Canadian Woodworking

HomeInOn – dehumidifiers

Author: Carl Duguay
Photos: Frigidaire
Published: August September 2019

Excessive humidity can be a real problem for your home and your health. We look at how a dehumidifier can help get things back under control.


A dehumidifier is an often-overlooked part of the home, yet it can deal with many humidity problems. Humidity is moisture, in the form of water vapour, in the air – there can be too much of it, not enough of it, or it can be just right. It’s measured on a scale that goes from 0 (bone dry) to 100 percent (sogging wet). In very simple terms, the relative humidity level is a measure of how much water vapour the air can hold (at a specific temperature). We instinctively know there is too much moisture in our homes when we see beads of water condensing on windows; mold growing on the walls, floors, window sills, or around bathroom fixtures; water stains appearing on walls or ceilings; or musty odours wafting through the basement or laundry room. Left unattended over a period of years, these issues can cause structural problems in the home and various health issues, including an onset or exacerbation of allergic symptoms and skin conditions such as eczema. If you don’t have one, consider a dehumidifier for your home this summer.

Most of the studies I looked at say the ideal indoor humidity level should be somewhere between about 30 and 60 percent – the comfort zone. Relative humidity beyond about 70 percent creates the perfect breeding ground for mold, mites and fungus. Under 30 percent, and you’ll probably start to develop dry skin, itchy eyes, irritated sinus and throat, and the disconcerting ‘frizzy’ hair look.

How Humid is It?
A hygrometer is a simple and cost effective way to monitor how humid your home is.

Easy to Understand
 For the most part dehumidifiers are fairly simple to operate. Basic settings such as humidity level, a timer and fan speed are common.

Tank Size
Some tanks are quite large, while others are small. Unless you plan on hooking your dehumidifier up to a drain, consider how large an area the dehumidifier will be working in, and how humid the area traditionally gets.

Direct Hookup
 Many dehumidifiers will allow you to attach a hose to them, so that the unit will empty into a drain. This is especially helpful if you're out of the house all day, or the humidity levels in your home are high.

Air Filters
 Not all dehumidifiers are the same. It's best to select a model with an air filter that's easily accessed and cleaned. (Photo by Carl Duguay)

Exactly how humid?

If you don’t want to rely on your eyes and nose for confirmation that there is a humidity problem in your home you could purchase a hygrometer, which will provide a relative humidity reading, typically in the 20- to 90-percent range. They run from about $10 (with an accuracy of about +/- 10 percent), to over $100 (with an accuracy of +/- 1 percent).

While you can experience high humidity levels anywhere in your home, the most likely locations are in the basement, laundry rooms, bathrooms, and unheated and/or uninsulated rooms.

Causes include inadequate air venting to the outside, moisture seeping into your home (for example through cracks in the basement, damaged flashing around the chimney, plumbing vents or windows, broken or backed up gutters and downpipes), or from damaged ground and surface drainage around a foundation. Attending to these types of issues will deal with the problem at the source.

An effective way to reduce high levels of humidity in your home is with a dehumidifier. They use a fan to draw humid air across coils that are filled with a refrigerant. The coils cool the air, and moisture then condenses and drips into a discharge water tank, while dry air is vented out into the room.

Select the appropriate size for the space to dehumidify

Dehumidifiers are rated on the amount of moisture (measured in pints) they can remove over a 24-hour period. There are models available in the 30- to 90-pint capacities. A 70-pint model then, will remove 70 pints of moisture over 24 hours. The dehumidifier you will need for a specific room depends on the size of the room (in cubic feet) and the typical humidity level of the room (which you can obtain from a hygrometer). Then consult a manufacturer’s dehumidifier sizing chart to help you make the right choice.

