FAQ About Air Fans

Frequently Asked Questions

Choosing a Dehumidifier
Placing Your Dehumidifier
What is the "Right" Moisture Level?
Where Does Moisture In Air Come From?
Checking the Moisture Level In Your House
Stopping Moisture
The Efficiency Factor
Maintenance and Operating Tips

Choosing a Dehumidifier

Moisture in house air can be a problem when there is either too little or too much. Air that is - too dry - can cause discomfort, dried and itchy skin and nasal passages, cracked or rickety furniture, and sparks when you reach for a doorknob or another person.

Air that is - too damp - can cause itchy skin and nasal passages, ongoing condensation on windows, water damage to materials, mold growth and even rot of wood materials in your house.

Note that both excessively dry and overly damp conditions can both lead to the same problem of dry and itchy skin and nasal passages. In the first case this is because the air is dry and in the second case because it contains mold debris and spores that are toxic.

When you choose a dehumidifier, make sure you know:

The size you need for your house - most manufacturers have sizing charts.
Purchase cost
The efficiency factor
Whether you have to empty the condensate tub or the unit is self-draining.
A self-draining dehumidifier is best, because you don't have to remember to empty the tub every day.

Whether it has an automatic defrost feature - it should have one.
The noise level at low and high speed.
The manufacturer's reputation for quality and guarantees.
The service available from the seller or a local service depot.

Placing Your Dehumidifier

If you have forced-air heating and central cooling and the fan moves the air continuously, it doesn't really matter where you place the dehumidifier. It will remove roughly the same amount of moisture from the house no matter where you place it.

The most convenient spot is usually the laundry room, on a shelf over the laundry sink so condensate drains directly into the sink.There are two reasons for placing your dehumidifier in your laundry room: it can be warm, and dehumidifiers are more efficient in warm air, and there's a convenient drain.

If your basement is cool use a self-draining dehumidifier and put it where it can drain.

If you have hydronic or baseboard heating, place the dehumidifier where you have the worst dampness problem, as long as that location is not cold. If you have automatic defrost, a cool location is okay.

Placing a dehumidifier in a bedroom may not be a good idea. The unit may be too noisy and you have to empty the condensate tub every day.

What Is The "Right" Moisture Level?

Generally, the "right" moisture level - the relative humidity - in your house is less than 50 per cent. At less than 50 per cent relative humidity it is unlikely that mold will grow indoors.

There are cases when 50 per cent relative humidity is too high. For instance, if there is condensation on your windows in cold weather, it's a good idea to lower your relative humidity to as low as 30 per cent.

Another instance: if you, or someone in your family, is asthmatic, you should consider keeping the humidity level in the bedroom at 40 per cent or less.

Dust mites prefer relative humidity of 50 per cent and higher. Dust mites leave debris in bedding, and the debris aggravates asthma. Keeping the relative humidity at 40 per cent or less controls the dust mites and reduces their effect on asthmatics.

Sometimes, reducing relative humidity won't solve moisture problems. Defects in insulation or the air barrier in walls and ceilings can cause cold spots in your house. They show up as areas where there is always condensation, even if relative humidity is 50 per cent or less. A dehumidifier won't solve the problem.You will need help from a qualified builder, renovator or insulation specialist.

Where Does Moisture In Air Come From?

Moisture can come into your home from many places. Outside sources include the soil around your house, surface water drainage and damp outdoor air. Breathing and perspiration by you, your family and your pets is a major source of indoor moisture. So are showering, bathing, drying clothes indoors, venting clothes dryers indoors, washing dishes and floors and humidifiers.

Most houses have more than one source of moisture. Moisture can cause problems once in a while, or all the time. A little prevention can keep excess moisture out of your home's air and prevent both occasional and continual problems.

Checking the Moisture Level In Your House

A "hygrometer" measures relative humidity. A hygrometer is an inexpensive, easy-to-use instrument, sometimes called a humidity sensor or relative humidity indicator. There are mechanical and electronic hygrometers.

Stopping Moisture

Preventing moisture from entering your house is the best way to solve moisture problems.

If you have surface leaks you can fix them by grading the soil around your house. You can fix groundwater leaks by repairing basement or crawl space walls and floors.

Easy preventive measures include shutting down humidifiers, drying clothes outdoors and venting the clothes dryer outside the house. One of the best ways to reduce moisture is to use a good quality, quiet bathroom fan. It vents moisture from showers and baths.

In hot, muggy weather, ventilate your house as little as possible. Air out your house when there's a dry spell and no chance of moisture problems. However, you can reduce relative humidity in dry, cold weather by increasing ventilation. A whole-house ventilation system, such as a heat recovery ventilator (HRV) or an exhaust fan coupled with fresh air intakes, will increase ventilation and dry out house air.

In the summer you can use an air conditioner that removes water from incoming air instead of just cooling it. Look for an air conditioner with a high "latent heat" rating rather than a good "sensible heat" rating.

In regions where there are months of cool, damp weather or hot, muggy weather, ventilation just adds more moisture to indoor air. A dehumidifier is an effective way of preventing moisture problems.

The Efficiency Factor

The Efficiency Factor (EF) is a guide to a dehumidifier's operating cost. The product brochure or operator's manual usually give the EF. If they don't, you'll find the EF on a label behind the water collection bucket.

The EF is the amount of water, in litres, a dehumidifier removes at 27°C (80.6°F) and 60 per cent relative humidity for each kilowatt hour (kWh) of electricity. If electricity costs 8 cents a kilowatt hour, a unit with an EF of 1.2 will remove 15 L (32 U.S. pints or 3.3 imperial gal.) for each dollar in electricity costs. An advanced unit with an EF of 2.4 will remove 30 L (63 U.S. pints, 6 1/2 imperial gal.) of water for each electrical dollar spent.

Because condensation gives off heat a dehumidifier acts as a heat source. This can be useful in spring or fall, when basements tend to be cool. In mid-summer, the heat added by a dehumidifier is counterproductive.

Maintenance and Operating Tips

Clean the internal filters frequently. Start by cleaning them every two weeks. If the filters are not very dirty you can clean them less often. Vacuum the coils every spring and fall if they get dirty. You can't set and forget the controls on a dehumidifier. In the muggy days of summer, set the controls to remove more moisture. Lower the setting to remove less moisture in spring, fall and on clear, dry summer days.

Source: http://www.cmhc-schl.gc.ca/en/index.cfm