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Radiant and Pavement

I searched the old posts but couldnt find anything. IS there a good place to get some info on putting radiant under black top or is this not doable.


  • it's doable, generally in a sand bed under the pavement. what kind of info are you looking for?

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  • My take on PEX & asphalt

    Asphalt is a difficult material to melt snow with and is not “widely recommended.” The high temperatures of the applied asphalt, combined with a resistance usually twice that of concrete, coupled with the later complication of what happens when a second or third layer is required, makes this a poor choice for snowmelt. IMO

    The temperature of asphalt laid directly over PEX tubing must NEVER exceed 240°F. If hotter asphalt is required, a lift of low temperature asphalt must be laid over the tubing first, followed by a second lift of higher temperature asphalt. To prevent damage to PEX tubing, it must be cooled while the asphalt is being laid. Before the asphalt is laid over the tubing, connect the supply manifold to a fresh water supply. Continuously run cold water through the tubing to dissipate heat from the asphalt. The water must be dumped from the return manifold to a drain or stored for future use. *Hundreds,,, upon hundreds of gallons may be required for this. A minimum of 40 psi must be maintained in the tubing during cooling. The maximum allowable pressure for cooling is 100 psi. The fluid temperature for PEX tubing buried in asphalt should not exceed 150°F.

    PEX and asphalt do not seem to mix well since they are both petroleum based products and the asphalt/PEX barrier will eventually break down and eat the PEX tubing over time. Burying tubing should be PERMANENT !!! This is besides the hot Temps. that asphalt must be laid down at. PEX embedded in a sand substrate, will prevent deterioration of the tubing but, many PEX Mfg’s. engineers have worked it out that there is way too much air in a sand or a dust bed (which acts as an insulation) to make it economically feasible.

    My suggestion to you is of course to use concrete and then lay the asphalt over the top if you must. But if you really want to embed PEX in the asphalt, I strongly recommend that you first talk to your PEX manufacturer of choice and get their opinions on this on paper.  If they agree to letting you install the snowmelt your way, get it from them IN WRITING and file it away. That way if the minds that I’ve talked to about this subject are wrong and it still causes a leak after a few years, you will have some back up to go after them with.

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  • Gordy
    Gordy Member Posts: 9,514

    Not to mention the operations with equipment laying the asphalt. Paver, Dump trucks,and rollers. Seems to me the hazards of just crushing or snagging the tubing is enough to abstain from doing it.
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542

    You stated "PEX and asphalt do not seem to mix well since they are both petroleum based products and the asphalt/PEX barrier will eventually break down and eat the PEX tubing over time."

    Got proof? Or is this conjecture. I was told that short of rocket fuel PEX can withstand just about anything...

    Inquiring minds want to know.

  • Mark,

    I certainly don’t intend to misinform. I’m assuming from your response that you have a whole bunch of working SIM panels out there that are embedded in asphalt and doing quite well.

    I don’t have any real physical proof of my assertions about PEX in asphalt because we’ve never attempted to experiment with it as I’m sure you have. I’m just passing on my advice that I’ve been given from sources I trust. The dialog above comes mostly from my communications with a couple of PEX tubing manufacturer’s technical representatives. Wouldn't they know what is best?

    In your experience, is this method desirable and permanent, acceptable, or merely a marginal method? Because if it’s desirable, It just might make selling snow melt much more attractive to the client.

    I really hope that rocket fuel isn't the only thing that breaks down PEX;-)

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  • Robert O'Connor_3
    Robert O'Connor_3 Member Posts: 272
    pex/ asphalt/concrete

    the asphalt does not adhere very well to concrete.
  • Tim Doran
    Tim Doran Member Posts: 208
    Different methods

    The cold lift method is used but not very common for obvious reasons. The most common method has insulation then a base of crush refine or crushed line stone, etc. Usually 2" to 3" thick with the tube embeded. The asphault is then layed on top. With 40-60 psi and cold water running through the tubing the weight of the paver and dump trucks is not a problem and the temps are exceptable.

    The conductivity of the materials is certainly less than a concrete system but the water temperature limitations are not there so it is possible to get good performance. I can model the diferent assemblies for anyone that is interested.

    Tim D.

  • Sam_8
    Sam_8 Member Posts: 1
    black top

    Given how much of an expense it is to install and use a radiantly heated driveway wouldn't it be better not to use such a shortly lived product? Asphalt's life expectancy is relatively low in my experience. The stuff gets realy soft in the summer and unless you keep a good coat of sealer on it, it tends to come apart rather easily after 5 years or so in my experience. Moisture gets under really easily and it's subject to frost heaves. Not a good thing when pipes are in there.

    I'd say it can be done but why bother? If the pipes are below in a bed of sand or crushed rock, the surface can be replaced but I wouldn't want to risk damage to the tubing if it were me.

    The thermal conducivity ism also much lower than concrete.
  • Paul Mitchell_2
    Paul Mitchell_2 Member Posts: 184

    I appreciate all the responses. I am torn on what to do. I would love to do concrete. And I might still. I know this is the best for PEX. I do know that the concrete is much more expensive if someone does it for me. I also need to excavate some extra dirt to double wide my drive. Tough to get a mason around here...let alone a good one. I have to get some more prices, I do know that if the concrete is done right it will be here for 30 years+. Done right is the key.
  • Paul Mitchell_2
    Paul Mitchell_2 Member Posts: 184

    What is the differance in energy consumption to melt snow? I have oil heat. Would it cost say...double if there was blacktop over the radiant as compared to concrete?
This discussion has been closed.