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Snowmelt in Gravel? ME

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G.Kaske_2
G.Kaske_2 Member Posts: 30
Hey ME I won't get into the snowmelt end of this but the base sounds like a maintenance nightmare. Thinking freeze thaw cycles, and why they post roads, thats with a solid surface.

I think you need to pursue traffic loads, Drainage to take moisture away from the subbase. Once the subbase gets saturated, probably from the edges in being the foam will shed the water. You could get areas of pumping subbase which could pump the tubing out of the ground.


I inserted a paint sketch of a general drainage idea if you are going to give it a whirl.

If you can't create a drainage ditch on each side due to site conditions I think you should abandon the idea. Thinking long term product reliability.


Gordy

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  • Rob Blair
    Rob Blair Member Posts: 227
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    Snowmelt in Gravel? ME

    Looking at a 1300 square feet snowmelt job where the homeowner wants gravel in the drive. What is proposed is 2" Dow Insulation, 3/4" tubing covered with 2" of compacted stone dust, a layer of filter fabric, 2" of 2-B modidfied compacted, then this material called Gravel Pave 2, which will hold appoximately 2" of White Granite Chips. I am in Pittsburgh. Has anyone tried anything like this before?

    Rob
  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,291
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    Never attempted anything like that

    I would think that rain, sleet, slush, snow soaking into and then draining out of the porous gravel mix would be a major additional load factor. A WAG would be figure your normal load and multiply by 1.6. Probably have to be installed as a Class 3 in order to perform as a Class 1.
  • ALH_4
    ALH_4 Member Posts: 1,790
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    snowmelt

    Rob, I think I would insist on the tube being embedded in something solid. I could see a large vehicle or particularly wet conditions causing damage pretty easily.
  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,291
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    Good thought Andrew

    I was thinking of the system performance aspect only.
  • Rob Blair
    Rob Blair Member Posts: 227
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    That is the idea of the stone dust with the fabric between it and the compacted modified. When you compact that stone dust it gets hard as rock. Originally they wanted sand, but I thought that the stone dust would become a better transfer medium. Believe me, there are lots of concerns on this job. Working with the architect, so I am sure alot of you can relate.

    Rob
  • jp_2
    jp_2 Member Posts: 1,935
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    if they can

    afford snowmelt and the associated costs why can't they afford a solid surface?

    better yet, why can't the guy use a snowblower?

    I'm going to tell AL Gore on you :)

    ADDED:

    It may actually work Ok, when wet the heat will travel through the liquid, far better than triing to heat the dry gravel.
  • Weezbo
    Weezbo Member Posts: 6,232
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    nope. however...

    Yes i Have been called to trouble shoot and find the leaks in a similar driveway.

    Like Andrew i would mentioned "washed" cement.. with the granite swept and washed for the surface...that way it is in something solid and it has the esthetics of the granite...
  • hot_rod
    hot_rod Member Posts: 22,157
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    sounds like a boat to me

    get enough water under that foam and off to the neighbors.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
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    At first it sounded a bit foolish but the more I think, the more I believe it will work fine.

    Think about it. When you melt snow from a hard surface you loose a huge amount of energy when the snow you have melted runs off.

    Specific heat (roughly the ability of a substance to hold energy in the form of heat) of concrete is "iffy" but somewhere around 0.88. Remember--water has a specific heat of 1.0 which is significantly higher than most common substances.

    If instead of just running off a significant amount of water is retained in the bed (filling in the gaps), you wind up with even more energy available for melting than with concrete or stone.

    Since liquid water actually starts getting larger as it approaches freezing (it's smallest at 38F or therabouts?), the newly melted snow should actually flow run off once the bed is full.

    Sounds like good insulation and a good bed to protect the tube. I can't see a problem--and it might even work better than concrete.
  • ALH_4
    ALH_4 Member Posts: 1,790
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    Until the stone is saturated, I think the conductivity would be quite low. I still question whether saturated compacted stone is structurally sound enough to protect pex tube beneath a 2-ton vehicle.

    How about trying to dry that saturated stone? It is certainly better for that moisture to run off than having to evaporate all of it. There could be problems with heaving and re-melting any ice left in the stone could use quite a bit of fuel. Where do you put the Tekmar 090?

    It sounds too risky to me. There are just too many ways for this system to fail, thermally or structurally.
  • mtfallsmikey
    mtfallsmikey Member Posts: 765
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    Not to mention

    What if there is a system failure and the HO calls in a snow plow? Anything is possible!
  • Mad Dog_2
    Mad Dog_2 Member Posts: 6,947
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    Absolutely Andrew......

    Thats the first thing I thought of...even washout and exposure of the tubing. Mad Dog

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  • Mad Dog_2
    Mad Dog_2 Member Posts: 6,947
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    Absolutely Andrew

    That was my first concern: washout and possible exposure of the tubing that could lead to damage. If you insulate and have the btus that would melt snow and ice, not as efficiently as a monolithic slab would of course. I would INSIST on atleast a protective depth slab (3"????) Mad Dog

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  • G.Kaske_2
    G.Kaske_2 Member Posts: 30
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    Mad Dog

    I agree but if your going to do that may as well pour another 1 or 2". Turn it gray.

    Gordy
  • Weezbo
    Weezbo Member Posts: 6,232
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    Do any of you have that jpeg of the driveways that a hummvie

    would but a nut at? that was 'hill'arious:)
  • boilerpro_4
    boilerpro_4 Member Posts: 12
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    Rob, Yes, I have tried this and I was not really happy with the results. The energy consumption is huge and the stone sticking up with the top and sides exposed do not trasfer heat as you would want.
This discussion has been closed.