I'm trying to decide whether or not to invest in a de-humidifier. I
just bought a house with a finished basement (first house I have ever
had with a basement). When we were looking at the house, I noticed
the previous owner didn't have one in the basement. I think it is
comfortable, but my wife thinks it feels too humid (we have had a
couple weeks of very humid weather).
My main concern is mold growth. I am going to put a hygrometer down
there to measure the humidity. At what level should I be concerned?
I should also mention that once our furniture gets here, it will
contain a big screen LCD TV and some stereo equipment (I'm not sure if
a humid basement can damage electronics or not).
If I do need one, is there any advantage to putting a lot of money
into one of these things? I see a 25 pint model at Lowes for $139.
My computer and my workshop is in the basement, and has been for many
years. I must say that my basement is underground except for a couple of
feet where it sticks out of the ground on two sides (it's a half
basement). My basement does not always feel humid here in the NE US, but
I do have a dehumidifier that is rarely used, most times after having
the basement windows open on nice summer days. I have insulated,
studded, and sheetrocked walls covering the poured concrete walls, and a
dropped ceiling, so that somewhat protects against outside humidity
getting in. I also have an exterior door between the basement and the
bilco door. Because it is mostly underground, I do not need additional
heating or AC. The year round temperature down here is between 68 and 76
degrees (F) regardless of the outside temp. I do get some ambient heat
in the winter from the furnace in the utility room, and whatever AC air
slips under the door from upstairs in the summer.
In fairly cool climate with only a couple of months of warmer moister
weather; we have a basically unfinished below ground basement,
concrete walls, mainly used as a workshop. Also the washer and dryer
are down there along with the hot water tank etc. It stays pretty well
at a ground temperature of about 60 deg. Fahrenheit hardly ever
dropping below 55 deg. F. even in mid winter. It is heated only when
we are down there working on something.
During this warmer more humid weather some of the outside air
inevitably gets into the basement and since it is cooler raises the
We a have low cost dehumidifier (IIRC it was about $150) running
continuosly at this time of year. Currently it is removing several
litres of water per day which serves to avoid dampness and/or slight
rusting of our tools.
As the outside gets cooler any air getting into the basement will be
cooler and our dehumidifier will run less often
If you intend to live in and heat the basement you may not need to
dehumidify. Might also depend on your heating system. Hot air oil
(gas?) furnaces used to be common and often incorporated humidifiers.
Raising the temperature even a few degrees, usually by means of an
electric heater, can drop the relative humidity quite dramatically.
Warmer air can 'hold' more , moisture.
That heating technique was quite often used in tropical countries
before the common advent of air conditioning to avoid dampness in
telecommunications equipment. Tube type radio equipment used before
the common availability of transistors usually generated enough heat
to keep itself dry. As computers, radios and and TVs have got more
'efficient and if rarely used, they use less electricity and so,
sometimes, may be more liable to absorb moisture into their
The idea of using a hygrometer is a good one. If you get to the stage
of mould you could get problems, possibly health and structural!
Note; We once had the air conditioning fail in a telephone equipment
building; it was also raining continuously. Borrowing a hygrometer
from the local university we took various measurements. No problem at
all; the heat from the switching equipment was raising the temperature
by more than enough to keep relative humidity e well below unsafe
What would have worried would have been if the power failed completely
and the whole building cooled down so eventually dew could have formed
on the equipment!
Your wife is likely right, if it feels humid it is. Get a digital
humidistat or an analog you calibrate, analog are usualy sold 10-15%
out of calibration. 55-60-% is comfortable. a 25pt may do it, Buy
where you have an exchange policy, you dont want it to cycle every few
minutes, nobody can say what you need, if you are only 70% after rains
a 25 pt may be fine.
Yes, soon or later you will find mold on things. Worse time of year is late
spring when your basement is cool from winter but outside air is becoming
warm and humid. I have been happy with mine from Sears. At least they
still stand behind their products better than Lowes or Home Deport which
don't have their own brands.
Fortunately I have a drain in my basement floor by my dehumidifier so I
could connect a hose from the water tank so I don't have to remember to
That the previous owner didn't have one when you looked at the house for sale,
does *not* mean he didn't use one. He just didn't want it around during the
sale sitting there screaming "humid basement, humid basement" ;-)
Now, at least around here, just about any basement has some humidity. So do
invest in one. Mine is from Sears and has a humidistat. It doesn't go on
unless it's needed, and I can set it.
Mine from Sears was a little more than that.
Truly, don't chinz on this - get one even if you don't need it year round. Its
cost will pale next to everything else you'll need to deal with over the years
as a homeowner ;-)
It will help, but not be enough for any basement. But the best way to
control excessive humidity in a basement is to make sure your basement
has a cold air return back to the forced air HVAC system. This way in
the summer your AC system will be able to suck a good amount of it's
air supply from your basement and pump it up into the rest of the
house. If your AC air handler is already located in your basement, an
easy way to provide this is to simply keep your furnaces filter door
opened during the summer months. The AC will then suck a lot of air
from the basement (this wont bypass the filter BTW). This method
helps my basement more than any little dehumidifier can and keeps the
RH the same as the upstairs.
Of course keeping the filter door off would just be a temporary thing
to prevent mold until you can do it right. Ultimately you would want
to install a couple of cold air returns in the basement properly.
When basement homes are built, the HVAC guys usually dont bother
putting adequate return vents there because it's not considered living
space at that time. But when it is remodeled you need to add more
cold air returns.
I'd stay away from the Chinese made LG brand de-humidifiers though
which are all over the home stores now, lot of returns on those,
mostly freeze ups making them useless. I like Whirlpool or GE which
are harder to find.
Look at it this way- they are fairly cheap, even if you buy it new. (I got
mine in like-new condition for 15 bucks at a Goodwill store). If you have a
sump pump or working floor drain, you can graft an old garden hose section
onto the drain tank by cutting off the end of the molded plug, and
set'n'forget. If, after a year, you realize the thing never runs, you can
sell it in your yard sale. But I would keep it just in case- if you ever get
a flood from a busted pipe or rainy spring weather, you'll want all the
drying power you can get.
If you need it, it really makes a difference. I bought mine due to definite
musty smell in basement. Emptied tank every other day first summer. Having a
drought this summer, so empty once a week or so. And the basement doesn't
Or did you mean one of those fancy ones plumbed into the furnace? I'd try a
cheap stand-alone first, to see if you really need it.
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