Do I need a de-humidifier?

All,
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.
Thanks, Dan
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I should also mention the basement area is about 700SF.
Thanks, Dan
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i don't think a 25 pint model will cut it. Also check to see how mus square footage the unit is rated for.
wrote:

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on 8/6/2007 9:39 AM lagman said the following:

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.
--

Bill
In Hamptonburgh, NY
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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 relative humidity.
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 components.
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 levels.
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!
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On Mon, 06 Aug 2007 06:23:39 -0700, lagman wrote:

If the humidity is more than 70% in your basement you probably need one.
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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.
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We just had a rainstorm and my digital hygrometer says 56%.. Is this humid enough to justify a dehumidifier?
Thanks, Dan
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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 empty it.

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says...

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 ;-)
Cheers, Banty
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Re Re: Do I need a de-humidifier?:

Good advice.
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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.
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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.
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Paraphrasing. "If Mama thinks the cellar's too humid, everybody think the cellar too humid". Buy the denum and get it over with.
--

Christopher A. Young
You can\'t shout down a troll.
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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.
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lagman wrote:

but my wife thinks it feels too humid
Dan, that is the answer even if she were wrong, which she is not.
--
Joseph Meehan

Dia \'s Muire duit
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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 smell musty.
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.
aem
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