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Under slab insulation

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marc
marc Member Posts: 203
in THE MAIN WALL
There will be complete R-10 vertical edge and under slab insulation.

Marc

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  • marc
    marc Member Posts: 203
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    Under slab insulation

    Builder inquired about the location of the R-10 insulation in relationship to the slab. He would like to install the horizontal insulation +/- 30" below the slab, in lieu of directly under the slab. Do you think it will effect the heating system in anyway? I think that at start up in the fall there might be a longer "lag" time until the room gets to the target temperature.

    Thanks,

    Marc
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
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    I believe your on target

    The purpose of the insulation is to minimize heat transfer in a given direction. By putting the insulation so deep, you are allowing the heat energy in the slab to be readily absorbed by 30" of some dense medium - I'm assuming dirt.

    Every time you want to heat or cool that slab, the response time will be extremely long. In fact, I would venture to say, it would react as if there were no insulation at all.

    In my opinion, the insulation should be directly under the slab to minimize the absorbtion of heat energy to the earth. In addition, your should have edge insulation for the slab to prevent heat energy from conducting out the sides.
  • Unknown
    Unknown
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    +/- 30\" below slab?

    What`s that gonna do for your comfort? Warming the fill in between. Do you want to pay fuel bills to heat dirt?

    Dave
  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124
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    why does he...

    want it so low? I agree that this is not a great plan..if the sub soil is prepared properly the strofoam should support most any weight under that would be on the slab...kpc

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  • hot_rod
    hot_rod Member Posts: 22,158
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    It would depend

    on how well the fill material conducts heat. A backfill of all pea gravel for instance would be a poor conductor. Dirt or clay a better conductor. Moisture content also wouyld be part of the equasion. A complex thing to model I'm told.

    Regardless I would still keep the insulation layer under the slab pour. It's a hrd thing to correct if done improperly :)

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
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