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Onix plateless vs. pex w/plates

Andrew Hagen_2
Andrew Hagen_2 Member Posts: 236
I definitely recommend against EPDM tubing in a heating system. The aluminum barrier in Onix is actually something of a mylar film from what I can tell. I am sure we have all seen mylar helium balloons lose their buoyancy.

I would question how the pex with plates guy is installing the plates and tube. The plates are most quickly installed with a pneumatic roofing nailer with 3/4" nails or a 16ga stapler. The tubing is most quickly installed with a Danair pneumatic palm hammer. Under floor is harder on the neck and shoulders, but saves your knees.

Pex-Aluminum-Pex can be used in plates, but it is difficult to pull through the joists. With regular pex, there could be some very faint ticking noises at startup, but if outdoor reset is used, the temperature swings are greatly minimized.

Comments

  • rogGoarfsoony
    rogGoarfsoony Member Posts: 8
    Onix plateless vs. pex w/plates



    Renovation Pro here - looking to have radiant/solar/mod con boiler system put in. I just read the thread about black gunk in watts onix for radiant heating. Is pex the way to go for staple up? How can I minimize or reduce $thousands on extruded heat plates? How do I minimize the effects of pex expansion and difficulty of installation of that tubing? Any Ideas would be appreciated. thanks!

    Need Help! Watts Onix .vs. Pex w/plates for Staple up Radiant/Hydronic Heat
    Thanks for any input on pex vs. onix and plates vs. plateless...

    I'm a renovation pro looking at several hydronic heating subcontractors for my radiant heating job (in my residence) in Northern Virginia on a 1920's house with new addition. Planning to be here 25 yrs or more. I'm using spray foam and working hard to upgrade the whole building envelope. Both hydronic subs have recommended the Triangle Tube Prestige Solo modulating condensing high-efficiency wall mount boiler - so that seems to be set.

    One is suggesting Watts Onix as the staple up tubing - preferring the more flexible and durable tubing for easier install, the tighter bending radius (ability to double it up at exterior walls in the old less insulated part of the house), and the ability to put higher temp. water through it and have it transfer to the floors without aluminum heat plates. The onix is a lot more $ than the pex - but perhaps we won't need the extruded plates with the onix?

    The other is advocating pex with an oxygen barrier, and extruded plates (very $$). From what I can determine pex is less durable vs. onix (according to other sub and Watts claims), can kink, and has a lot more expansion that can cause problems, noise, etc. But it's 4-5 times as expensive as pex with Al. oxygen barrier.

    Both subs recommend a 1" air gap below the staple up with a reflective layer and insulation below that to force the heat up into the floors. (all staple up bays are over heated space and the band joist will be spray foamed so the heat won't be lost to outside.

    At design temps the plateless onix will have to have a higher water temp to get the BTU's to the room - 140 degrees - vs. lower for pex with plates. This will result in a higher water temp on the return to the Triangle Tube resulting in less condensing and lower than rated efficiencies. But the onix will be quieter with less expansion and easier to install and double up at the exterior old house walls. Seems like the cost of onix vs. pex with plates will be roughly a wash - so I'm stuck on which way to go.

    help!
  • Mark Custis
    Mark Custis Member Posts: 539
    Both systems in service

    Staple up is a pain. Just hard work no matter what material one uses, (my aged left shoulder may be tainting my opinion).

    My new favorite is the low profile panels that use 3/8 inch tubing. Only a 5/8 inch increase in floor height. One has to plan the layout, but thinking is easier than stapling.


  • you can use pex-al-pex and get all of the "benefit" of onix there (which is really the benefit of the aluminum layer), but in a joist with extruded plates regular barrier pex and basic outdoor reset should make sure there is little to no noise.
  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,290
    Welllllllll

    How shall I say this.........

    I did one job with Onix and that was it.

    Aside from the track record of rubber tubing, I was very disappointed with the system response time, probably twice as lengthy as tube with plates. Under carpet of nearly any type, prepare to go nuclear with your water temps.

    The only plus I see for the stuff is ease of installation and handling.

    Pex with plates has to be done right to eliminate noise and it is a pain in the butt to do right.

    I try, 100% of the time to talk a customer into Climate Panel or a similar above the floor product if at all possible. The response time is the best of any radiant floor, the labor cost is about a quarter of other methods that go under the floor and water temps are far less. In my living room under hardwood the water temp never goes above 120*. Pricey to buy but I have had absolutely no issues with it. Happy customers are what keep me smilin'.
  • Mark Custis
    Mark Custis Member Posts: 539
    Mr. Ebels?

    I have not heard of climate panel. What is it?
  • MikeyB
    MikeyB Member Posts: 696
    Climate Panel

    Mark, I think S.Ebels might be talking about Viega's Climate Panel's, looks like a good product
  • Mark Custis
    Mark Custis Member Posts: 539
    Thanks Mike

    Steve may awake soon.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195


    climate panels are my choice. the install makes all the difference. I am not even considering the possible gunking of onyx. why heat below wood layers if you do not need to? Hold a heater under a typical wood floor and see what you feel come through. Granted it gets a mite colder here than in Virginia.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • Andrew Hagen_2
    Andrew Hagen_2 Member Posts: 236
    Oxygen Diffusion

    Mylar may be a decent barrier against oxygen. Obviously oxygen molecules are larger than helium molecules. I cannot find any data on the permeability of mylar film, so I cannot say.