Power draw is important for 24/7 operation

The power draw for most dehumidifiers will be listed at maximum humidity (100 percent). For a 70-pint model this will be about 700 watts. However, the humidity level in any home will likely never reach 100 percent, so the power draw will be lower.  If the humidity level is around 70 percent, and the power draw is in the 600-watt range, then the cost to operate the dehumidifier for 24 hours will be around $1.50, or $45 a month (assuming 10.5 cents per kWh). You’ll save money if the dehumidifier has an auto shut-off feature that turns off the compressor when the desired level of moisture has been removed from the air and turns it back on when the humidity level goes above the desired setting. Others have timers that run the dehumidifier for specific periods of time, typically up to 24 hours in half-hour increments. In any event, consider buying a model like the Frigidaire FFAD7033R1, that has an Energy Star rating.

Check hygrometer accuracy

Dehumidifiers use an internal hygrometer to measure the relative humidity in the surrounding air, and usually display the humidity in 1 percent or 5 percent increments. For greater accuracy, choose a model that measures and displays humidity levels in the smallest increments.

Consider a low decibel model

Noise output will be important if you place the dehumidifier in or adjacent to a continuously used living space. Normal conversation is about 60 decibels – dehumidifiers can easily exceed that level, particularly at high fan speeds. Remember too that manufacturers often list the decibel level at 10 feet from the dehumidifier – the sound level can be appreciably higher adjacent to the unit. If the air intake is located on the back of the unit, you’ll need to position it at least a foot from the wall to ensure adequate air circulation; if air is pulled in through the front of the unit and expelled through the top or side, you can position it right up against the wall.

Water discharge tanks need continual emptying

The discharge tanks on dehumidifiers aren’t very large – about 15 pints for a 70-pint model, and as low as 7 pints for a 30-pint model. So if you were to run that 70-pint dehumidifier 24/7, you might have to empty the tank 4 or 5 times a day. Fortunately almost all models will automatically turn off when the tank is full. Most also enable you to discharge the water through a hose into a drain, which is ideal if the unit is located in the basement or laundry room.

Other features of note

The air intake filter needs to be regularly cleaned. Select a unit with a filter that is washable and easy to remove and reinstall. If you plan to use the dehumidifier in various locations around the home, caster wheels, and possibly a retractable handle, will be convenient. Also convenient is an LED display panel that shows the ambient room temperature. One-year warranties are typical, though some manufacturers offer a full 2-year warranty. Some also offer an extended warranty on the compressor, evaporator and condenser.


Carl Duguay - [email protected]

Carl is a Victoria-based furniture maker and the web editor at Canadian Woodworking & Home Improvement.


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  2. Could you recommend a dehumidifier that last more than one or two years?
    My last 3 dehumidifier didn’t last long and I don’t know if it is worth to repair them or just buy a new one.

    1. Unfortunately all the dehumidifiers I looked at have a 1 year warranty. Still, you should be getting at least 5 years of service on a top rated model. Some manufacturers offer extended warranties that aren’t overly expensive so are worth considering.

  3. I think you did a good job of covering most of the important aspects of choosing a dehumidifier for home use. However, there are two things you did not mention that are worth noting.

    First, home-use dehumidifiers work by blowing room air over a chilled coil to condense moisture out of the air. When used in an environment below about 20 degrees C (67 degrees F), such as cool basements, frost and ice start to form on the cold coils. The frost and ice on the coils greatly reduces the effectiveness of a dehumidifier to the point that the dehumidifier does little but make noise, add heat and consume electricity.

    The second thing worth pointing out is that, like refrigerators, dehumidifiers give off heat. If used in smaller spaces they can considerably add heat to that space. If one intends to use a dehumidifier in a very small space, one should probably purchase a dehumidifier that has thermal protection, turning off if it overheats. (I’ve burned out more than one dehumidifier in elevated temperatures in small spaces, such as a large closet.)

  4. Thanks for the info. A hygrometer is a valuable tool for gauging the humidity in a room. From my experience, dehumidifiers are notoriously inaccurate so a digital hygrometer will give you a truer reading. On the West Coast, I find that humidity levels are more likely to be higher in winter with closed air-tight windows.

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