Crawl space moisture

[bobco]

I have wet insulation and some water on the floor. It is from condensation on the air conditiong ducts, not leakage. We have hot, moist summers here in NC.

I am an engineer but no expert therefore I have read many forums on this topic to acquaint myself with it.

My question is this. Would I get a drying out of the space if I sealed the vents and used an exhaust fan in one of the vent openings? This would create a small negative pressure in the space, drawing some conditioned air from the house. It would also blow off any radon there might be.

Would this avoid the high cost of putting down a new vapor barrier. My original one is torn and parts are missing.

I would like to hear from you (youse) on the pros and cons of this idea.

[Tim123]

Start by Repairing or replacing the vapor barrier, make sure it goes up the wall at least as high as the grade is outside.

While you are in there, consider installing a passive radon vent, you will not have to worry about power.

Are your ducts insulated? if not consider insulating, if your crawl space

Your insulation should have a vapor barrier which is installed toward the heated floor above, unless your crawl is heated.

Crawl spaces in hot humid ares tend to do better if not vented, if you have vents that can be closed, you can give it a try.

Good Luck

Tim

[hausdok]

Hi,

I'm not sure why you'd consider putting down a new vapor barrier "high cost." The barrier material is cheap. If you can stomach crawling around under a house to drag all the crap, including the old barrier, out from under it, and can then spend a few hours scooting around down there with a tub of mastic, a caulking gun and a putty knife, it's well within the capability of most reasonably handy homeowners.

You're in luck; Advanced Energy Corporation has done extensive research into what works in crawlspaces in North Carolina, and, when one wants to, how to seal them properly.

Go here to find a crawlspace knowledge playground.

ONE TEAM - ONE FIGHT!!!

Mike

[Scottpat]

I agree with Mike. Advanced Energy would be a good resource. Adding a vent fan might cause additional problems. Sub floor insulation in the South can cause more problems than the energy you might think you are saving.

How old is the house?

[bobco]

I think I goofed up on sending this reply. What I meant to do was reply to the three replies I got, as follows:

Thanks Tim, Mike, and Scottpat.

I’ll start by answering your questions. The A/C ducts are insulated but they are cool to the touch, and that is where the warm moist air is condensing. The subfloor is insulated with the barrier side up. The house is twenty years old.

Tim, I will take your suggestion to replace the barrier. And Mike, I’m glad to learn the barrier material is cheap. Could someone suggest the kind of places that would sell it, and tell me what to ask for? Is it just 6mm thick plastic? I saw the online ad by basementsystems.com and theirs looks like a special multi-layer composition. I’ll be 84 in another month but I think I can handle that vapor barrier job you described. I might invest in a pair of kneepads though.

Is the mastic used to stick the plastic barrier to the foundation blocks? The Advanced Energy book that was mentioned says to mechanically fasten it to the walls. What does that entail? Nailing it? They also say to leave a 3â€

[Brandon Whitmore]

I’ll be 84 in another month but I think I can handle that vapor barrier job you described. I might invest in a pair of kneepads though.

Please don't take this post to be disrespectful, as I do not intend for it to be. At 84 years old, I am not sure that crawling around in a tight crawlspace (assuming) is the best of ideas for you (rescuers could have trouble getting you out, etc.) I recommend that you hire a neighborhood kid, train him, and have him do most of the work for you. Of course, if I told my grandpa something like this, he would have just smacked me alongside the head and done it himself..........

[hausdok]

Hi Bob,

Brandon's got a good suggestion there; hire some high school kid (or two) to help you out. I've sent you via e-mail some articles written by Jeff Tooley, a North Carolina contractor who specializes in sealing crawlspaces and installing vapor barriers.

ONE TEAM - ONE FIGHT!!!

Mike

[Erby]

I hope I'm in good enough health when I'm 84 to even consider doing this type of stuff myself.

Get a kid to do the dirty work. You crawl around and supervise to make sure he does it right.

He'll benefit from the learning.