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Hmmmm ...

Posted by Jay J on July 9th, 1999 10:30 AM
In reply to condensation in crawl space by Kathy Cabana on July 8th, 1999 04:57 PM [Go to top of thread]


With what you're describing, the fans are your first problem. Get rid of them. Warm/hot air has moisture in it. By using them, you're only adding to the problem. After you toss the fans, perhaps the ouside air is being drawn in when the A/C unit runs because you have 'leaks' into your living space. You see, when your heater and/or central A/C turn on, they normally draw in air through return ducts connected to the system. If the pressure in the house sufficiently drops, outside air is pulled into the home to make up for the difference. Hence, air from your crawlspace is being pulled into the house and its air is being replaced by the warm, outside air coming in through your vents (assuming you got rid of the vents). The cycle is complete in that air-in = air-out. Therefore, you must have air leaks to the OUTSIDE as well in your home to complete the air-in = air-out equation.

Again, assuming the fans are gone, one other cause of the puddling is that you have HUGH vents into your crawlspace. Usually, they're about 9" x 12" (approx) in size. You need one of these for about 200-250 sq. ft. of crawlspace. If you have too many, then I can see how the air essentially blows through your crawlspace. (It's like opening the screened windows to your home on a nice day.) If there are too many vents, it's basically an outdoor crawlspace!!! For what it's worth, I have a 30' x 15' crawlspace. It's properly sized for 2 vents of the aforementioned size. Heck, where I live too, the wind blows even on warm/hot days but my joists above the space are dry. No fan(s)!

Once again, assuming the fans are gone, one other cause of the puddling is that you have a dirt crawlspace. (You didn't mention it.) If you do, you should line it with 6 mil. thick plastic suitable for ground use. Then put some bricks or something on the edges to hold it down. (The Hardware Store or Home Center can help you with choosing the right plastic.) Whatever moisture rises to the surface will condense and be reabsorbed by the ground under the plastic. W/O it, it may be drawn into the house or simply condense on the surface. This can be unhealthy.

My approach: Get rid of the fans. If you have a dirt crawlspace, cover it. Then see if you can tell where you have leaks from your crawlspace into your living space. (Usually, winter is best to determine this because you'll feel for cold air around the walls and such.) Insulate the crawlspace better where there are leaks. (Hopefully, your crawlspace is INSULATED underneath for starters!) Then, take a look at the # of vents per sq. feet and solve that.

My best to ya and hope this helps. If I'm way off, please inform me w/more info. (Crawlspace size, size of vents, number of vents, dirt/concrete, insulated underneath or not, what have you done so far, etc., etc..)

Jay J

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