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Calk/adhesive with a high thermal conductivity

ClevelandOhio | Posted in General Questions on

I am looking for something that I can load in my caulk gun or apply with a brush on the aluminum panels for radiant floor heat.

I found this, but the price point is too high:

Maybe someone knows of a common glue/caulk that just so happen to have high thermal condutivity?


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  1. Expert Member
    BILL WICHERS | | #1

    Thermal conductivity is a function of thickness of the material, so you want to make sure you keep the layer of whatever adhesive material you use as thin as possible.

    Regular silicone is decent in terms of thermal conductivity when compared to some other materials, but none are great. I’d be more concerned with silicones ability to handle the heat better though — some other materials are likely to get brittle over time in an application like this.

    Are you sure you’re not overthinking this a little? Usually these systems don’t need adhesives.


    1. ClevelandOhio | | #2


      Thanks for your reply!

      You are absolutely right... on all counts.
      I think recently installers started using adhesives to fill the voids between aluminum and wood. It fills the gaps.

      I am stapling to a pretty rough wood, so I thought it would be nice to get a better contact between surfaces.

      Here is another option I found: I wonder if I need flexibility for the expanding and shrinking materials... What do you think?

      Or maybe I can use heatsink compound like the paste that is used between a microchip and its heatsink.

      1. Expert Member
        BILL WICHERS | | #4

        Potting compounds are usually hard and rigid. They are normally used to encapsulate electronic circuitry to protect the components from vibration, or to weatherproof them.

        Don’t use heatsink grease. It will probably soak into the wood and leave the interface area so it won’t accomplish anything. Also, radiant heating systems don’t operate anywhere near the energy densities of semiconductors. A typical microprocessor these days might be dissipating 90 watts in about one square centimeter. Your radiant heating system is probably running more around 9 watts per square foot — that’s about 9,290 times lower energy density for the radiant heating system! High thermal conductivity interface materials are not necessary in your application.

        Personally I wouldn’t worry about it. Just mount the plates to the wood and be done. Filling little air voids in the grain of the wood is unlikely to make any noticeable difference. The wood is already a thermal insulator, so you’re not accomplishing much. I’d compare this to trying to install a radiant heating system on a fiberglass insulated wall, and trying to paint the fiberglass first to “fill the gaps” between glass fibers on the surface. Sure, not a very realistic application, but good for the purposes of making an analogy here.


  2. Jon_R | | #3

    Anything (including silicon caulk) will be much better than air.

  3. ClevelandOhio | | #5


    You have very detailed knowledge in this area!

    Your analogy has put things into perspective for me -- so I am trowing in the towel and setting the price point of this adhesive to $0.



    1. Expert Member
      BILL WICHERS | | #6

      See, look how much money you saved! And time too. One must always resist the temptation to overengineer things, similar to “feature creep” (the tendency to add more features and delay the release date) in product design.

      I’m an electrical engineer with a background in RF/microwave systems design where big aluminum heatsinks and copper heat spreaders (needed because aluminum isn’t a good enough thermal conductor) are used with high-power semiconductors in amplifiers. I don’t do that professionally anymore — I consult on critical facilities systems designs now —, but sometimes the heatsink knowledge comes in handy for other things :-)


  4. ClevelandOhio | | #7

    I love RF.

    You rock!

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