Damp under my house need advice??

[2CRUZ]

Hey fellas
My house sits on a slight downward slop and it stays damp under my house all the time. In the summer months I open up al the vents in the foundation and even have a screen frame over the crawl space so air can cerculate under there.Here is the problem the duct work to my central air and furnace runs down the middle with lines to each floor vents. In the summer months the damp smell from under the house comes up through the vents. I've put plastic down all under the house to try to help but the smell still comes up. I'm afraid that it is moldy air and I know that can't be good for you. Has any one else had this probiblem or have some advice as to what I can do? Last summer I left the foundation all seal up and didn't open the vents and it seemed to be a lot better, however I don't think it is good to leve the foundation closed up. Is it?
Thanks guys

 

[djjsr]

Is your ductwork insulated?

 

[SockeyeSummer]

Is the plastic you put down sealed at the edges and seams taped good? If water is running down the slope towards your house could you put in a French drain to divert it? Ductwork should be insulated and tight.

 

[pop pop]

Check the seams in your return air duct first. Then check to see that the vents are sealed to the subflooring. If that doesn't fix it, make sure the plastic is down and tight. After that you may have to ventilate (negative pressure).

 

[kj_mustang]

Power vents
http://www.homedepot.com/p/Master-Flow-16-in-x-8-in-Resin-Power-Foundation-Vent-in-Black-PFV1/202519390?N=5yc1vZc666

 

[2CRUZ]

I don't know if the duct work is insulated or not. I doubt it. I was wondering do those power vents run 24/7? I might look into them.

 

[2CRUZ]

I thought about getting an old blower fan from an old furnace and putting it under the house to get the air moving. What do you think?

 

[scab]

If you have an outlet underneath the house, buy a dehumidifier and empty the tank frequently. I have one in a rent house and it stays dry as a bone.

 

[scab]

Power vents
http://www.homedepot.com/p/Master-Flow-16-in-x-8-in-Resin-Power-Foundation-Vent-in-Black-PFV1/202519390?N=5yc1vZc666

I've always heard that those things aren't worth the money at all. And do you only need one? If you had to replace every vent at $86/ea that would get expensive very quickly.

 

[djjsr]

I've always heard that those things aren't worth the money at all. And do you only need one? If you had to replace every vent at $86/ea that would get expensive very quickly.

You don't install them in every vent. I had a house with 3 vents in a crawlspace and only used 1 fan for ventilating. It exhausted air out of 1 vent and pulled air in the other two. It worked very well for me but my crawlspace was probably moderate to light humidity.

 

[brassmoney]

Those vents need to be open all the time not just in the summer. The downfall is cold floors if they are not insulated. My suggestion is to just simply keep those vents opened at all times and make sure the under side of all the floors are insulated aswell as all ducts and plumbing. Plane and simple..and it will work..those vents are there for a reason and need to stay open!

 

[bczygan]

Good advice above.

Vents always open.

Insulate ductwork and floor system.

Prevent water from up-slope areas from entering.

Clean ductwork.

Check for mold.

Add Electronic filter on furnace.

Better quality filter on furnace and change often.

 

[jdmae86]

I have the same problem in one section of my house (just bought the house in Oct). My problem is that the foundation is concrete block with brick on the exterior. I want to add two vents to that section but how do I go about cutting the block & brick without messing up the structural integrity. The section is my front porch which continues down into the basement of my house. It is really just a small room attached to the basement with no ventilation at all under my front porch.

 

[brassmoney]

The downward slope of your yard is a seperate issue you may need to add a drain in your yard. A french drain will most likely work for that issue and would be the cheapest and you could probably do all the work for both issues yourself.

Shouldnt cost to much if you do all the work for both issues. And its all easy DIY stuff! Fix both issues and you will be all set!

