Garage dehumidifier or crawlspace issue?

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Old 09-05-15, 01:28 AM
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Garage dehumidifier or crawlspace issue?

My garage definitely has a humidity problem. I've ignored it in the past, but this summer we have had lots of rain, and I have mold growing on things in there like bicycle seats and fold-up chairs, and even on metal items.

I gather that I need a humidifier for the garage. So question #1 is where to drain it? I noticed there seems to be a PVC drain that the water heater relief valve goes down into. How would I tie into that, or is that a bad idea?

Then question #2 is that my termite guys tell me the crawlspace is really moist and that I should think about doing something about that. The garage isn't ventilated, so I see those as separate issues, but are they? What do you do to address moisture in the crawlspace, and is it possible that by itself would resolve the garage issue?
 
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Old 09-05-15, 03:48 AM
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I think I would do the crawl space first with a dehumidifier. You'll get results within a few days. Then if need be do the garage. And yes you can drain the unit into the PVC water drain.
 
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Old 09-05-15, 04:16 AM
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Can you increase the ventilation in the garage and crawlspace? I agree the crawlspace is the #1 priority!
 
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Old 09-05-15, 04:33 AM
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Hi toddler,
IMO you are caught between a rock and a hard place. If your outside moisture level is high, it is difficult to get the inside areas much lower. In the garage I will assume that the only moisture you are adding comes from parking wet cars inside, no cooking or showers. But a garage will leak air faster than a house which experiences all new air every 3 hours or less. Run your dehumidifier until the RH is lower and turn it off and you are back to where you started (almost) in 3 hours. Avoid wet cars or any other source of moisture in there and add ventilation, especially if you get a dry(er) spell.

As for the crawlspace, does it have a dirt floor? If yes, that needs to be covered with a black (opaque) vapor barrier to eliminate moisture from the soil. Then you will at least be dealing with just the moisture in the air.

Two options. One, ventilate the crawl and hope the outside moisture level doesn't cause a problem down there. Or two, insulate to the outside and air seal the crawl space and then share some of your AC to condition that space. Once a VB is sealed over the ground and the perimeter insulated and sealed between house and foundation, that space will no longer be an issue and will be a minimal addition to your ac/heat load.

Bud
 
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Old 09-05-15, 12:03 PM
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I actually don't use the garage other than for storage. I open the door for about 60 seconds twice a week when I wheel my trash can to the curb and back.

Interesting idea about sealing the crawlspace and using the ac/heat down there. I don't know if it's bare earth (I've never even looked in there) but I suspect it is.

I don't know why moisture is such an issue as I have a flat elevated lot, but I have horrible mildew issues on the north side of the house. It gets on the deck and anything I put on it, the kids' playset, and the siding of course. I have moss growing instead of grass in spots up against the foundation on that side.

So who would I call about a vapor barrier? Is that a handyman, HVAC or who specializes in that? If I'm going to do this, I want it done right.
 
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Old 09-05-15, 12:26 PM
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Local lumber yards usually see all of the contractors in a given area and often will have a name or two to suggest.

High humidity and limited sun light will certainly grow mold and moss. A lawn specialists would probably be able to advise on an approach to grow grass in those shaded areas.

As for the play sets and other things outside, even without rain, they will get soaked by condensation. Do you have a lot of trees blocking the wind?

Venture down into that crawlspace and see what is on the floor. Inspect the floor joists for signs of mold. Are there any vents, are they open or closed?

Look at the plumbing and check for leaks. The cold water pipes may be dripping from condensation. Is there a sump pit with pump? Any signs of water issues?

Bud
 
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Old 09-05-15, 02:53 PM
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I'll take a look in the crawlspace. The vents are all open. I have no trees in my yard, not one, and I have absolutely no shade. I live on a hilltop, on a flat lot, slightly graded to drain away from the house, where there is a berm that takes any runoff into a drain that goes to a retention pond. It baffles me how I could have any moisture problem given my location. It seems like my scenario is really the best case scenario and yet I am experiencing a lot of moisture for some reason.
 
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Old 09-05-15, 02:54 PM
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If mildew is going to be an issue on the exterior it will almost always present itself on the north side, lack of wind will make it worse. While extra mildewcide can be added to paint often the best defense is regular cleaning of that side of the house. A bleach/water solution applied with a pump up garden sprayer and then rinsed off can make a big difference.
 
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Old 09-05-15, 04:28 PM
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@Toddler "It seems like my scenario is really the best case scenario"
In a dry climate you would be correct. What you are missing is the moisture in the air. You live in a swimming pool (kind of). but whenever the air reaches the dew point you will have condensation.

How long before a glass of ice tea starts to drip water on mama's coffee table? Metal items cool off at night and form condensation. This morning I went out early to unload my canoe from a fishing trip yesterday. The canoe was dripping everywhere and never a rain cloud all night. I dug out an old saw blade from one of my storage sheds, it will need a wire wheel to bring it back to usable.

Your choices are to enclose desired areas and condition them or ventilate as best you can, especially on dryer days. Remember, monitor the dew point as it is a better indicator the moisture in the air.

And cleaning that North side as Mark suggested is about the only solution. Before the end of summer I will be spraying the north side of my foundation as well.

Bud
 
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Old 09-05-15, 11:14 PM
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I understand the climate. I meant best case scenario for where I live (no trees, no shade, good drainage). Not sure why my crawlspace and garage would be so moist whereas my neighbors aren't dealing with the same thing.
 
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