Google Answers Logo
View Question
Q: Humidity ( Answered 4 out of 5 stars,   0 Comments )
Subject: Humidity
Category: Science > Earth Sciences
Asked by: jpeebs-ga
List Price: $5.00
Posted: 04 Dec 2005 08:30 PST
Expires: 03 Jan 2006 08:30 PST
Question ID: 601251
Does humid air rise or fall? That is to say, if I were to install a
de-humidifier in a very high-ceiling space, should it be located high
or low to be most effective?
Subject: Re: Humidity
Answered By: tlspiegel-ga on 04 Dec 2005 10:29 PST
Rated:4 out of 5 stars
Hi jpeebs,

Thank you for your question.

Weather and the Atmosphere

"In a thunderstorm, hot humid air rises, as in ordinary convection."


About Your House - Placing Your Dehumidfier

"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 selfdraining
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."

[Same article]

========= - Dehumidifying and Drying Air Info

"Place the dehumidifier at least 6 inches from the nearest wall where
air can flow freely to and from all sides. Avoid locating it in a room
corner or near a large piece of furniture. Shut all doors and windows
to the area to be dehumidified.

For the first few days of operation, turn the humidistat, if the model
has one, to drier or "extra dry." This aids moisture removal from
furnishings as well as room air. After the area has dried, adjust the
humidistat to your particular comfort level.

Before you empty the water pan or bucket, turn the machine off and
also disconnect the power cord. This eliminates any possibility of
electric shock if you spill water and there is a fault in the
system of the unit or your home wiring. Be sure the area, the unit,
and you are dry before you reconnect the cord.

Dehumidifiers operate most effectively at air temperatures about 70 F.
At temperatures below 65 F frost may form on the coils (which are kept
cold to condense as much moisture as possible). If this happens, shut
it off, and wait for it to defrost before running again. Frost cuts
down air circulation so the dehumidifying process does not work, and
may damage the coils. This problem usually occurs in cool basements in
spring or fall; check the appliance if temperature hovers near that

As water condenses out of the air, heat is given off, raising the
temperature slightly in the area around the appliance. This warmer air
results in a lower relative humidity.


Dehumidifiers need little upkeep or care. The following simple
procedures are sufficient:

Always unplug the power cord before cleaning the unit. For regular
cleaning, dust the grilles or louvers with a soft brush or the dusting
attachment of a vacuum cleaner. Either dust the cabinet or wipe it
with a damp cloth. Every few weeks, scrub the inside of the water
container with a sponge or soft cloth and a mild detergent to
discourage the growth of mold, mildew, or bacteria. At least once each
season, remove all dust and lint from the cold coils with a soft

Always plug a dehumidifier into a three hole grounded outlet. If there
is none where you want to put the unit, make sure you install one
properly. Using extension cords is not advised because if an extension
rests on a damp floor or if water spills on it, is a shock hazard. If
you must use an extension cord, be sure it has a three-hole receptacle
and three-prong plug for grounding. If a three-hole, grounded outlet
is not available, convert it following our instructions and grounding
properly. This is particularly important for a dehumidifier because it
may be operated on a damp floor that could conduct electricity and
because it collects water, which could spill and cause an electrical
accident. Never remove the third prong from a dehumidifier plug ; to
do so invites an electrical accident.

A dehumidifier's fan motor should either be permanently oiled or easy
to reach for oiling; the refrigeration system motor is sealed and
never needs oiling."

========= - 101 Money-saving tips

44. Dehumidifiers remove moisture. Use a dehumidifier in the warm,
humid months to remove moisture from the air. A dehumidifier works
best when air can circulate freely through it. Place it away from
walls and bulky furniture.


Everything You Wanted To Know About Dehumidifiers by Bob Cobe Staff

(see diagram "Drier Home Dehumifier Selection Guide)

Q) What size dehumidifier do I need?

A) Sizing Rule of Thumb for most areas except coastal is: 
Up to 400 square feet: 25 or 30 pint
Up to 800 square feet: 40 pint
Up to 1000 square feet: 50 pint
Up to 1300 square feet: 65 pint

For coastal areas the square foot coverage will be reduced as much as 50%. 
All of these figures are based on an 8? high ceiling. So if the height
is 10?, then add 25% more to the square footage and if 12? high, then
add 50%, etc.


Q) Do I need to place the dehumidifier in the center of the room?

A) Placement does not have to be in the center of a room, but placing
it near the middle would be helpful. Since humidity will equalize
itself in an air space it is not absolutely necessary for it to be
located in the middle of the room.


keyword search:

indoor humid air rise or fall
dehumidifier placement
where to place dehumidifier
dehumidifier room placement


Best regards,
jpeebs-ga rated this answer:4 out of 5 stars
Very thorough response given the terms of the question.

There are no comments at this time.

Important Disclaimer: Answers and comments provided on Google Answers are general information, and are not intended to substitute for informed professional medical, psychiatric, psychological, tax, legal, investment, accounting, or other professional advice. Google does not endorse, and expressly disclaims liability for any product, manufacturer, distributor, service or service provider mentioned or any opinion expressed in answers or comments. Please read carefully the Google Answers Terms of Service.

If you feel that you have found inappropriate content, please let us know by emailing us at with the question ID listed above. Thank you.
Search Google Answers for
Google Answers  

Google Home - Answers FAQ - Terms of Service - Privacy Policy