Results 1 to 6 of 6

Thread: Crawl space insulation help

  1. #1
    Member
    Join Date
    Apr 2006
    Location
    on the Little Su...
    Posts
    32

    Default Crawl space insulation help

    I am helping a buddy finish his project, and we have a few days before fishing season starts. The cabin in the upper Mat-Valley, and it's a 12X16. The crawl space is about 2 feet off the ground ,with the siding coming to the ground and an access hole to get under. The floor joice's are 2x6 on 16"centers. There's not alot of room to work, but can be done.

    The problem is the past owners put regular insulation in between the joice's then capped it off with a plastic vapor barrier, I think it's 6mm, the thick stuff.The critters have made a Mega Mess of the whole thing, and his floor is really cold. All the material will be new. I was thinking that the vapor barrier should be on the warm side and not on the cold side, meaning that you should start with a vapor barrier first then insulate. We're scratching our heads trying to come up with a bullet proof setup.The crawl space pony walls are not insulated ,and theres no vapor barrier on the ground. Here's what we are thinking ,but sure could use some advice/help

    Start by stapling foil bubble insulation to the underside of the subfloor, or thick plasticbetween the joices,then putting the insulation in and then possible stapling chicken wire to keep critters away, Or to start with the foil bubble wrap or plastic and then put about 6" of blue board, glued and foamed in on the edges. Thanks for the help and advice

  2. #2
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,293

    Default

    I'd use faced R19 batts and staple them through the facing with the facing side up to the subfloor and gently pull the fiberglass back to fill the thickness. It won't take many staples. Then I'd sheet the floor with 1/4" plywood leaving about 3" of gap at the edges. Cover the gap with screen and put some nailers over the screen edges using 1x2 or ripped plywood. That's exactly what I did and it works great.

  3. #3
    Member
    Join Date
    May 2007
    Location
    homer
    Posts
    42

    Default deck insulation

    Its very common to just put fiberglass between joists and wire mesh under it to keep varmints out. Then put your heavy vapor barrier on the ground. This makes it nicer to work on the ground under the cabin. 6" of blue board would serve you better on your pony walls or skirting. That 1/4" plywood would work well too, just a little more money. Your concerns about vapor barrier are valid but there is a difference between walls/roof vs floor. In a crawlspace warmth from the house is rising and trying to bring moisture from the ground with it, so you want to stop it at ground level. Usually the temperature difference is'nt as drastic. In a wall or roof you want your vapor barrier in the inside of your studs or joists. Heres the logic, lets say it was done backwards and the vapor barrier was on the outside of the wall. Warm moist air migrates through the wall and the insulation hitting the cold vapor barrier and condenses. Now you have water trapped inside your wall.

  4. #4
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,293

    Default

    You need the vapor barrier to be where the insulation is. If you insulate your pony walls and use a ground cover don't insulate the floor. This is a common practice where the house is heated all the time. In a cabin that'll see heat only when you're there, insulating the floor itself will be the better option. The cabin will heat faster and the floor will be more comfortable. With an insulated floor I'd suggest some vents in the pony walls, too, unless you're fond of mildew and rot.

    Squirrels, birds, and voles don't even slow down for chicken wire. Light gage screen wire will have holes chewed in it quickly as well. I learned the hard way.

  5. #5
    Member
    Join Date
    Apr 2006
    Location
    on the Little Su...
    Posts
    32

    Default

    Thanks for the ideas. The pony walls are not insulated, and the crawl space is anything from airtight, so hopefully we will not need to insulate the pony walls or put down a ground cloth??. But if it would be the best, it should be done. The plywood is a great idea also, but there are several(11) pier blocks with 4x4 posts scattered, it would be a real pain to plywood it in, but I guess we could plywood it in and then re-situate the pads/posts, by cross bracing..
    I heard that new foil bubble wrap stuff at SBS/Lowes worked good and could also be used as vapor barrier. Has any one tried it.
    I wish the previous owners had done it right to begin with, but thats what friends are for.
    Again, Thanks for taking the time to write...

  6. #6
    Supporting Member bullbuster's Avatar
    Join Date
    Oct 2006
    Location
    Mean streets of Fairview
    Posts
    1,140

    Default

    I put blue board insulation between the floor joists of my cabin. Works well and no critter problems in 15 years. It is easy to cut into managable sizes and is held up with nails toenailed in below the board.
    Live life and love it
    Love life and live it

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •