Dirt crawlspace - vents or no vents?

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Old 06-30-08, 08:30 AM
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Dirt crawlspace - vents or no vents?

I have a dirt crawlspace in the southeast. The house is 90 years old and used the old vent method in my area of knocking out a few of the bricks for ventilation. I went through and added those "automatic" foundation vents every 4 feet that open in the summer and close in the winter. I also just laid down a 6ml poly on the crawlspace. I have no insulation under my joists.

I have one area where the vent actually extends below ground level, so I was looking online for a metal cover to block the dirt from getting in it, and I saw a lot of web sites that said vents are a bad idea in a dirt crawl space. These sites were all selling something, so I wanted to check and see what you guys thought. Should I have bricked up my crawlspace instead and made it air tight? I do have wood floors that get pretty cold in the winter. I'm not concerned about building codes, but am concerned about moisture and preventing termites. Thanks!
 
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Old 06-30-08, 11:53 AM
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I would say to deffinatly seal it up. get a good material, not the 6 mil stuff they sell at the home improvement places.

I'm in coastal SC, and had sealed my crawlspace up not that long ago, the change is pretty amazing. I got my material from a company called YourCrawlspace

It was pretty cheap, and they answered all my questions. I was really happy with the entire process. the work wasn't to bad either. I would suggest looking at their site, and if you have questions, ask them.
 
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Old 06-30-08, 02:00 PM
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Thanks for the reply. So is should remove the vents I put in and brick up the openings? I don't really have a problem that I know of in my crawlspace, just figured I would lay some plastic down while I was under there.

Not sure though if I want to pay a lot of money for a vapor barrier, and yourcrawlspace.com looks fairly expensive. I don't mind spending $300 or so on my crawlspace but not much more than that.
 
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Old 06-30-08, 02:09 PM
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There are two schools on crawlspaces. Some even want you to air condition the space. I just finished laughing at that one, too. Here in the South, the Southern Building Code requires cross ventilation on all crawl spaces, seemingly as you have already done. I find it a fight in futility to seal up an already moisture laden area hoping a dehumidifier and/or air conditioning will keep the moisture down as well as nature would do with cross ventilation. You will have the moisture come up from the ground. That is a given fact. What you do with it is the important thing. Laying down the 6 mil plastic, even up on the walls to the bottom of the vents will help keep the moisture at bay below it. Now all you need to do it remove residual moisture, and cross ventilation will do it just fine. Whatever they are trying to sell, it is up to you to buy. I would insulate the flooring above, and get a window well for the below grade vent. That will help keep water and dirt from entering it.
Don't worry, we have this banter between theologies on this subject quite often, and it is friendly. We just agree to disagree. Airman, you're up!!!
 
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Old 06-30-08, 06:29 PM
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Well I could not resist for long so here goes. I would close vents and seal, install 6 mil poly on ground and up walls to outside ground level.(6 mil is fine your not trying to make living space out of your crawl) Use spray glue to seal and hold insulation. Insulate floor with insulation with craft paper paper side down. If RH is high you might have to run a dehumidifier to reduce moisture.
 
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Old 07-01-08, 09:22 AM
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"Window Wells!" Thanks! I was trying to figure out what those were called so I could find out where to buy them. I think I'll leave in the vents just because it would be such a pain to reseal them. I appreciate the advice.
 
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Old 07-01-08, 10:30 AM
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After weeks of interviewing the ususal crawlspace companies, pest control companies etc; to improve our crawlspace, we are going to go the sealed vent route. We are going to do the work ourselves (much cheaper) and will do the following.

1. put down a vapor barrier as discussed in this forum
2. install a crawlspace dehumidifier (considering Santa Fe Advance)
3. close and seal the crawl space vents

The reason we're decided to seal the vents is that we are highly suspicious that the great majority of the little rain forest and accompanying high wood moisture situation we have going on down in the crawl space is from the humid NC air coming in through our vents and the resulting condensation etc;. When we began to notice the problem in June (bought the house in Febuary in the cooler months) we pulled back the vapor barrier that was there (not a good one, just about 80% coverage with lots of open space) and did not see any standing water and the ground did not feel damp. However, there are puddles of water on top of the barrier and you can see the condensation on the HVAC lines etc;. I've also gone into the crawlspace after every rain and do not see any water that seems to have leaked in via this route etc;.

This is a hard decision and we hope we are proceeding correctly--- you hear so many different viewpoints and get such a hard sell from some of these crawlspace companies. Thank goodness for forums like this--- I learn so much from you guys!
 
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