DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Insulation and Radiant Barriers > Crawl Space Dehumidifier




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Old 09-04-2013, 12:27 PM  
jhk49
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Default Crawl Space Dehumidifier

I hope someone can help me with a problem that I am having.

I live in southwest Georgia. It is often humid in this area. My house is about 2000 sq.ft. and there is a crawl space under the house. The house was built during the late 70's. We have open vents around the perimeter of the crawl space and we also have a rather old plastic vapor barrier. I do not have a problem with water seeping into the crawl space as a result of flood or rain. I have a moisture problem presently under the house which appears to be due to a slow dripping water pipe. I will have this resolved next week. However, my HVAC repair person did tell me that he thought the insulation on the HVAC ductwork may need to be replaced because he had seen condensation on the outside of the ducts during this hot/wet summer we have been having.

My pest control company recommends that I install a new vapor barrier, encapsulate the crawl space, install a wireless humidity sensor and install a dehumidifier. The cost is about $2200, plus an annual $100 fee for maintenance of same.

I really have three (3) questions:

1. Since I believe that the main cause for the increased humidity in the crawl space to be the leaking water pipe, would it be just about as effective if I did everything BUT purchase/install the dehumidifier? I could use the wireless sensor to indicate if another leak problem occurs under the house.

2. I have read that encapsulating/dehumidifying the crawl space can save as much as 20% in your HVAC bill annually. That sounds very high to me ....... do you know or know of what others have experienced in savings after they have installed a dehumidification system under their house?

3. The pest control company indicated that I have some puddling of water under the house as a result of the water leak drip, outside of a bucket and a sponge ….. is there an easy way to get rid of this puddling after I have the pipe repaired?

Thanks ever so much to anyone who can give me some good advice on this issue.

Jim Kempf
Leesburg, GA



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Old 09-04-2013, 08:14 PM  
nealtw
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Welcome to the site, so the system you have worked fine for 30 or 40 years and because you had a water leak you should spend how much.
If you seal the crawl space you would have to condition it to. So anything that could be airborn there can now get into the home.
If you go looking on this site you can find argurments for it, I am still a non believer.



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Old 10-30-2014, 01:10 PM  
nunyabiz1
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If you live in Georgia and have open vents then its basically the same as having a water leak anyway.
Hot humid air is drawn in by the cooler crawlspace environment and it condenses on every surface.
Open vents are BAD in humid areas.

You need to close the vents, pull down insulation from the floor joist, put down at the very least 6mil poly on the ground, although if you want to do it right so you can forget about it for about 50 years then you need to put down 12 mil multiple layer Poly like a Dura Scrim made of virgin material.
The poly you buy at the local hardware store is good for maybe 6-10 years if your lucky.
Then insulate the WALLS of the crawlspace with a minimum of R10 Polyiso foam board.
If your HVAC is under the house then cut a hole in the plenum and install a vent NO RETURN just a vent to condition the space and it stays bone dry.

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Old 10-30-2014, 04:33 PM  
nealtw
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Quote:
Originally Posted by nunyabiz1 View Post
If you live in Georgia and have open vents then its basically the same as having a water leak anyway.
Hot humid air is drawn in by the cooler crawlspace environment and it condenses on every surface.
Open vents are BAD in humid areas.

You need to close the vents, pull down insulation from the floor joist, put down at the very least 6mil poly on the ground, although if you want to do it right so you can forget about it for about 50 years then you need to put down 12 mil multiple layer Poly like a Dura Scrim made of virgin material.
The poly you buy at the local hardware store is good for maybe 6-10 years if your lucky.
Then insulate the WALLS of the crawlspace with a minimum of R10 Polyiso foam board.
If your HVAC is under the house then cut a hole in the plenum and install a vent NO RETURN just a vent to condition the space and it stays bone dry.
Let's just say we buy your arguement about the humidity. Let's just talk about the no return air in the crawlspace. I'm guessing that is so bad air dosn't come back into the system. How much air do you think you can pump in to a closed room. Maybe you could argue the there is pessure in the ducks that would spead to that closed room. First it would not circulate and what happens to the pressure when the system shuts down.
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Old 10-31-2014, 02:02 PM  
nunyabiz1
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Ours is this way, of course our crawl space has 9' ceiling on one side and 4' on the other so LOTS of air space, but in general I don't think I have ever seen a 100% absolutely airtight crawl space.
The air that is blown in by the HVAC simply leaks out under the door, we also have a vent hole up high where the clothes dryer vent is, I purposely did not seal around this so that air can escape that needs to.

also a flapper valve can be installed up high on the wall that lets air OUT but not IN if need be.

The air under our house right now smells 100X better than it used to when we had vents.
Still doesn't smell like a fresh meadow but WAY better than the moldy mildewy manure it used to be.

And there is no reason to "buy my argument" about the humidity as there have been several scientific studies that pretty much prove that without any doubt.



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