insulating under staple up radiant heat??

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by twilbanks, Jan 9, 2010.

  1. twilbanks

    twilbanks New Member

    Messages:
    5
    Location:
    IA
    Building a house and using stable up pex in the joist spaces (actually spaces b/t web joists) under the subfloor. This is under our upper level, with conditioned space below on the mainfloor and below that with a finsihed basement. Both the main floor and basement have pex embedded in concrete.
    My question is, will it be adequate to insulate b/t the joist spaces with R-11, leaving a 2-3" airspace under the tubing? Also, I bought craft faced (sp?) R-11, so do I put the paper down, toward the ceiling/conditioned space below? (I'm doing the insulation install to save $$$ rather than have the HVAC crew do it.) The finsihed floor above will be a mix of engineered wood and carpet with the special pad for radiant applications. We're using a gas high-efficiency boiler and my HVAC contractor says he will run the H20 at around 140 degrees.
  2. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Bubble wrap insulation first, shiny sid towards the floor with an air space then the r11. Or 1" styrofoam with an air gap.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,812
    Location:
    Cave Creek, Arizona
    insulation

    The paper is a vapor barrier and has absolutely no function between floors. You could purchase plain insulation without the barrier cheaper. It just presses into postion between the joists and stays there until you install the sheetrock. That is the way an insulation company would do it.
  4. twilbanks

    twilbanks New Member

    Messages:
    5
    Location:
    IA
    I got the paper-backed only b/c it was on sale and with a mail in rebate ended up being $4/roll cheaper! I figured besides being cheaper, it would be a little easier to work with.

    In regard to the foil bubble I've heard so many different opinions on whether it's necessary or not. It seems that most say it's not needed unless there is unconditioned space below, and that bat insulation is fine over conditioned space.

    Thoughts?
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,812
    Location:
    Cave Creek, Arizona
    foil

    When the vapor barrier is needed, it goes BETWEEN the heated room and the insulation to keep moisture out of it. Otherwise the vapor will get into the insulation and freeze in the wintertime, and possibly mildew in the summer.
  6. khali

    khali New Member

    Messages:
    5
    Location:
    Houston
    Try polyurea spray for insulating.It's water proof coating protects it.Many company providing polyurea spray for insulation and joints fill up.e.g ultimate linings,xtremeliners etc.
    Last edited: Apr 28, 2010
  7. ak_fangler

    ak_fangler New Member

    Messages:
    3
    Location:
    Alaska
    If the space below is semi-conditioned, like a garage, would the vapor barrier go above or below the insulation?
  8. leejosepho

    leejosepho DIY scratch-pad engineer

    If you want to be sure the heat goes up, the double bubble will help address that ... and I would shy away from paperback insulation between heated spaces.
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