O T --Crawlspace Moisture---So Much Conflicting Information!

I live in NW Alabama and, as expected, have a humidity problem. I have a 1/2 Basement under my home and the crawlspace is app. 5' high at the lowest point. There is app. 1300 sq. ft. of crawlspace.
I use the crawlspace for storage because there is a walkin door and plenty of headroom in about 1/3.
Most of the wooden shelving and a lot of rubber and plastic items have a light coating of white to light green mold.
The crawlspace is vented with foundation vents and there is a vapor barrier that is poorly installed. I have thoroughly inspected the dirt, after a heavy rain, and I see no water accumilation or apparent dampness.
Now for the Confliction Information---
I have done extensive reaserch and find that some recommend foundation vents and others back them up by recommending power ventilation.
Of course, these recommendations come from companies with items for sale.
On the other hand, some recommend closing off or covering the vents to disallow moisture from entering. And, of course, they sell these covers.
Where can I get an unbiased opinion??

Take it from someone (me) in far south Texas where humidity is the king, don't believe what all the sales folks tell you. Talk to your neighbors, especially the older ones that have lived near you for a long time. Experience speaks volumes of good valid information!

Both ways have advantages and disadvantages. Let's first consider why/how moisture gets into the space. You have ruled out rain leakage so that leaves condensation and moisture migrating from soil through walls. Anytime moisture laden air comes in contact with a surface cooler than the air,it will condense moisture onto the surface. Enough air flowing through a room will keep room surfaces near air tempature and miniumize condensation. That suggests lots of vents. Problem is that room contents will freeze or rise to tempatures that make it worthless for food storage ect. If the moisture barrier doesn't block moisture migration and you want to maintaine 50*to80*temps year round,I would think blocking air vents and useing a dehumidifyer is about the only option. I would think expense of dehumidifyer might be offset by savings in home cooling and heating since floor tempature will be moderate year round.

I also have a crawl space. I get water down there after a heavy rain and I have a sump pump to handle it. But for the most part it is 65f all year round in my crawl. I have thought of putting a power vent in. But.....I have no mold problems. Warm and dry in the winter. Code requires that you have 1 vent for every 150sqft of floor space. I have 15 or so vents, more then enough. I have heard of people running a de-humidifier in their crawl spaces, Might work for you.

I'm a retired building inspector. The ground must slope away from your house, all the way around. Make sure you have 6" or 8" or more of fall in the first 8' to 10' away from the entire house. You must get all water away from the foundation. Get downspouts to drain completely away from the house. If some adjacent grade slopes down towards the house, get that fixed; no water should be allowed to drain TOWARDS the house. If you don't do all that, all the rest of your efforts may not work. And measure it, don't just walk around and eye-ball it; ground will settle over the years, and what was OK a few years ago not may drain properly now.
Vents need to be at EVERY corner of the crawl space, to get the corners vented; that way the rest of the crawl space gets vented. Put 4 mil or 6 mil plastic vapor barrier down, securely, overlap all joints by a foot or more,a nd secure it down tight. You might put gravel on it to hold it down. If you have plastic down, you need 1 square foot of vent space or more, for about every 1000 sq. ft. of space. might need more. (And measure the actual vent space open area; don't just guess at it. )(They're not as big as you think.)
Without proper plastic vapor barrier, you need 10X the amount of vent area. Yep, ten times.
Keep the vents open all year long, unless in winter you want to close them off.
And yep, you'll still get moisture inside, but it should be alot less.

There is simply no way to completely eliminate moisture from your crawl space. The most important thing is to do everything possible to direct rainwater away from the house. But once that's done, it's still going to be damp. If you seal it off, moisture will still come up from the ground. although a vapor barrier will help. Ventilating it will keep the humidity down a bit, but because of the cooler temperature in the crawlspace condensation is inevitable. Particularly in humid regions like Alabama.

I'd say do what you can to improve your vapor barrier, make sure you've got reasonably good ventilation and accept the fact that you can't store anything in your crawlspace that can't tolerate a little mold and mildew.

You might consider getting a termite company to spray and kill the mold

put plastic on the earth and install a dehumidifier
underneath the house , close of all ventilation.

A lot of high end homes putting hardwood floors in now require dehumidifying crawl space in most areas of country before they will honor warranty on cupping of boards. Been in a few that were dehumified, big difference on odor and moisture, may put one in my house crawlspace in future just to reduce moisture cause for sure mine is no where near high end housing. contractor said for complete install with ducts, yea, pulls from various areas, about $3k

This is another doubled edged sword. It is a real situation in some homes that actually have a moisture problem. The fix can be as simple as plastic and open vents, to French Drains, plastic, bildge pumps, fans, dehumidifiers, etc.

Here is the problem. Greed ruins everything, and the companies selling this have figured out that there can be a hugh profit in it. They are ALL claiming to be "experts" at moisture control. They show up in decaled vehicles that say they are "experts". They take a mositure meter and turn it in to a robbing device.
They use scare tactics and then inflate prices way above a reasonble profit, etc.
They know that a certain homeowner profile, such as an older female living alone being told that her lungs will fill up with mold if she does not have this done, is not going to question the price. They scare the bejeebers out of her.
Too many companies out there doing the scare tactic on a very regular basis.
I have seen quotes of $1,100 to open the vents and unroll plastic under a home that is about 1,600 Sq Ft heated. Ridiculous!!!!!!!
This is for a home that has a very easy access crawl space, and never had any indications of moisture problems but "suddenly" does now.

Crawl spaces are nicer as heat/cool barriers during the summer and winter than having a slab foundation, but the moisture can be a problem and cause problems. I had a home that had a crawl space, and even with vents at all four corners of the foundation just below the actual home, I still had moisture down there because at 4' or 5' down, dirt is natually moist to begin with, and then when you couple that with rain or melting snow being absorbed by dirt, then dissapating or being spread out as its absorbed, hey, moisture is not uncommon into crawl spaces. What I did was bought rolls of plastic that were as I recall, like 20' x 50' x 6 mils and laid them down covering the dirt bottom. I covered it entirely overlapping one direction, and then laid down a another overlpping layer going the opposite direction. Dried it up pretty good, and made a huge difference.

I had two neighbors that did it even better than me. Both pumped soupy concrete into their crawl spaces, paid one of their sons $$$ to be down there to help spread it out as it settled. If I were planning to keep that house, I would have done the same, but the plans were to sell, and I sold it.

I would at least line it with plastic like I did, and if you plan on keeping the house, maybe even put a couple inches of pea gravel down to create a moisture draining barrier first, which is common in the midwest for crawl spaces.

Good luck

Mark

By the way, do not close those vents off. They don't allow moisture in so much as they do air to help dry moisture out, no different than roof vents. Block them off and you guarantee yourself of moisture and mold and then rotted wood.

Mark