by Chris Woodford. Last updated: October 1, 2013.
Is damp climbing up your walls... and driving you up the wall? Few things make a home quite so unpleasant. Whether you have a damp problem with your building (rising or penetrating damp) or your moisture comes from cooking or drying laundry inside (condensation), the result can be a horrible musty smell, mold growing on your walls (and on your clothes), and a greater risk of respiratory illness. It can take time to sort out a major damp problem so what do you do in the meantime? One solution is to invest in a dehumidifier: an electric gadget that removes moisture from the air. Let's take a closer look at how they work!
Photo: A typical home dehumidifier. A machine like this costs about $200 (£100) and uses about 190 watts of electricity (slightly more than three ordinary 60-watt lamps burning at once), so it's reasonably economical to run. This one is a DEM10 made by DeLonghi, though many other makes and models are available.
What is humidity?
Most of the time we don't give a moment's thought to the atmosphere in our homes (or outside); why should we, it's invisible! If we think about it at all, we tend to think of it as a gas. Look up at the sky and you see a different point of view. Clouds whizzing over your head are a sure sign that the air contains water, either as a vapor (if it's dry) or liquid (if it's actually raining). But the same is true inside your home. You might think the air is dry—and if you have central heating, it might even feel that way—but there's a huge amount of moisture around you too. If you dry laundry inside your home or do a lot of stove-top cooking without proper ventilation, the humidity levels can be surprisingly high. Condensation on the windows (or, even worse, water dripping down the walls—as it sometimes does in my kitchen) is a sure sign of a humidity problem.
Why does indoor humidity matter?
We're walking water bags—our bodies are typically 60 percent water—but that doesn't mean our homes should be like fish tanks! High humidity can cause all kinds of problems. It can make clothing go moldy in your cupboard, it's bad for computers (it can cause rusting or short circuits inside their cases) and optical equipment (that's why things like cameras and binoculars are sold with water-absorbing sachets of silica gel)—and it's bad for your health too. According to a scientific review of the health effects of humidity published in 1986 by Arundel et al, high levels of indoor humidity can encourage a flourishing of bacteria, viruses, mites and fungi, and more respiratory infections and sicknesses: "The majority of adverse health effects caused by relative humidity would be minimized by maintaining indoor levels between 40 and 60%."
Photo: Water-absorbing silica gel, often packaged in little paper bags inside camera and binocular cases, effectively tackles small amounts of humidity. But it's no help if you have a major excess of moisture in your home. For that, you need a proper dehumidifier.
What does a dehumidifier do?
A dehumidifier is a bit like a vacuum cleaner: it sucks in air from your room at one end, takes the moisture out of it, and then blows it back out into the room again. The moisture drips through into a collection tank that you have to empty, from time to time. How is the moisture removed? That's where a dehumidifier is more like an air conditioning unit (sometimes called an air-con or HVAC, which stands for heating ventilating air conditioning unit), which, itself, works a bit like a refrigerator! Confused by all these appliances? Let's look inside a dehumidifier and find out what all the bits do.