Will exhaust fans effectively remove moisture from my crawl space?

Question

This is a highly debated / discussed topic, but pretty much all of it based on parts of the country with relatively very high humidity.

I live in San Diego, where humidity is moderate most of the year (60 - 80%). Due to grading issues my crawlspace gets wet during rains. I have decided to do a French drain, sump and vapor barrier.

Question is: will a few ventilation fans in the existing vents (and seal the rest) suffice to control humidity in my area? Or should I seal of all the vents and put in a dehumidifier?

I understand it is actually the dew point differential between the outside and inside that matters, but I am unable to gauge what factors could lead to my crawl space having a lower dew point that the relatively low dew point you find in San Diego most of the time.

FYI I don't have an A/C in my house and the heating ducts run through the attic and not the crawl space.

Thank you!

...Also, fix the "grading issues" - attack the primary problem at it's source. — Ecnerwal, Apr 28 '23 at 11:41
No one can say because it depends almost entirely on the frequency and severity of the rain. — isherwood, Apr 28 '23 at 12:48
@Ecnerwal fixing grading is easier said than done given the different considerations in play especially the cost — SAS2Python, Apr 28 '23 at 20:04

score 3 · Accepted Answer · edited Apr 28 '23 at 12:42

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Fans are usually much cheaper to buy and run.

I would start with one or more fans and try it out for a decent amount of time (more than a month) and see if you are happy.

You might want one of those desk/floor fans that move to mix up the air at the opposite end of the exhaust vent.

edited Apr 28 '23 at 12:42

isherwood

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answered Apr 28 '23 at 09:55

crip659

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Sound advice. guess got to try starting from simpler solutions and take it from there. Thanks – SAS2Python Apr 28 '23 at 20:04

score 0 · Answer 2 · answered Apr 28 '23 at 12:42

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The general recommendation here in Sweden is to use dehumidifiers, the reason is that the outside air will be cooled in the crawl space. When hot moist air is cooled, a sharp increase in humidity or, in the worst case, even condensation occurs.

answered Apr 28 '23 at 12:42

Rsf

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Will exhaust fans effectively remove moisture from my crawl space?

2 Answers2