Page 1 of 2 12 LastLast
Results 1 to 13 of 19
  1. #1
    Join Date
    Dec 2003
    Posts
    287

    What should I do with my crawlspace?



    Here's a pic of my house. That entire 1 story forward portion is sitting on a 3 foot crawlspace that opens to my laundry room (rear lower floor of house on a slab)

    The crawlspace pretty much has a dirt floor. It looks like when it was built they laid down some building paper, but that has all deteriorated.

    My ductwork for the forward portion of the house runs through here as does my kitchen piping but it is all insulated, so it seems there are 2 ways I can go with this.

    Treat it as a mini basement and insulate the walls. Treat it as "outside" space and insulate the ceiling of the crawl (floor of my house).

    In either case I have to lay down 6 mil plastic over the ground, correct?

    Insulating the walls looks like it has more downside with pests and water condensing on the block and stuff. But the crawl I believe is causing a serious humidity issue in my laundry/mechanical room. My trunk line condenses water on top of the furnace, running a little kenmore dehum I had helps, but doesnt completely negate the issue.

    It appears at one time the walls were insulated and it got pulled down for some reason (termites in the furring maybe>??)

    What's the latest and greatest thinking on this? I find conflicting info when I search online.

  2. #2
    Join Date
    Jul 2007
    Location
    Delaware
    Posts
    3,824
    What is the foot print of the crawl space. 16 x 20?
    Are there vents in the crawl space?

  3. #3
    Join Date
    Dec 2003
    Posts
    287
    It's about 25 x 20. There 2 passive vents on the one side that could be closed off if need be.

  4. #4
    Join Date
    Dec 2003
    Posts
    287
    I'm thinking about just laying down the plastic, closing the vents and putting a dehumidifier down there.

  5. #5
    Join Date
    Nov 2004
    Location
    NJ
    Posts
    1,204

  6. #6
    Join Date
    Jan 2007
    Location
    Minneapolis, MN
    Posts
    415
    This is a very complicated issue so go to http://www.buildingscience.com/directsearch/index_html and do some of reading. Do a search on "crawl space".
    Moisture control and reducing soil gases to the space is very important so a vapor retarder (plastic) on the ground is a must with taped seams and sealed edges. Also gutters and proper grade around the foundation to control rain water. I would seal the ductwork and use drylock on the walls and insulate with polyisocyanurate insulation adhered to the walls and seal the vents.

  7. #7
    Join Date
    Dec 2003
    Posts
    287
    This is a very complicated issue
    I've noticed

    I don't like the bats hanging down from the rim joist onto the floor like I've seen some sited propose. My exterminator doesn't like the rigid foam on the block wall. I however think the rigid foam board is the way to go. The only thing that scares me is it looks like this was done at one time and ripped down for some reason. Perhaps because the vapor barrier was non existant. Must have been a long time ago because the pieces of old rigid board looks like a thin rigid fiberglass material, not like celotex they use now.

  8. #8
    Join Date
    Oct 2001
    Location
    Waterford Michigan
    Posts
    2,668

  9. #9
    Join Date
    Jul 2007
    Location
    Delaware
    Posts
    3,824
    If it's a dry crawl space. I would seal all the vents shut, put poly down (thick stuff) Toss a cheap humidity sensor in there (you can get a wireless one at Radio Shack) This will let see at a glance the humidity level down there. I would insulate the floor when I did insulate. This is what I would do. But you may be considering something else.

  10. #10
    Join Date
    Dec 2003
    Posts
    287
    On one of those government funded studies, they tested

    Vapor barrier on ground R19 in the floor

    vs

    Vapor barrier on ground r13 foamboard up the wall leaving a termite inspection strip at the top.

    As far as heating and cooling energy usage they were within 3% of each other with the insulated walls being slightly more efficient.

    I suspect the floor insulation performed as well as it did because you didn't have the cold floors in the winter like you do over an uninsulated crawl.

    I'm starting to lean in that direction, because I'd rather have the insulation up away from the ground and my exterminator whom I've been with for years, and is one of the rare honest guys you'll find in that trade, is telling me he's seen a lot of problems with the wall insulation in a crawl.

  11. #11
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,470
    Most professionals fixing crawlspaces are installing reinforced plastic on the earth. Insulating the walls with foam board to within 6" of the rim joist for termite inspection. Installing a durable, high efficiency, and low temp heavy duty dehumidifier. Suggest 90 pints per day for upto 3,000 sqft of crawlspace. MOst report 50%-55%RH in the crawlspace, elimination of musty odors/sweaty ducks, and a reduction of relative humidity in the home. National companies like Basement Systems/Terminex/Orkin are doing thousands of basements in the green grass climates. Insulation on the bottom of the subfloor will allow condensation between the insulation and the wood subfloor. Results are rotten wood and mold growth. I am biased toward (employed by) the high eff./light commerical defus like Santa Fe/Ultra Aire and others. Dehu TB

  12. #12
    Join Date
    Dec 2003
    Posts
    287
    With rigid foam board the water condenses to the wall and has a direct path to the soil = termites and carpenter ants. That has been my exterminator's experience around here.

  13. #13
    Join Date
    Jan 2007
    Location
    Minneapolis, MN
    Posts
    415
    TB... I am also in favor of eliminating sweaty ducks!

    Billb7581 you are incorrect on your thoughts on condensation and foam board. Go back to buildingscience.com and do some more reading, it is too lengthly to write about in this small space. Also if EPS or XPS foam board is used it must be covered with Sheetrock for a fire barrier so go with the polyisocyanurate (foil faced).

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event