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sand for heat tranfer media?

pipekingpipeking Posts: 252Member
 a buddy of mine is building his home and it's a log cabin, but huge. anyway, he is always asking for advice, but never want help with the labor. he usually finds my insight really helpful and takes it, but he came up with the idea of using sand to enhance the heat transfer of his sleeper radiant system. it kind of sounds like a good idea, but i never heard of it, has any of u guys done this?
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Comments

  • Jean-David BeyerJean-David Beyer Posts: 2,470Member ✭✭✭
    using sand to enhance the heat transfer of his sleeper radiant system

    I am not a heating professional, but it sounds like a terrible idea to me. Perhaps a little better than styrofoam as a heat transfer medium, but not lots better.



    Why not use aluminium heat transfer plates instead. Instead of insulating the tubing from the bottom of the floor with air or sand, the heat would be conducted directly to the wood of the floor.





    My spell-checker seems to be using a British dictionary. When I write color and aluminum, they are flagged, but colour and aluminium go right through.
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  • GordyGordy Posts: 3,740Member ✭✭✭✭
    edited March 2013
    Bad idea

    Lots of people come here with that idea as a good one.



    Not only is sand a better insulator than a conductor. Think air pockets between sand particles. It also will harbor insects especially ants. Not only brought in with the sand but on site as well.



    Next time your at a beach and the sand is so hot you can't hardly walk on it not far down is relief a few inches at most.



    Not really sure how sand could be implemented in a typical over the top sandwich /sleeper assembly for radiant. Usually it's plates, or no plates then finished floor, or some kind of backer for tile etc. or glpcrete with nailers poured in for hardwood finish floor.
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  • pipekingpipeking Posts: 252Member
    what he did

    was staple down the tubing to the floor 6"OC with sleeper 2x4 in between, then poured sand on top of the tubing. he had that expanding spray insulation under the sub floor in between the joists. my first reaction to this was a bad idea, cuz of the air in the sand, so  he used a hi density sand and his argument was, it is  like having stone (or concrete) a hi thermal mass. i wish i had a FLIR!
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  • GordyGordy Posts: 3,740Member ✭✭✭✭
    Type of sand

    Does not matter much unless he is going to use cement, and water turn it into mortar..



    Really all he accomplished is turned a potentially quick responding possible low mass radiant assembly, and turned it into a higher mass slower responding radiant assembly. It will work and the sand is really not helping anything except a filler.



    If you want to really get him thinking give him ant traps for a house warming gift. Hopefully the carpenter ants do not move in they may like the log home residence.





    Ask me how I know.... I did a stamped concrete patio in my court yard out in front of the house. We used ag lime on top of the 6" slab that was there with a flagstone mortar assembly. Removed the 3" of flag stone and mortar bed installed 2" of ag lime as a bond breaker pored 4" of concrete on top. Guess what came with the ag lime.... Ants lots of ants. Never noticed any while doing it but they. Are all over now.

    Ag lime is very fine crushed lime stone almost sand consistency that gets rock hard with a little water, and a plate compactor.



    My other home a rental is radiant slab on grade done in the 50's. they used sand as fill / insulator to the ground. Guess what's a constant battle there... Ants. They love sand.
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  • pipekingpipeking Posts: 252Member
    that's what i was looking for....

    there had to be a major downside to this. ant farm!lol! thanks
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