Dehumidifiers use a heat pump (much like an air conditioner's heat pump) or chemical adsorbents to eliminate moisture from the air without cooling the air.

A heat pump dehumidifier uses a fan to draw indoor air over a heat exchange coil. The coil is nearly freezing. The water in the air condenses on the coil and is drained. A second heat exchange coil reheats the air, which the dehumidifier exhausts into the room.

A heat pump dehumidifier dumps heat lost from the compressor and fan motors in to the air. It returns to the indoor air heat generated by the dehumidifier turning water vapour to liquid.

Chemical adsorbent dehumidifiers

This sort of dehumidifier is designed for hot, humid climates and is not actually suited for used in Canada.

Chemical adsorbent dehumidifiers absorb moisture from the air with a "desiccant"--a drying agent such as for example silica gel. The desiccant is on a heat exchange wheel. A separate air loop dries the wheel and exhausts the hot, damp air outdoors through special ducting.

A chemical adsorbent dehumidifier uses more energy when compared to a heat pump dehumidifier. It is only cost-effective when it uses natural gas for heat exchange--and then only if natural gas is available at a low summer rate.

Homemade dehumidifier

Some inventive people use bags of road de-icing salt to absorb moisture from the air. The wet salt solution drips into a pan or floor drain, drying the air. As the salt runs off with the water taken off the air, it must be replaced. The system has no moving parts.

If you try out this homemade dehumidifier, understand that salt is highly corrosive to metals and quite hard on the skin.

Dehumidifying ventilators

This kind of dehumidifier includes a sensor-controller and exhaust fan. You set the sensor-controller to perform when humidity reaches a collection level. A dehumidifying ventilator is particularly effective if the humidity source is in your basement.

Dehumidifying ventilators don't recover heat but they use less electricity than heat pump dehumidifiers. They're not effective in hot, muggy weather, because they bring more outside air in to the house. They might be effective in winter.

A dehumidifying ventilator depressurizes your basement, which can cause combustion gas spillage. Make sure your heating contractor checks the venting for the gas furnace, water heater and wood-burning appliances. Contemplate using a carbon monoxide warning device in the event that you install a dehumidifying ventilator.

Choosing a Dehumidifier


Dehumidifier purchase costs

Heat pump dehumidifiers are complex, low-production machines and are not low-cost items. Spring appears to be the best time to get: in the last few years dealers have held sales early in the spring with savings of $50 to $100.

The more water a dehumidifier holds --which is measured in litres or U.S. pints a day--the more it costs. You pay more for special features.

In 2000, you can expect to pay between $200 and $250 for a unit rated at 10 L (21 U.S. pints or 2.1 imperial gal.) a day--suitable for a small home with a moderate moisture problem. The price rises to between $250 and $350 for a unit with a capacity of 20 L (42 U.S. pints or 4.3 imperial gal.) a day--suitable for a large house with more severe problems.

Running costs for both units are about the same should they both have exactly the same Efficiency Factor. Another section explains the Efficiency Factor.

View website try to save money by buying a unit that will not have automatic defrost. In case a room is too cool, a dehumidifier can frost over and prevent removing moisture. A frosted-over dehumidifier left running for years will break down.

Get a unit with a two-speed fan. They are quieter at lower humidity, which reduces the nuisance factor. Test all units in the store for noise level, especially if you plan to use one in or near a bedroom.