Trial: Damprid vs wardrobe heater

We trialled a Damprid and wardrobe heater to see if they can stop mould or mildew ruining your clothes.

20apr wardrobe moisture hero

Have you ever noticed that musty smell when you open the cupboard in the spare room? Or have you taken a dress off the hanger only to find it covered in fuzz?

Spending a few dollars to potentially save your clothing and linen makes a lot of sense. But is saving your spare sheets really as easy as chucking in a wardrobe heater or a moisture-sucker, like Damprid? We set up a trial to find out.

Our trial

We set up data loggers, which measure temperature and humidity, in a couple of Wellington homes in late February/early March. Each house had a data logger in the bedroom and another in the wardrobe.

To start, we let them gather data over a few days to give us a baseline and check to see if the wardrobe consistently had higher humidity than the rest of the room. It did. During our trial, the wardrobes hovered at about 20°C with 70% relative humidity (RH), and consistently stayed between six and eight percent higher than the bedrooms.

Why does mould grow in wardrobes?

Mould needs damp, humid conditions to thrive. A 2009 World Health Organization study explained that while mould can grow when relative humidity creeps above 65%, things really only kick off when it’s sustained above 75%. If you have a couple of weeks of high humidity (totally achievable over a Kiwi winter) then you’ll have mould on your hands.

That’s a problem for our trial wardrobes. Even in early autumn, the humidity is high – if the temperature drops a few degrees, we’ll get to meet Mr Mould. Without any ventilation, all that needed to happen in our trial wardrobes was for the air temperature to fall to 18°C to get above the magic 75% RH mould-growing mark. If it dropped to 14°C, we’d hit the dew point and get moisture forming on the surfaces and items within. A sizable shift in temperature probably won’t happen overnight in your wardrobe over summer but it’s certainly possible in an autumn cold snap. It’s a bit alarming to know you only need a couple of degrees’ shift in temperature before things can turn ugly.

What's the dew point?

You’ve probably seen condensation form on your cold windows while the air in your lounge feels warm and not particularly humid. That’s because as air cools, it loses its ability to hold moisture (think of the air as a damp sponge being squeezed – the amount of moisture doesn’t change, but the sponge becomes increasingly saturated). Eventually, the relative humidity climbs till you hit 100% RH. At this point moisture leaves the air and forms as water droplets – this is the “dew point”.


Homeowners and tenants alike start piling moisture-absorbing products in their trolley come winter, all in the hope it’ll stop the dreaded musty smells emanating from the nation’s wardrobes.

One prominent brand – Damprid – is available at most supermarkets and hardware stores. The product’s label certainly talks a big game, promising to “prevent mould and mildew” along with “eliminating musty odours”. For $7 at Countdown, it’s certainly a low-cost option. Each unit comes with a little basket that you fill with supplied calcium chloride crystals. The calcium chloride absorbs airborne moisture to the point where the crystals turn into liquid themselves. This is then caught in the container rather than in the air. Once everything has turned to liquid, you empty the container and put in some fresh crystals and repeat the process.

We were sceptical of the Damprid’s ability to absorb loads of moisture, so we placed one in each of our trial wardrobes to see if they managed to keep the air dry.


Relative humidity in our trial homes after using Damprid. We were pretty underwhelmed by the Damprid in both our trial houses. While they reduced the relative humidity difference between room and wardrobe by two percent – the wardrobes in our homes were still four and six percent higher than the rooms, and the RH was still sneaking into the danger zone where mould could begin to grow. After more than a week, the crystals had melted into one mega-crystal but, there was still no liquid in the bottom of the container. This showed they were working, albeit at a snail’s pace.

Cupboard heaters

Cupboard heaters have been on the scene for ages. Mounted to the wall, they quietly chug away and put out modest amounts of heat. Think of them as the wimpy sibling of your standard convection heater – they tend to have a power output of 60-100W. To put that in perspective, it’s equivalent to having an old incandescent lightbulb buzzing away all the time.

Their low wattage consequently means low power usage – they’ll use as much in 24 hours as a regular plug-in heater does in an hour. They cost in the region of $100 and, if you already have a plug in your wardrobe, you can easily install it yourself. However, most wardrobes don’t, so you’ll probably need to get a sparky to install it.

Relative humidity in house 1 after using wardrobe heater.

The cupboard heater didn’t have a drastic impact in our trial home. The humidity remained higher than in the bedroom and the temperature wasn’t elevated at all. This performance was on par with the Damprid. It was a bit disappointing, but not unexpected with such a weedy wattage.

It might’ve been unfair on the heater to do the trial at the beginning of March. It could still have a part to play over winter in preventing the really chilly temperatures where high humidity is the mainstay.


Even if the Damprid was working at a frantic pace and all the crystals were turning to liquid in a week, you’d still only extract a maximum of 500-600ml of water from the air in your cupboard. While that might make a difference in a tiny confined space that’s well sealed, if you’re opening and closing the wardrobe every day, it’ll struggle.

The cupboard heater makes a more compelling case for inclusion in your house, but you need to size it right so it isn’t underpowered for the space.

So will a piddly moisture-absorbing container or heater do the trick? If you own a well-insulated modern home, they could be helpful, but in a draughty old villa, they’ve got next to no chance. In that case, you’ll need to actively fight the damp.

One course of action you could take is buying a cheap humidity and temperature data logger and see what’s really happening in your cupboards. We were taken aback by the high humidity levels (six to eight percent higher than in the bedroom) and it really drove home the point that you need to actively manage the situation, otherwise you’ll end up needlessly chucking out ruined clothes.

What else can you do to look after your clothes?

There are a couple of sure-fire ways to help keep your wardrobe and clothes smelling fresh.

  • Leave the wardrobe door open a crack, or fit vents to the door, so it doesn’t get too stuffy in there.

  • Ensure your clothes aren’t too tightly packed so there’s sufficient airflow around garments.

  • Bung a dehumidifier in the doorway to slurp up extra airborne moisture.

  • Don’t hang damp clothes. It might help with ironing (especially dress shirts), but it’ll fill the air with moisture as they dry on the hanger.

  • Raise items off the floor and away from walls, which is where condensation can form.

Watch this space …

Our moisture-sucking trials aren’t over yet. We’ll be checking how the wardrobe heater performs in the middle of winter. We’re also going to find what happens if we chuck a dehumidifier in the cupboard. For bigger results, we’re also assessing the effects a heat pump on dry mode can have on a bedroom. Check in online to see what impacts these trials have in our wardrobes.

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