Latest Discussions : Basement & Foundation


06:44PM | 08/09/03
Member Since: 08/08/03
2 lifetime posts
I paid a visit to the crawl space under my house the other day and found it very wet. It was not wet from the outside water getting in - but from moisture condensing on the cool A/C ducts and pipes (I have had the A/C running non-stop in the house for the last month). The condensate drips down onto the poly sheeting and forms puddles, increasing the moisture in the crawl space. I am beginning to get fungus on the floor trusses.

I live in the hot, wet, and humid coastal area of Virginia. I have previously taken steps to keep the rain out such as poly sheeting over sand (above outside grade) piping all downspouts away from the foundation, and ensuring a good slope away from the house. I have foundation vents (open in the summer - close in the winter), but I'm not sure I have enough.

I am considering adding power vents, but logically, it would seem I would be just pumping more moisture through the crawlspace!

I have rented a carpet fan and set it up to blow into the crawlspace to increase airflow. I was going to try that for a few days and then check on things. If it seemed dryer, I was going to assume more airflow is good and purchase the power vents.

I have also read that completely sealing the crawlspace (block vents, more poly, no air flow) is now accepted as an option as this should keep the humid air from entering the crawl space.

I would appreciate any advice and assistance.
Thanks in advance,

plumber Tom

11:06AM | 08/12/03
Member Since: 05/10/03
801 lifetime posts
Remove the hard rigid ductwork, and install flexible insulated ducts to the register boots in the crawl.


01:46PM | 08/12/03
Member Since: 08/08/03
2 lifetime posts
I have "rigid" trunk lines for the supply air, with flex duct branching off to the individual registers. The return duct is rigid also. What would be the advantage to installing all flex duct?

I have been blowing air into the exterior vent now for 3 days... it's dried out some, but still dripping from the ductwork. It would appear that forcing more humid air into the crawlspace may not be the solution!!

Thanks for any replies...



07:54PM | 08/12/03
Member Since: 01/28/03
693 lifetime posts
You have things 'backasswards'.

In warm humid climates such as Virginia, you need to keep foundation vents CLOSED IN SUMMER and OPEN IN WINTER!

Closed in summer to prevent warmer, moister air from entering a cooler crawlspace and condensing...

Open in winter to allow warmer, moister air to LEAVE a crawlspace and prevent condensing...

No kidding....

Someone gave you VERY BAD advice....

[This message has been edited by homebild (edited August 12, 2003).]

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