Dehumidifier or exhaust fan in crawl space ?

I have a situation with an under vented crawlpspace . Due to landscaping and architectual considerations, it will be almost impossible to add more vents . I am interested in comments / discussion on installing a basement dehumidifier or or exhaust fan for supplement crawl space dehumidifcation .
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I would seal the thing up unless you have water under there which should be taken care of with perimeter drainage. This whole theory of having moist summer air ventilate your crawlspace is slowly being dumped. All the warm moist air does is condense in the crawlspace and make things worse. Like I said, a wet crawlspace needs a perimeter french drain. But if it is otherwise dry consider sealing it with foam walls and foam boards under the floor joists.

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snipped-for-privacy@nospam.com wrote in

If the crawl space isn't well-contained (like a basement), a dehumidifier will never really conquer the moisture and it will run 24/7. You best bet is good ventilation and a fan strong enough to move all the air through.
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Wayne in Phoenix

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Is the moisture coming from the air or from the ground? In basements, it is usually from the air---it hits the cold basement floor and deposits its moisture. So if you ventilate and allow in more moist air, you get more condensation.
You have a crawlspace and I don't know what's happening there. If there is water seeping into it from the ground, that's a different matter. But I doubt it.
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RPG wrote:

Not really. I have heard this argument many times, but it just does not hold water. Well in some parts of the country that may be true, but in most of the world it is not true. First, it is not moisture on the floor of the craw space that is the problem, and that is the only part that may be cool. The exposed structural members above the craw space are not likely to be cool and yet it is they that get damaged if there is insufficient ventilation to reduce the moisture level to that of the outside air. Generally the ground is more moist than the air.
Many things are tried, but the only one that seems to work well is good ventilation. Power vents may reduce the area requirements, but only if the owner keeps the system going and they tend to not bother fixing things when they go bad and then damage occurs.

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Joseph E. Meehan

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If the floor is cool, that cools the whole room. More importantly, if there is condensation on the floor, the air is in contact with water, and this makes all the basement air very humid. The reason certain elements suffer more damage is that they are more susceptible to damage.
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Do you have plastic on the ground and good drainage around the basement. Is humidity a problem, I mean you have measured it accurately. Every house and area can be different in venting. A dehumidifier sounds like overkill
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Dehumidifiers coils freeze under apx 67f. Sears has one that wont supposidly but it is a risk
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