Crawl Space Vent Covers Bad Idea?

I was looking on the Internet for some Window Wells to prevent dirt from piling up near my crawl space vents. Then I see something like this on the Internet suggesting that the thinking is now to seal the vents to save on energy and keep out moisture?
http://www.basementsystems.com/crawlspace/crawlspace_products/crawlspace_vent.php
What is recommended, to seal the crawl space vents or leave them open for air flow?
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Ventilation is very important. It is much better to properly insulate the floor joists in the crawl space than to seal off the vents. That is what they are there for.
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Ventilation is very important. It is much better to properly insulate the floor joists in the crawl space than to seal off the vents. That is what they are there for.
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Curious, did you read the web page posted? What are you basing your statements on?
It states: If Crawl Space Ventilation Doesn't Work, What's the Solution? There is an informative article by Advanced Energy, a national resource who focuses on applied building science, on venting crawl spaces entitled, "To Vent or Not to Vent." [Download PDF] Crawl space encapsulation is the solution! Seal the crawl space with a vapor barrier, sealer the crawl space vents with vent covers, seal any gaps or holes to the outside, seal the crawl space door - seal it up as tight as possible.
Do you think it is possible that the thinking has changed and engineering is proving the ventilation method is wrong?
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Edwin Pawlowski wrote:

Most modern houses I've seen with crawls don't even HAVE vents. When did Visqueen and similar become widely available? Late 1950s or so, IIRC? In the old days, there was no practical method to seal the dirt with a vapor barrier, and if you had a lot of ground moisture (due to climate, high water table, bad grading and poor footer drainage, etc), venting was the only way to keep it halfway dried out. A hundred years of tradition takes a few decades to fade away. Remember, in most parts of the country, concrete floors in basements (outside of big cities) didn't get common till the 20s and 30s. Of course back then, the cellar entrance was usually outside-only.
-- aem sends...
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on 6/17/2008 11:05 PM aemeijers said the following:

I agree with you there. If the dirt in the crawl space is covered with a moisture barrier, then the vents can be sealed, but if the dirt constantly gets wet from the conditions you noted, then the water vapor is trapped inside, possibly causing rot of the wood above.
--

Bill
In Hamptonburgh, NY
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This poster Albert was only interested in keeping dirt out of his vent space. I think he was concerned about outside dirt or maybe mulch and such. He expressed no worries about moisture or a need for waterproofing or encapsulation. So I told him what I think about ventilation. To simply seal the vent is probably wrong just because the company says it is only a part of a whole system. If it ain't broke don't fix it.
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Read this from the US Department of Energy
http://www.eere.energy.gov/consumer/your_home/insulation_airsealing/index.cfm/mytopic780
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This poster Albert was only interested in keeping dirt out of his vent space. I think he was concerned about outside dirt or maybe mulch and such. He expressed no worries about moisture or a need for waterproofing or encapsulation. So I told him what I think about ventilation. To simply seal the vent is probably wrong just because the company says it is only a part of a whole system. If it ain't broke don't fix it.
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OK I read that thing from the US dept of energy or whatever but it says nothing about ventilation.
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