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Insulation in crawl space

ArnoldT
ArnoldT Member Posts: 4
in Strictly Steam
I'm having a radiant system installed under a floor of a crawl space that has a dirt floor. Using aluminum transfer plates and would like some recommendations for insulation when the work is finished. Room is 15 feet by 23 feet. All wood floors and joists. Knee wall is old brownstone irregular block with two small windows. Thanks a bunch
melvinmelvin

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,983
    I would think spray foam if it is rated for the radiant floor temp. I am not sure. If you use fiberglass the mice will have a field day playing up there and it is hard to keep them out
    SlamDunk
  • Jamie Hall
    Jamie Hall Member Posts: 23,957
    Not only will the mice have a ball, but fiberglass WILL get soggy and generally a mess. Spray foam if you can, otherwise rigid foam carefully fitted and with a vapuor barrier on the WARM side.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ArnoldT
    ArnoldT Member Posts: 4
    Thanks for the input. If I spray foam up on the PEX tubing how would get to it if there's a leak. I've been told to put either fiberglass or rock wool up against the PEX leaves a 2 inch gap to act as a heat sink. The foundation walls are stone and any suggestions about insulating them?

  • Jamie Hall
    Jamie Hall Member Posts: 23,957
    You do have a point with the spray foam -- I think I'd be inclined to use rigid foam under the joists, with a vapour barrier. And don't, please don't, use either rock wool (although that's a little better) or fiberglass in a crawl space. It will get moisture soaked and be a nice haven for all kinds of critters with four and six and more legs. Just don't do it.

    You can spray foam the stone walls.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • melvinmelvin
    melvinmelvin Member Posts: 11
    Is the crawlspace vented or invented? What climate zone (IECC) is the home located in?
  • ScottSecor
    ScottSecor Member Posts: 873
    This may work in your situation.   Install Rockwood I situation with a two inch void below the subfloor (6" insulation for 8" joists.  When finished amd tested for a week or so, add 1/2" or 1" ridgid foam insulation below,  nail or screw to the bottom of the joists. 

    As far as the exterior walls, maybe rigid foam panels, gkud to the stone walls?
  • ArnoldT
    ArnoldT Member Posts: 4
    Melvinmelvin:

    Home is in Northern New Jersey, two miles west of the GW Bridge. Looks like Climate Zone 5.

    Crawl space is un-vented.
  • PC7060
    PC7060 Member Posts: 1,279
    edited December 2022
    XPS panels work well for exterior masonry walls.  Be aware that foam must be covered with an approved ignition barrier unless it has been specifically tested and certified as not requiring an ignition barrier.  

    Dow (now DuPont) offers the only foam panels I know that’s approved for basements and crawlspaces without an ignition barrier at thickness up to 2”.  
    Hear the link to the report.  Seems to be a lot of conditions for use in crawl spaces as well. 

     https://icc-es.org/wp-content/uploads/report-directory/ESR-2142.pdf

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