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Old 12-11-2008, 11:27 AM   #1
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Drying out a crawlspace

Hello all. I'm at my wit's end, but I'm confident someone here can help. Forgive me if I've posted this in the wrong place--it's really a moisture/air quality/ventilation issue, so I thought the HVAC forum was the best place.

I've done a massive renovation to a SFH here in SC, including extensive excavation of the backyard to re-grade the yard so water flows away from the house. Previously, there was a large patio across the back of the house (on the up-hill side) which had been poured above grade. Whenever it rained, water ran right into the crawlspace vents and allowed about 3" of water to settle up under the kitchen. We removed all of that, installed a 55' Keystone block retaining wall with drains in addition to a new patio which was properly leveled to allow for run-off. Also, we installed 2 box drains in the patio as well as extra-large gutters.

Well, today I had a termite inspection (to get ready to get my CO along with the final inspection from the town), and the termite inspector said there's a good bit of water sitting on top of the new moisture barrier (but not under it). There's also 18-20% moisture readings coming off some of the wood. No active termite damage, but I already knew that.

The termite inspector said he really could not find an obvious source of the moisture--but he did say it could be possible that the moisture on top of the vapor barrier is condensation (it's been humid, plus it's been raining hard for 2 days). He said I have to close up all my crawl vents and maybe that will take care of the problem. I always thought you should keep those open to help ventilate the crawlspace--especially since the subfloor is insulated. I only close them in winter when I don't have an insulated subfloor.

He says what I should have done is not insulate the subfloor, but insulate the crawlspace walls instead and air condition the crawlspace like living space. I know that's the new way of doing things, but here in this town, code requires me to insulate the subfloor and lay down a vapor barrier. Of course, at this point, he said the best thing is to encapsulate the whole area. I am not interested in taking on that expense. I'm ready to be done with this project.

So, what the heck am I supposed to do to dry out (and keep dry) this crawlspace??!?!?!?!?!!??! Please help, someone!!!!!

Thanks everybody. :-)


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Old 12-11-2008, 12:40 PM   #2
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It could be that you need to get the air moving. I would try a heating place and ask for an old belt drive blower, might not find one but you can make a direct and give it some time to dry it up drive work just as well put a cord on it that you can get up and out of the water, open the vents for now close them if it looks like rain..... hope it helps


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Old 12-11-2008, 05:21 PM   #3
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I need some clarification. What's a "SFH"? Was the crawlspace existing or part of the renovation?
Easiest thing to do would be to install a dehumidifier in the space. I would then pay attention to this area during and after storms. Were the walls dark and moist or just the ground and wood? You have crawl space vents, are you sure no water is getting in despite the yard work?
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Old 12-11-2008, 06:03 PM   #4
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Ron - SFH = single family housing.

Depending on how much water is on top of the vapor barrier would help in determining if it is condensation. If you are talking about several inches like before I would be inclined to think it is not. I have rented 'carpet fans' before to dry out a crawspace. They have the power needed to dry it out pretty quick. A typical house fan would take forever. Vents should be open to help with air flow. I close them in winter to conserve heat. You need to find the cause of the water intrusion or else a humidifier or the like may not solve your prob.
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Old 12-12-2008, 01:41 PM   #5
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It is the original crawlspace for this old house--built in the mid 50s. The dirt in the crawlspace areas that had been prone to water infiltration due to the previous poor drainage are dry as a bone now. So that makes me happy because I know our efforts have worked.

I really do think this is condensation because the dirt under the vapor barrier is dry. And the moisture on the vapor barrier is not limited to just an area or two--it's everywhere.

I am going to hook up some sort of fan and run it for a few days with the vents open. I'm sure that'll dry things out. Then I'll close the vents and shut off the fan and see what happens.

I get conflicting opinions about the vents--to close or not to close. We're in the northern part of SC (Fort Mill to be specific--just south of Charlotte NC), so we have relatively mild winters (at least compared to the NY winters I'm used to). However, pipes do freeze when we get a few freezing days. So I'm inclined to close the vents in the winter. I guess I'm just going to have to monitor the situation and see what works best.

Thanks for the all the advice so far--send more if you've got it! :-)
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