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Old 08-26-2011, 10:15 PM   #1
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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??


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Old 08-27-2011, 12:21 AM   #2
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Notice point 3 here:

Home Energy magazine site used to have some free articles up, but searching for them shows they have pulled them. But they were just better written but same info as above.

But it will require more than just covering the vents up if you go that route. Which does have more benefits from it.

But your humid summer air enters that space, and condenses on cool earth and items, probably at some point during the day. If the floor above isn't insulated well, or ductwork going through the space, another place for condensation.

If the floor is not insulated, the conversion would be easy.
Even if it is, you should be able to reuse the insulation on the foundation walls to increase the R-value.


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Giles (08-27-2011)
Old 08-27-2011, 10:35 AM   #3
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"Where can I get an unbiased opinion??" ----- from your local Building Department. In my area, a vented crawl is required. Check to see if you can close off the outside vents or supply conditioned air after insulating the walls and rim joists. Further reading for you:

Closed crawl:

Cover the dirt:

Check local code:

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