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HePEX expansion noise or use Pex-Al-Pex?

JunkMonger Member Posts: 6
I'm working on designing a sandwich (insulated joist space, subfloor, grooved foam w/stamped Al transfer plates+1/2' tubing, underlayment, engineered floating wood floor/some tile) radiant system for an 1800 sq ft 2 story with 10 individual zones.

I'm trying to decide on pex options and was looking for opinions of HePEX barrier pex vs (any brand) Pex-Al-Pex in terms of noise or any other ideas. The HePEX is going to expand and contract much more than Pex-Al and I'm concerned that will translate into noise. I'm not concerned about any price differences.

The longest straight-line runs would be ~25 feet and it would be a relatively low 120 SWT on a design day (Coastal CA, 38 degree design) and an outdoor reset so realistically looking more along the lines of 110 SWT or less.

I know the "for every 10 F of temperature change, the length of PEX changes by 1 inch/100 feet of piping" but wonder how that relates to the real-world of when to expect noise and when not to. I've read HePEX is 'slicker' than some other brands and that helps. Is there any rule of thumb here? I've read avoid long straight runs so the expansion can be 'dissipated' in turns/expansion loops but don't know what that length is.

I'm leaning towards HePEX because I can't seem to find any particularly reputable brands of Pex-AL and worry about long-term de-lamination issues as the pex layers still want to expand at their rate and counting in the bond to the aluminum to restrict it.

Hit me with your wisdom!


  • Jamie Hall
    Jamie Hall Member Posts: 23,657
    The main thing with either type of tubing is to give it room at the turns to expand quite freely, and to avoid getting anything into the grooves which it is laid in which might try to inhibit the expansion. It's going to expand whether you want it to or not, and if anything gets in the way it will be noisy.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 22,483
    The tube really should not move in the aluminum plates.  Use a brand that has a tight grab on the tube. Do not fasten the end of the loops so movement can occur there.
    Any of the brand name he-Pex should work, stay with one that has a coating over the EVOH barrier. The hard, high gloss coatings tend to make noise.
    Go with an A Pex for best flexibility 
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    EBEBRATT-Ed Member Posts: 15,840
    if the pex expands 1"/100 feet with a 10 degree rise and your rise is 40 degrees, your longest run is 25' then you expansion is 4" x.25 or 1" total.

    Shouldn't be an issue
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,107
    edited July 2022
    We have used the Uponor hePEX and Mr. PEX on plate systems that both have the soft coating and both ‘tick’ minimally on start up. The owners say they have gotten used to the sound; comforting to know that the heat is on. 

    Have you looked at Ultra-Fin?  It has a few advantages: only one run per bay, water temperatures can exceed 120F without damaging hardwood floors and no expansion noises. Ideal for 2 x 8 joist bays or larger because of the insulation requirements. 
    Sold at Power Boiler Sales in Richmond. 
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • hot_rod
    hot_rod Member Posts: 22,483
    Possibly the sound of the aluminum expanding? Like aluminum siding in a house🥴
    The barrier noise is more of a squeak, like when you carry a loose roll if Pex and it rubs on itself.

    ODR and low SWT should get you a quiet system.

    Use the tight fitting plates and screw them tightly to the sub floor

    For low load systems  UltraFin is another option. It may require higher SWT as it is a convection not conduction energy transfer 
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • JunkMonger
    JunkMonger Member Posts: 6
    Thank you all for the feedback to help me realize I was making a mountain out of a molehill, for my system.

    Radiant making noise is not something I've seen discussed much on here except some of the more extreme threads where it was keeping people from sleeping so obviously my mind can only wander to the most extreme!

    I'm leaning towards Uponor HePex because I've dealt with PexB potable and it was a less-than-fun experience.
    I have always assumed the 'omega' shaped transfer plates would be better than the 'u' shaped ones so I'm glad to hear confirmation on that!

    I haven't really considered ultra-fin, mostly because I already picked up 2000 sq ft of the grooved foam on the cheap. Also, it likely wouldn't work as my first floor is 4x6 joists so not much room and I'm not keen on mixing systems if I don't have to.
    Alan (California Radiant) Forbes
  • Paul Pollets
    Paul Pollets Member Posts: 3,658
    Putting the zone on a motorized 3 way or 4 way valve will also greatly reduce noise or eliminate it. The modulated water temps won't slug the Pex with hot water on startup, when the pump is wired for continuous circulation.
  • ewang
    ewang Member Posts: 77
    I used HePex and omega plates from supplyhouse and ebay. Only makes some noise during startup and shutdown. Otherwise, I have mine on a constant circ with a nightime setback. No noise during the day.
  • SENWiEco
    SENWiEco Member Posts: 163
    Late to the party, but will provide my experiences. I used Uponor hePex and ThermoFin U plates. I did not leave any room for expansion based on advise from R.D.&S. loop ends utilized R.D.&S. manufactured return bends. Year 1 - no noise whatsoever. Year 2 - some clicking when significant change to supply water temp (after extended off cycle or switching between heating and cooling). Now into third year, and yes we get a series of clicks across the panel from time to time. It is not loud and only happens at beginning of an 'on' cycle, and only once per individual loop (you can hear it going from one end of panel to the other). I am the only one that notices, others in house have not mentioned. It is not at all bothersome, loud, noticeable for most, and like @Alan (California Radiant) Forbes mentions, it gives me comfort knowing the system is active.
    Sean Wiens