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Best pipe for in floor radiant (joist bay install with Ultrafins and cold expansion fittings)?

watercourse Member Posts: 28
edited January 2023 in Radiant Heating
What are your top picks for in floor radiant, with pipe going in between joist bays, and using Ultrafins to spread the love?

Looking for pipe that is...
  • quiet
  • flexible
  • good with cold expansion fittings
  • durable
Looking forward to your recommendations, thanks!


  • GGross
    GGross Member Posts: 1,105
    There is no such thing as quiet pipe, it's all about how it is installed and operated! That being said Uponor is the clear winner for cold expansion connections
  • Ironman
    Ironman Member Posts: 7,399
    What type of boiler are you using? A mod/con or a cast iron atmospheric?

    Running the high SWT needed for Ultra Fin (180*) will cause pex to greatly expand and act like spaghetti. You’ll need a lot supports and allowance for that.

    Pex-Al-Pex has minimal expansion and is a much better choice for a high temp application.

    If you have a mod/con boiler, then I’d use heat transfer plates instead of Ultra Fin where you could run a much lower SWT and have a more efficient system.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • hot_rod
    hot_rod Member Posts: 22,483
    First what are the heat loads of the rooms? UF can work at much lower temperatures then 140, if the load is reasonable.

    Any of the A type pex will work, properly installed. Rehau, Mr Pex, Uponor.

    PERT seems to be another flexible tube option, I've never run it myself.

    PAP is not a very friendly DIY tube for joist bay work.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • watercourse
    watercourse Member Posts: 28
    Thanks for all your answers here. After much shopping around I'm going to try Vipert, PE-RT that is compatible with cold expansion.