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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. You can adjust
and control the relative humidity
in your house. This About Your House suggests some ways of avoiding problems
caused by air that is too damp and tells you how to select and use a
dehumidifier. What Is Relative Humidity?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. Catastrophes - such
as plumbing leaks or floods - can cause serious problems very quickly. You
will need emergency repairs to deal with them. Checking the Moisture Level In Your HouseA "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. A mechanical
hygrometer usually costs $10 or less. Electronic hygrometers cost $35 to $60. Stopping MoisturePreventing
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. Dehumidifiers And How They WorkHeat Pump DehumidifiersDehumidifiers
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 DehumidifiersThis type of
dehumidifier is designed for hot, humid climates and is not really suited for
use in 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 hot, damp air outdoors
through special ducting. A chemical
adsorbent dehumidifier uses more energy than 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 DehumidifierSome 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. Because the salt
runs off with the water removed from the air, it must be replaced.The system has
no moving parts. If you try this
homemade dehumidifier, remember that salt is highly corrosive to metals and
quite hard on the skin. Dehumidifying VentilatorsThis type of
dehumidifier has a sensor-controller and exhaust fan.You set the
sensor-controller to run when humidity reaches a set 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 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. Dehumidifier Purchase CostsHeat 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 $50 to $100. The more water a
dehumidifier holds - which is measured in litres or 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 house 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 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. The Efficiency FactorThe 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, which it does in many parts of 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. Total CostTotal cost
includes the purchase price, operating and maintenance costs and repair costs. Assume you pay
$350 for a dehumidifier with an efficiency factor of 1.2.You use it 80 days
a year for five years. It removes an average of 20 L (4.4 gal.) every day, a
total of 1,600 L (617.8 gal.). Your cost is $177 a year. A more efficient unit,
with an efficiency factor of 2.4, costs $500. The yearly cost is $153. $24 less
than the EF 1.2 dehumidifier.
Choosing a DehumidifierWhen you choose
a dehumidifier, make sure you know:
Placing Your DehumidifierIf 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. Maintenance and Operating TipsClean 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. When A Dehumidifier Doesn't Solve The ProblemA dehumidifier
alone may not solve severe moisture problems in your house. Your first course of
action is to find the moisture source. Take steps to reduce the amount coming
into your house - or to stop it completely. Remember: a dehumidifier is
useful - but it isn't magic. | ||||||||||||||||||||||||||
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