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question on radiant

maine rick
maine rick Member Posts: 107
PEX IS ALREADY DONE AND FLOOR FINNISHED I'M DOING THE BOILER INSTALL AND WAS TALKING WITH THE OWNER ABOUT IT. SHOULD BE TAKING PIC'S NEXT WEEK ON THE PIPING AND SET UP NOT FANCY TRYING TO KEEP COST DOWN AND DO A GOOD JOB OWNER IS VERY HAPPY SO FAR.

Comments

  • maine rick
    maine rick Member Posts: 107
    basement radiant

    whats best radiant pipe floating in slab or left on top off insalation? 4" slab will it be better to try to get pex around 2" or leave it at 4" any pro's or con's.
    thanks
  • Ericjeeper
    Ericjeeper Member Posts: 179
    make sure it is completely encased in concrete

    If you do not set it on chairs or make sure your finishers pull it up into the slab... you might not be getting the most out of your tubing. if it is laying trapped on the bottom only touching concrete on the top and sides..... You might not get as good of rub off as if it were encased mid way up into the pour. Some claim that closer to the top will result in a quicker warm up. just my .02
  • John_82
    John_82 Member Posts: 63


    Insulation, then rebar or wire mesh, tubing gets strapped to that, then concrete on top of the whole thing. The insulation has a white reflective surface, so it shoots the heat up. works great!
  • i use

    pipe tracking attached to styro, keeps pipe about 1/4" up above said styro into concrete. then mesh is thrown on top, which makes for a stronger slab it would seem to me.
  • hr
    hr Member Posts: 6,106
    In a perfect radiant world

    the tube would be several inches below the top. Remember ACI recommends 3 times the aggregrate diameter above rebar or tube. So 3/4" minus rock in the concrete would require a 2-1/4" layer above the top of the tube. So in a 4" slab that would be about 1" above the insulation.

    Also keep in mind most concrete installers saw control joints these days. They like 1/3 the thickness of the slab for a cut depth. Although not all read a tape measure that well!

    I'll tell you getting, and keeping the tube just 1" above the insulation is easier said than done. With welded wire I have placed chairs as close as 2 foot on center and the tube and mesh still sags between. I'm not convinced there is any absolute way to keep the tube up. Rebar with chairs and the tube tied every 1 foot or so may work??

    If you ask the concrete installers to hook and lift the tube, and they happen to be pumping the mud, count on some floaters! Or some very thin concrete over the tube. The force of that mud hitting the insulation will tend to over lift the tube.

    Actually I see more and more contractors (in magazine articles) stapling the tube to the foam. This takes the costly, cumbersome wire mesh out of the installation,which concrete finishers hate and poses a wear and poke issue for the tube.

    Also a few foam manufactures are making a foam with tube grooves or positioners built in. Again at the very bottom of the pour however.

    This article will show you what that additional depth will cost in performance an/ or additional supply temperature.

    http://www.pmmag.com/CDA/Archives/67c66155b6fc7010VgnVCM100000f932a8c0____

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