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Insulation under Uponor Joist Trak radiant

We replaced all the steam radiators on our first floor with a Uponor radiant Joist Track system in 2010 and it has been a wonderful improvement. Now, however, the mice have made a mess of the fiberglass batting that insulates the basement ceiling and the radiant pipes/plates and is coming down in places. If we could eliminate all mice, we would, but that's impossible with a 17th c fieldstone foundation, alas.

Seems like our choices are: 1) redo the fiberglass, knowing it won't be the last time, 2) use rock wool instead of fiberglass (is it any less attractive to mice?), or 3) use spray foam. Uponor's tech support suggested spray foam.

I understand this is a conductive heat application, i.e. we don't want an air gap under the hydroponic PEX -- so spray foam seems like a potential and durable solution.

Are there any downsides to using spray foam?


  • GGross
    GGross Member Posts: 703
    edited September 19
    Here is an important document regarding spray foam and Uponor products. I am not too familiar with spray foam myself, maybe someone else can chime in regarding this document. I know it came up a few years ago on a new construction project but I can't recall the specifics of that job

    Basically the pipe is fine to spray foam if done correctly, the fittings need a wrap

  • hot_rod
    hot_rod Member Posts: 19,954
    I would put a 3/4 0r 1" foamboard against the track first. I have seen the foam squeeze in between the plate and subfloor. That foam finds every crack and expands into it. So you lose a bit of your conduction transfer.

    Or maybe just tape along the edges of the plates to keep the foam out?

    The spray foam will do a great job of sealing for infiltration and gluing your entire joist assembly together.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • DyedInTheWool
    DyedInTheWool Member Posts: 21
    Thank you both so much for weighing in! Lots to read and consider. Appreciate it!
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,141
    edited September 20
    I used spray foam on my Brigantine, NJ home's radiant tubing. The addition was slab on grade and that is the best heat EVER! The rest of the home was over a crawlspace. So I used aluminum plates and had the spray foam guys in after the pressure test was successful for 1 month. Not as good as the slab, but it works great. I would recommend the spray foam.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • kcopp
    kcopp Member Posts: 4,262
    I did a job 10+ yrs ago similar to this.
    We used corrugated cardboard 8' sheets, folded along the edges, stapled them to the sides, pressed up against the tubing and plates. No air space.
    Spray foam was done over the top.
    Its been great.
  • DyedInTheWool
    DyedInTheWool Member Posts: 21
    Thank you all for the fantastic advice! I will start interviewing spray foam companies -- this is very helpful info in assessing their expertise.