Use of a dehumidifier is recommended if the relative humidity in a room tends to remain above 60% in summer, or above the normal range (between 30% and 55%) in winter. Excess moisture in a home’s indoor air can lead to health problems for its occupants, and can also harm the building itself (stained surfaces, appearance of mould, etc.). By keeping the air dry, you can prevent all kinds of issues.

Choosing a portable dehumidifier

Dehumidifiers sell for between $200 and $400 depending on capacity and features (Protégez-vous magazine tested several models in 2017). Dehumidifier capacity is measured in U.S. pints or litres of water removed per day (one pint is roughly equal to half a litre). The most commonly sold units, e.g., those designed for basements, have a daily moisture removal capacity of between 20 and 25 litres.

The better models are Energy Star rated. You’ll also appreciate the following features:

  • Control buttons and an electronic hygrometer;
  • An automatic shutoff system to prevent overflow;
  • A drainage system.

To avoid the hassle of emptying the tank all the time, choose a unit with a rear drain port so you can connect a hose to direct the collected water to a floor drain.

How a dehumidifier works

Like an air conditioner, a dehumidifier consists of a fan and a compressor connected to two coils (one for cooling and one for warming) filled with liquid coolant.

The fan draws the surrounding air into the dehumidifier and across the cooling coil, which lowers its temperature and pulls moisture from it. The resulting water droplets (the condensate) drip into a collection tank. The dehumidified air then flows past the warming coil, returning it to its original temperature by recovering the heat given off by the compressor, the fan motor and the refrigeration process. Lastly, the same fan that drew the moist air in blows warm, dry air back into the room.

Tips for use

Your dehumidifier will operate optimally if you follow this advice:

  • Clean the filters periodically (every two weeks to begin with, then as needed), and vacuum the coils at least twice a year, ideally in the spring and fall.
  • Close all windows in the room to limit intake of outside air, especially when the humidex is high or when it rains.

If you don’t want to be bothered by noise from the unit, position it away from leisure areas. The laundry room is often the perfect place.