1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)

RADIANT FLOOR JOIST INSULATION

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by 91LMS, Oct 29, 2012.

  1. 91LMS

    91LMS Member

    Joined:
    Oct 20, 2011
    Messages:
    217
    Loc:
    MAINE

    Helpful Sponsor Ads!





  2. Fred61

    Fred61 Minister of Fire

    Joined:
    Nov 26, 2008
    Messages:
    1,767
    Loc:
    Southeastern Vt.
    I guess it works well for the reflection qualities and I believe in the need for a reflective surface but I've heard that it doesn't measure up to fiberglass blanket insulation.
  3. 91LMS

    91LMS Member

    Joined:
    Oct 20, 2011
    Messages:
    217
    Loc:
    MAINE
    they claim its r21 if its doubled up. wonder if i would see a differance with how much heat is driven up through the floor with fiberglass as apposed to the refectix?
  4. peakbagger

    peakbagger Minister of Fire

    Joined:
    Jul 11, 2008
    Messages:
    1,717
    Loc:
    Northern NH
    It may work fro your purposes but their R value claims have been debunked numerous times
  5. DaveBP

    DaveBP Minister of Fire

    Joined:
    May 25, 2008
    Messages:
    1,069
    Loc:
    SW Maine
    And remember that reflective surfaces only work as long as they remain dust free. I don't see many horizontal surfaces that remain dust free for long. Anywhere.

    I hate installing fiberglass overhead but at least fiberglass (and foam) don't rely on miracle effects.
  6. maple1

    maple1 Minister of Fire

    Joined:
    Sep 15, 2011
    Messages:
    4,238
    Loc:
    Nova Scotia
    Hmm, I got some of this stuff this weekend to try covering the Roxul tied around my storage tanks. I wasn't counting on it for a lot of insulating value though.
  7. charly

    charly Guest

    I used the foil bubble sheets on our radiant install as well. Had it at the bottom of the joists. Worked fine for us , but was told a better install would be to keep it an inch or so away from the tubes instead of heating the whole joist area. We had 12 inch wide knotty pine floors , Advantec sub-flooring and it worked fine. I thought this was a pretty straight forward site to answer some radiant questions. radiantdesigninstitute.com
  8. Hollow Pine

    Hollow Pine New Member

    Joined:
    Oct 24, 2012
    Messages:
    4
    Loc:
    Central Maine
    My heat guy had me lay radiant foil shiny side up on top of the 3.5" fiberglass that we stapled to the bottom of the floor joists, We used the ultrafin system so my tubing hangs about 3' below the subfloor in what is essentially a dead air space. The foil and insulation is another 3 or so inches below that.

    Jeff_L
  9. 91LMS

    91LMS Member

    Joined:
    Oct 20, 2011
    Messages:
    217
    Loc:
    MAINE
    interesting jeff l. my system is of the same design with 12" joists. i am just concerned trying to push heat through my advantec and 3/4 oak floor. hoping that 3.5" of insulation is sufficient and thinking that a reflective layer should be there to help my cause. i agree with the dust thing but the pockets should be sealed so hoping the dust will be minimized.
  10. JP11

    JP11 Minister of Fire

    Joined:
    May 15, 2011
    Messages:
    1,238
    Loc:
    Central Maine
    I used the foil faced hard foam. 2"

    I left one inch of air space between the pipes and the foam. I'm going thru advantek, mortar, ditra, mortar and tile.

    No reflector plates, tubes just stapled to subfloor. Works good.
  11. 91LMS

    91LMS Member

    Joined:
    Oct 20, 2011
    Messages:
    217
    Loc:
    MAINE
    is that foam foil faced on both sides jp? that was my first thought but at 40 bucks a sheet i was doing more research
  12. JP11

    JP11 Minister of Fire

    Joined:
    May 15, 2011
    Messages:
    1,238
    Loc:
    Central Maine
    yes. I don't remember it being that pricey. I was slicing roughly 22" x 8' sheets.. and sticking them up in floor trusses. a few toe nails to hold them. If you cut them right.. they pretty much just stick in from pushing them in.
  13. 91LMS

    91LMS Member

    Joined:
    Oct 20, 2011
    Messages:
    217
    Loc:
    MAINE
    even easier in my case jp where i have engineered joists. depot was the cheapest so far on the foamular. the reflectix with fiberglass is less money than foam. mainly want functionability over price, should be forever if its right.
  14. davidsutton

    davidsutton New Member

    Joined:
    Nov 3, 2011
    Messages:
    2
    Loc:
    kalamazoo mi
    I put 1/4" foil faced foam (cut to fit fan/fold) from menards foil side up towards screwed up pex tubing (pex spaced off bottom of floor 1.5") and then r13 under that. It is working like charm through a sand which of flooring ( 3/4" tongue and groove sub-floor, 1" hardwood original floors and on top of all that the new 1/2" floating wood floors). Also working great upstairs through 2 layers of sub-floor and then stain-masters rubber carpet pad for radiant and new plush carpet. It is cheap and works well. I did every floor in my house is this way. Just my 2 cents.

Share This Page