 

[pcmeiners]

"Is your duct work insulated? "
In a past life I ran a large school building. There were numerous large ducts which were inside but uninsulated within the walls, fans run per the original design 24/7 bringing air from the roof area. School finished/opened in the late Spring, no issues, but Fall rolled around and the ducts had major moisture issues, like 5-10 gallons of water pouring out each main roof intake duct every morning on the first floor. Basically, once the moist Fall air's temperature lowered to the dew point, the water condensed within the ducts. Had to add the fan contactors to the building computerized building management system to turn off the fans during the early morning hours (12pm-8am), no issue once that was done.
Anyway, you may have the same action in the crawl space. The ground, wood, ducts are slightly cooler then moisture laden air entering during the early morning hours, dew point hits, moisture builds up. Aside from good insulation on the ducts and ventilation, you might want to consider a timer to kill the ventilation during the early morning hours . Moisture in the ducts in the Fall, Spring and Summer were bad in the building, early Fall, Spring was the worst, Winter was no issue.

 

[brassmoney]

And On a side note...dont be surprised if your water lines freeze in the winter may need to add some type low voltage heater like heat line freeze protection to the pipes to keep them from freezing it happens with that type of set up you have. I remember when I was younger my mothers house had a crawl space like you decribe and every so often the pipes would freeze.

All Said its easy to remedy this stuff!

 

[pattenp]

I have/had the same problem in my crawl space. I put in dehumidifier and a 20" box fan that runs 24/7 on low speed. I keep the vents closed and the crawl space stays nice and dry now. I piped the dehumidifier to the condensation line of my heat pump so I don't need to empty a tank. The power consumption is small and well worth it. One side benefit of the fan keeping the air moving is there are no spider webs. Spiders don't seen to like moving air. I have drain pipe, gravel and plastic under the house, but still had problems with high humidity. When the vents were open in the summer months it got really funky under the house. The other issue I have is a high water table during the rainy season. You can see the moisture condensation on the bottom of the plastic.

 

[Fishplate]

I put in dehumidifier and a 20" box fan that runs 24/7 on low speed.

I've responded to more than one structure fire caused by a box fan running 24/7. YMMV.

 

[HoosierMark]

I appraised an older house where the man was dealing with a rock foundation in a cellar. He installed a bathroom vent fan down by the floor with a pipe to the outside. He then added a vacation timer to turn it on and off. He said he adusted the run times by the humidity factor and had no further problems with dampness. A simple effective solution to exchange the air in the area.

 

[Nowater]

I may add that if household air is hitting the colder ground, household moisture may be condensing on the plastic you installed. Do you have a moisture barrier on your floors similar to the one used on insulated walls?

Can't say for sure without seeing it!

 

[brassmoney]

I know someone who had the power vents for the attic, along the same idea as the fans mentioned for under the house. Bad idea... for him it burned his house down. I would just leave the vents open and see what happens. After all thats why the builder put the vents there in the first place!

 

[pattenp]

I said box fan for a lack of a better description. The fan I have is not one of the cheap $14.99 Walmart box fans. It's a quality fan and has a ball bearing motor. I thought about the fire issue with this extra stuff running under the house so I extended the smoke alarm circuit to under the house and added a smoke detector for added safety.

I've responded to more than one structure fire caused by a box fan running 24/7. YMMV.

 

[b974k]

My house is also on a slope. My crawl space has a concrete floor but the water table around the foundation was too high and the water would seep right through the concrete floor. I dug a 36" deep hole and installed a sump pump hoping the ground water would find a way to it. It did and for 25 years it has been dry as a bone. It used to cycle quite often getting it dried out but now it only cycles frequently when it rains a lot. One thing also I did was create swells around the house to divert the water away from the foundation. If the water is constantly running toward the foundation it will never dry out until summer

 

[benz_dr]

You stated when you shut your vents, it was better. Do research on modern building science and you will find out, treat your crawlspace like a basement, sealed up. Plastic cover the ground good, shut the vents, insulate the crawlspace walls. Install French drains and divert water from the foundation.

 

[2CRUZ]

You stated when you shut your vents, it was better. Do research on modern building science and you will find out, treat your crawlspace like a basement, sealed up. Plastic cover the ground good, shut the vents, insulate the crawlspace walls. Install French drains and divert water from the foundation.

If I keep it closed up it won't do any damage under there? There isn't any standing water under here and there is a drain in the lower end of the foundation. It just seems damp. If it won't hurt any thing I'll just leave it closed up. What do you think?