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Moisture in crawl space/cold rooms


denutza's Avatar
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CAL

01-11-13, 05:56 PM   #1  
Moisture in crawl space/cold rooms

About 2 years ago I had a plumbing leak in the crawl space that went undetected for quite a while.

The plumber dug a hole on the side of the house to pump at all the water that had accumulated in the ground.

There is still a slight dampness on the top soil in the crawl space where the leak was. And the rooms above it are colder than the rest of the house.

The crawl space is vented...Has about 10 vents around it.

I thought about sealing the vents and laying down some plastic to seal the moisture. However I think this (not sure) is against California code, and there seems to be some really mixed opinions around the internet on whether this is wise to do.

Another idea is to just put some fiberglass insulation on the top of the crawl space. I don't think the wood is wet above the damp soil, so I don't think the insulation would get damp (once again Im not positive).

My last idea would be to run a dehumidifier in the crawl space. Maybe dig another hole on side of house and see if any more water fills the hole. Id probably have to wait for spring to do this.

Help!

 
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denutza's Avatar
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01-11-13, 07:22 PM   #2  
Also wanted to add I have some of the RadiantGuard reflective stuff I could use as well.

 
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01-11-13, 09:08 PM   #3  
Welcome to the forums!

You have a lot going on there! Without being able to see it, it sounds like you need to make sure, first of all, that all stormwater runoff is draining away from the house. That hole the plumber dug just might be acting as a sump now, and bringing water back into the crawl space.

Once you have that fixed, you can consider laying plastic over the dirt in the crawl space. I would not, under any circumstances, close the vents. The dehumidifier sounds like a waste of money if you have ten operating vents.

Fiberglass insulation installed between the floor joists might help. Use the batts that are faced with a vapor barrier if you are in a net heating climate. The vapor barrier should go up If you are in a net cooling environment, unfaced fiberglass would probably be better.

 
resercon's Avatar
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01-12-13, 05:15 AM   #4  
Gas Law

Addressing the source of the moisture problem is by far the best advice and checking with your local building code department as well.

The "Gas Law" states that in order for a liquid to evaporate (liquid to vapor) the liquid must be absorbing heat. For a vapor to condense (vapor to liquid) the vapor must be losing temperature.

If we apply this to your situation, the moisture in the ground evaporates inside the crawl space. The only source of heat inside the crawl space is the room floor above it. It will literally used the heat from that floor to cause the evaporation. Thereby lowering the temperature in that room.

What moisture barriers (plastic sheets) on dirt floor in crawl spaces do is prohibit evaporation. To change states from a liquid to a vapor requires a considerable amount of heat energy. For example, to raise 1 pound of water 1 degree Fahrenheit from 210 degrees to 211 degrees requires 1 British Thermal Unit (BTU). However to go from 211 degrees to 212 degrees (temperature in which water boils and creates steam vapor) requires 970 BTU's. This is because it is changing the state of the moisture. This is also known as the "Latent Energy of Vaporization"

Insulating the floor above the crawl space is also a good idea. Again check with your local building department to confirm which applications are acceptable.

 
denutza's Avatar
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01-13-13, 08:19 AM   #5  
So to be clear, leaving vents open with a plastic vapor barrier on the ground and fiberglass insulation on the joists is just fine? I will also assume with the vents open that getting a "perfect" seal on the plastic isn't necessary as to prevent Radan from entering house.

Also,how do I determine if Fresno is a net-heating or net-cooling climate?
It probably averages around 95 in the summer and 40-45 in the winter.

 
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01-13-13, 04:12 PM   #6  
So to be clear, leaving vents open with a plastic vapor barrier on the ground and fiberglass insulation on the joists is just fine?
No.
Posted By: Nashkat1 you need to make sure, first of all, that all stormwater runoff is draining away from the house. That hole the plumber dug just might be acting as a sump now, and bringing water back into the crawl space.
Once you have done that successfully, the dirt in your crawlspace should be dry.

At that point, you can install unfaced insulation. insulation with a vapor barrier mounted up, or insulation with a vapor barrier mounted down, under your floor. The orientation depends on whether you are in a strong net-heating, or strong net-cooling environment. (See below.)

I will also assume with the vents open that getting a "perfect" seal on the plastic isn't necessary as to prevent Radan from entering house.
You should not need to lay plastic on the dirt for energy efficiency or comfort purposes. You should leave the vents open.

If you suspect you have radon in your house, test for that immediately and take the appropriate remediation steps.

Also,how do I determine if Fresno is a net-heating or net-cooling climate?
By asking. Since you asked, it's a net-heating environment: California Climate Zone 13.

Note that that pdf for California Climate Zone 13, from Pacific Gas and Electric. includes a chart showing "Title 24 Requirements" for insulation values and other improvements, and that that chart doesn't mention insulating the floor.

For the best idea of the optimum insulation values for your house, you can plug the data for the house into a calculator such as the ZIP-Code Insulation Program.

 
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