Crawl space dehumidifier without encapsulation?

[kstu]

Hello fine folks. I am dealing with moisture in the crawl space from the usual suspects: condensation, seeping through the foundation walls, and coming up from the ground. Mold is very minor and the wood is not rotting or anything, so trying to nip this in the bud before bigger problems down the road.

We currently have some crappy 6mil vapor barrier that has a few gaps along with foundation vents (worthless apparently). Had a couple people come out to take a look and provide estimates.

Basically, the first wants to simply seal up the vents and install a dehumidifier and call it a day. The second is suggesting encapsulation along with the dehumidifier as well as a few other things at about 3-4x the cost of the first.

So my question to you is whether or not encapsulation is necessary? Will a dehumidifier alone remediate the problems or will it simply be constantly fighting the moisture and in the process racking up the electric charges and shortening the life of the unit? Bottom line is do I need to encapsulate the crawl space?

Thanks in advance!

 

[bfun_x1]

When I bought my house my crawl space had a dehumidifying setup that looked like a humidistat connected to a fan that exhausted air out of the basement through a tube. It looked pretty simple but I never actually saw it work because we ended up getting the basement treated for radon which involved encapsulation and a different fan that runs 24/7. I was told the radon treatment would now dehumidify the basement. My basement gets water in it a lot and it was designed to be semi moisture proof anyway so I'm not sure if this solution would work well enough for a wood basement.

My last house had vents and my mom's house also has vents. The inspectors said that was enough to keep the moisture away.

 

[Greenman]

It's going to depend on the climate where you live, and how much water leeches into your crawl space. I would guess that without sealing the crawl space, a dehumidifier won't keep up. That's just a guess plucked out of thin air, around here the few houses that have wet crawl spaces are solved from the exterior. We stop the water before it gets under the house.

 

[kstu]

It's going to depend on the climate where you live, and how much water leeches into your crawl space. I would guess that without sealing the crawl space, a dehumidifier won't keep up. That's just a guess plucked out of thin air, around here the few houses that have wet crawl spaces are solved from the exterior. We stop the water before it gets under the house.

Thanks for the reply Greenman. I am in central Virginia. We are absolutely taking other steps to hopefully prevent water from getting in: we will be replacing the gutters, using downspout extensions, and most likely doing some regrading as well. My hope is that this will go a long way in improving the leeching water situation.

I actually think the biggest problem is the condensation from the hvac runs which will hopefully be reduced greatly assuming we can bring the relative humidity down by sealing the vents and getting the dehumidifier going.

This leaves us with the moisture from the ground. I would say the existing vapor barrier gives us about 95% coverage but certainly not sealed entirely. The other thing I'm hoping might work in our favor is that it's not a terribly large crawl space, I think somewhere between 800-900 sq ft. I believe the dehumidifier is designed to handle a much larger area so hoping it should be able to keep up.

Basically, all I'm wondering is whether or not it's completely stupid to just do the dehumidifier without going for the encapsulation, is there any chance of this working? If it was another thousand bucks or something, I think we would go for it, but at 4x the cost it's a lot to consider. I'm also assuming we could do just the dehumidifier now and if we find that it is not keeping up we could always go for the encapsulation later, is that correct?

Thanks again, really appreciate your unbiased input (knowing full well you can't say much with any certainty without actually taking a look yourself).

 

[Greenman]

You can always do it in stages. Start by mitigating water intrusion from the exterior. Once you have that more or less controlled then evaluate the crawl space again. Perhaps at that point increased ventilation will solve the problem.

 

[Red Squirrel]

I would look at conditioning the crawlspace and making it part of the house. Treat it like a basement. The US seems to treat crawlspaces almost like attics, where they don't consider it as part of the house envelope and that causes lot of moisture issues and other issues because unlike an attic, it's in the ground and more prone to moisture. Consider it as part of the overall thermal envelope of the house and have HVAC like the rest of the house. This will encourage proper air movement, and also make the crawlspace climate viable for storage etc. There will always be humidity but by finishing the crawlspace like a basement and conditioning the air it will lower it.

Here's mine for example:



The drycore is a bit overkill, but I just wanted a nice clean floor to walk on as concrete was rough and dirty. I added spray foam in the rim joists, then I plan to put roxul and vapour barrier for the rest. I have a couple hvac vents down there too just to add a basic level of air circulation.

I need to build some decent shelving units or something some day just to organize my stuff better. It pretty much acts as general storage. Since I have so much room it does encourage me to be a hoarder though. Nothing wrong with that if it's organized, but right now it's not.

That hole at the end goes to another crawlspace which is under my garage. That one is a bit more dingy, but I got it fully spray foamed years back so it's actually not too bad. Would be a decent spot to put my batteries if I go solar and would also double as a nuclear fallout shelter if Kim Jong-un gets his aim wrong.