
- The musty smell fades within days
- Mould loses the damp it needs to grow
- Washing dries in hours instead of days
- The room feels warmer, because dry air is easier and cheaper to heat than damp air
What to Look For in a Dehumidifier
Not every dehumidifier is worth having. These are the features that make the real difference, and the ones both Nyxi smart models are built around:
20L or 30L? Which Size Do You Need
The only real decision is size. Here is the simple way to choose:
Choose the 20L
For bedrooms, home offices, flats, nurseries and average sized living rooms. Anything up to around 30 square metres. It removes up to 20 litres a day, moves 195 cubic metres of air an hour, and draws just 320 watts, roughly 8p an hour to run.
Choose the 30L
For open plan living spaces, larger lounges, basements, converted lofts, or a home with a persistent damp problem. Rooms up to around 50 square metres. It removes up to 30 litres a day, runs at a quiet 42 decibels, and draws 480 watts, roughly 12p an hour.
A useful rule of thumb: size for the worst room in your house, not the average one. A dehumidifier working comfortably within its range is quieter, cheaper to run and lasts longer than one running flat out at its limit. And since both models roll on castors, you can always wheel it into the utility room on laundry day.
Side by Side
| Nyxi 20L Smart | Nyxi 30L Smart | |
|---|---|---|
| Extraction | 20L per day | 30L per day |
| Room size | Up to 30m² | Up to 50m² |
| Airflow | 195 m³/h | 150 m³/h |
| Power | 320W (about 8p/hour) | 480W (about 12p/hour) |
| Water tank | 6.5L | 6.5L |
| Dimensions | 34 x 24 x 57cm | 37 x 21 x 60.5cm |
| Wifi, Alexa, Google | Yes | Yes |
| Laundry drying | Yes | Yes |
| Carbon filter | Yes | Yes |
Shop the Nyxi Smart Dehumidifiers
Wifi app control, Alexa and Google Home, a 6.5 litre tank and laundry drying mode as standard on both models.
Getting the Most From Your Dehumidifier
- Close the doors and windows in the room you are treating. A dehumidifier cannot win against an open window.
- Aim for around 50 percent humidity. Lower is not better, and over drying a room just wastes electricity.
- Give it space to breathe. Leave a gap around the unit so air can circulate through the intake and outlet.
- Clean the filter regularly. A blocked filter makes the unit work harder for less result.
- Use laundry mode with the door shut. You will be surprised how quickly a full airer dries.
Dehumidifier FAQs
Will a dehumidifier get rid of mould?
A dehumidifier removes the damp that mould needs to grow, which stops it coming back. You will still need to clean off any mould that has already formed, but once the humidity is under control it should not return.
How much does a dehumidifier cost to run?
The Nyxi 20L draws 320 watts, about 8p an hour, and the 30L draws 480 watts, about 12p an hour. For comparison, a tumble dryer typically costs between 52p and 78p an hour, which is why drying laundry with a dehumidifier is so much cheaper.
Can I leave it running all night?
Yes. Both models have a sleep mode and a 24 hour timer, and the 30L runs at a quiet 42 decibels. The tank shuts the unit off automatically when it is full, so it is safe to leave unattended.
Where should I put it?
In the room with the worst damp, with the doors and windows closed. Leave a gap around the unit for airflow. Both models have castors, so you can move it wherever it is needed.
Do I have to keep emptying the tank?
Both models have a generous 6.5 litre tank, larger than most, so it needs emptying less often. If you would rather not empty it at all, connect the included 60cm drain hose and let it drain away continuously.
Does it really work with Alexa and Google Home?
Yes. Both models connect to the Nyxi app over wifi, and the app links to Amazon Alexa and Google Home, so you can control the unit through a smart speaker you already own.
Running costs are estimates based on an electricity price of 26p per kWh and will vary with your tariff and how long the unit runs. Extraction rates are quoted at 30°C and 80% relative humidity, the standard test conditions for this class of appliance. Real world extraction is lower in a cooler, less humid room.
