Dehumidifiers use a heat pump (similar to an air conditioner's heat pump) or chemical adsorbents to remove 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 almost 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 into the air. It returns to the indoor air the heat generated by the dehumidifier turning water vapour to liquid.
Chemical adsorbent dehumidifiers
This type of dehumidifier is designed for hot, humid climates and is not really suited for use in Canada.
Chemical adsorbent dehumidifiers absorb moisture from the air with a "desiccant"--a drying agent such as silica gel. The desiccant is on a heat exchange wheel. A separate air loop dries the wheel and exhausts the warm, moist outdoor air through special pipes.
A chemical absorbent dehumidifier uses more energy than a heat pump dehumidifier. And 'only convenient if you use natural gas for heat exchange - and only then, when natural gas is available for a low rate of summer.
Homemade Dehumidifiers
Some inventive people use bags of road de-icing salts absorb moisture from the air. The saline wet drips in a bucket or floor, air-drying. Because the salt runs with theThe water is removed from the sky, must be replaced. The system has no moving parts.
If you try this at home dehumidifier, remember that salt is highly corrosive to metals and quite hard on the skin.
Dehumidifying ventilators
This type of dehumidifier has a sensor control and extraction. Insert the sensor control will run when humidity reaches a certain level. A dehumidifying ventilator is particularly effective when the source of moisture is in the basement.
Dehydrationventilators don't recover heat but they use less electricity than heat pump dehumidifiers. They are not effective in hot, muggy weather, as they bring more outside air into the house. They can be effective in cold weather.
A dehumidifying ventilator depressurizes your basement, which can cause combustion gas spillage. Make sure your heating contractor checks the venting for your gas furnace, water heater and wood-burning appliances. Consider using a carbon monoxide warning device if 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 seems to be the best time to buy: in the last few years dealers have held sales early in the spring with savings of to 0.
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 0 and 0 for a unit rated at 10 L (21 U.S. pints or 2.1 imperial gal.) a day--suitable for a small house with a moderate moisture problem. The price rises to between 0 and 0 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 if they both have the same Efficiency Factor. The next section explains the Efficiency Factor.
Don't try to save money by buying a unit that does not have automatic defrost. If a room is too cool, a dehumidifier can frost over and stop removing moisture. A frosted-over dehumidifier left running for a long time 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.
