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  1. #1
    Join Date
    Jun 2008
    Posts
    28

    crawl spaces, revisited

    went over to visit my daughter last night and as soon as i walked in the door at their house the high humidity hit me. their a/c unit is a hp, about 5 years old, right now i don't have any details as far as sizing, etc. because my first concern was the crawl space under their house.

    we live in central oklahoma, crawl spaces are very, very rare here. nearly all houses are on slab. their house is older, probably 40 - 45 years i would guess and small, maybe 1000 -1100 sq ft.

    anyway, back to the crawl space. i told her i'd take a look under there....it is uncovered earth, there are about 6 vents around the perimeter.

    i found first, one of the 5" supply ducts from the hp hanging loose and completely open, cooling the unsealed crawl space quite nicely. it should have been connected to a supply register for their utility room but there was never a transition piece made and the round insulated duct was just left open under the house. wrapped the end and sealed with duct tape for now...

    next stop, the dryer vent. the dryer is venting out into the crawl space. there was a dryer vent cover on the side of their house...about 20 feet away from where the dryer is dumping copious amounts of lint under the house.
    i'm dealing with that tomorrow.

    i'm going to have them call the company that replaced the hp when they bought the house and just do a complete checkup, make sure all pressures, airflow and temps are correct to have that end covered.

    i'll run a 4" round duct for the dryer vent and get it out of the crawl space.

    what i'm not sure of is the crawl space vents. open or closed? the earth inside was damp only at the entrance where the cover was in poor condition and over by the dryer vent. there was no pooling or standing water, just dark and slightly moist feeling. because of the cost of sealing the space, it would not be an option for them. so, as it sets, uncovered earth, the open supply duct sealed for now and to be reconnected later, and the dryer dump resolved, should those vent dampers be open or closed? what determines whether they should be opened or closed? i've never lived in a house with a crawl space so i don't know.

    thanks

  2. #2
    Join Date
    Jun 2008
    Posts
    28
    ...bueller.........bueller.........bueller....

  3. #3
    Join Date
    Aug 2007
    Location
    MN
    Posts
    2,680
    keep the vents open in the summer if it is damp. If the ground was dry I would say leave em shut. once the heat run is repaired and dryer vented outside, check the status of the soil, if it is wet still leave the vents open, if its dry shut em and check back in a few weeks. is the crawl tall enough for a dehumidifier? If so leave it closed up and run one for a while. can always lay down rolls of plastic and glue it to the foundation/tape around pipes. I assume the hvac system is in there too?
    You can't fix stupid

  4. #4
    Join Date
    Jun 2008
    Posts
    28
    the ground was dry over about 95% of the earth. it only showed damp by the entrance and at that point the cover was in really bad shape plus I found out they dumped the dogs water bowl right there under the faucet, against the house. the only other dark dirt down there was around the dryer exhaust.

    so I'll have them leave it open for a couple of weeks while I'm gone and check it when I get back. if its better then we'll close it up.

    no, the furnace and ahu is in a closet in the house, also, just found out their heat pump had some major failure 2 years and they had it replaced with a split.

    thanks for the info on the dampers.

  5. #5
    Join Date
    Jun 2008
    Posts
    28
    ...and I assume either way, the vents are to be closed off during the winter months?? sounds like a dumb question but like I said earlier, nearly all homes here are slab construction so I know nada about crawl space etiquette...

  6. #6
    Join Date
    Jun 2008
    Location
    Morgantown, WV
    Posts
    131
    It would behoove you to install a vapor barrier on the crawl space floor. At the very least a covering of 4 mil plastic. I've worked a lot with manufactured housing since the early seventies and state code requires (and has for quite some time) required a vapor barrier on a crawl space.

    My house was built on a crawl space in 1979. It wasn't covered when I bought the house. I installed a 4 mil plastic vapor barrier and the difference in RH in my house was amazing within a couple of days.

    I'm not touting 4 mil plastic as a means to an end. There are better solutions. The bottom line is that any crawl space should NOT be open to open earth.

    Depending upon where you live a radon test might be prudent as well. Keep that space ventilated and make it dry. Put in a vapor barrier.

  7. #7
    Join Date
    Jul 2008
    Location
    Alabama
    Posts
    658
    Quote Originally Posted by merciles View Post
    I found out they dumped the dogs water bowl . so I'll have them leave it open for a couple of weeks while I'm gone and check it when I get back. if its better then we'll close it up.

    Dude....You might not want to leave the crawl open where the DOG can rip up the ductwork!!!

  8. #8
    Join Date
    Jun 2008
    Posts
    28
    thanks dude...i meant i would leave the vents open, not the cover off..

  9. #9
    Join Date
    Jun 2008
    Posts
    28
    Quote Originally Posted by diverdan View Post
    It would behoove you to install a vapor barrier on the crawl space floor. At the very least a covering of 4 mil plastic. I've worked a lot with manufactured housing since the early seventies and state code requires (and has for quite some time) required a vapor barrier on a crawl space.

    My house was built on a crawl space in 1979. It wasn't covered when I bought the house. I installed a 4 mil plastic vapor barrier and the difference in RH in my house was amazing within a couple of days.

    I'm not touting 4 mil plastic as a means to an end. There are better solutions. The bottom line is that any crawl space should NOT be open to open earth.

    Depending upon where you live a radon test might be prudent as well. Keep that space ventilated and make it dry. Put in a vapor barrier.
    makes my stomach hurt just thinking about it....i'm not a fat guy and still had trouble navigating a course under some of the ductwork and drains. i shudder to think of having to try to move around that whole area. but, from your experience it sounds like it might be worth the trouble.

    a question, if the barriers are correct, why would it not have been installed during construction?

  10. #10
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,642
    Cover the earth with plastic and close the vents to keep out the moisture in the outside air in that order. If home is still wet, get a good dehu. Search web for crawlpaces.org?? and buildingscience.com. Research has proven soil and outdoor moisture do not keep the space dry. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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