    My main objection to EPDM tubing is that it is more insulating than pex and it leaves black gunk in the system. Also it costs more than pex, and cannot be used with extruded plates. Even if it could, why buy the more expensive tubing?
  • Steven Eayrs
    Steven Eayrs Member Posts: 33
    forget condensing.......

    if you don't use transfer plates.....which you seemed to anser for yourself. And then no use for a more $$ condensing boiler. But if you want it to be effcient and run low enough return temps, buy the plates. Really no other option I would consider below the floor. Simply doesn't work in our area in winter.
  • Bill Clinton_6
    Bill Clinton_6 Member Posts: 35


    Never could see much advantage to radiator hose. Lessee: Contrary to claims it is not easier to install. It probably is quieter than pex, but you can take easy measures in a pex installation to make it quiet. I have to believe the thick walls of radiator hose retard heat transfer and force higher temperatures. Various reports make one nervous about durability and formation of "gunk". On top of it all, it's more expensive by a wide margin. So: Why use radiator hose?

    Absolutely granted: Plates can improve output and can improve efficiency by allowing you to run your condenser boiler at lower temperatures. In my area, people turn heat on and off a couple times a day, so expansion noises are to be taken seriously with plates: I have enough concern on just this issue to scare me away from plates.

    Suspended naked pex is what I mostly use. It's output is limited to about 15 BTU per square foot, so the building insulation package has to deal with that. Fortunately, that budget can be met even in areas with below zero weather.

    The expense of plates seems to run $6.00 to $8.00 per swuare foot for materials. Extra labor expense runs $3.00 to $5.00. Overall premium for plates for a 2,000 sq ft house, then, can be as much as $26,000.00.

    Ya pays your money and you takes your choice.

    Bill Clinton
  • Mark Custis
    Mark Custis Member Posts: 539
    Bill

    Then you pray it works.
  • EricAune
    EricAune Member Posts: 432
    PEX is better, cheaper & easier.

    I have found no real benefit using heat transfer plates for a staple-up application. They will definitely increase the amount of expansion noise throughout the system, also the cost. They are very expensive too. Sizing the system with the proper Btu/sq ft will allow for the proper amount of PEX and compensate for the transfer "loss" by not using the plates.

    Using PEX allows for me to carry one set of tools and fittings for installation. Rad hose "gunks up" and is actually more of a pain to work with.

    Eric

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  • Bill Clinton_6
    Bill Clinton_6 Member Posts: 35
    Mark:

    Always has worked for me: 12 years doing it, dozens of installations, all successful. I don't know, maybe I just pray good.

    Bill


  • funny you say "why heat below wood layers if you do not need to", then use climate panel, where the put the aluminum unnecessarily under the wood layer ;)


  • then you are using weak plates.

    heavy gauge plates will drop your water temperature requirements by 30 degrees at least vs suspended tube unless your heat loads are very low (closer to 10 BTUs/sq ft than 15). That's huge. If you "found no real benefit" and used real plates, I think you missed something.


  • the san francisco bay area is a good area for suspended tube, though with the crappy insulation of a lot of those buildings you'll need plates anyway.

    as long as you're doing the math though, you should be ok: at 15 BTUs/sq ft you're still running fairly high temps on max, but with reset I imagine that penalty isn't gigantic.. and so are your yearly heat loads so a few percent efficiency probably doesn't have payback.

    again, if you're doing the math, in your area Bill I think you're probably doing the right thing. It's pretty different in climates with real winters though... even if you can get the load down, total energy usage is higher and so efficiency is more important too.
  • troy_8
    troy_8 Member Posts: 109
    Pex & Plates

    I agree! I have never installed underfloor tube without extruded plates. I need heat. (Buffalo NY) In my climate it is a joke to think you can get away without plates. Do the math! I know because I have fixed many a job that doesn't deliver the heat and or destroys the floor. I prefer to leave the garden tools outside and use pex for my tube. Never saw a reason to spend more to get less. (Rubber Hose) 3/8" pex is very flexible. Best if you use a pex with the evoh on the inside.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195


    Well the wood is less than 1/2" as opposed to 1 1/2" which many old homes have around here. granted any prodact can be put in bad if one works hard enough even Veissman can be a terrible boiler when installed wrong enough. With climate panels you better lay your loops out well too avoid too long of a run also. I still like it best.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195


    Great thing on this forum is we get folks from all over the world. Tough thing is we get people from all kinds of climates. I know 15 BTU per sq foot would be a joke even in a super insulated house. So we need the BTU's for those cold February days. This is also why we use outdoor resets.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating


  • sure, but if you made your own, it would be a better product, if you used real plates. Or used raupanel, Roth panel, Warmboard.. all products with significant aluminum, real tubing grooves, and good topside coverage.

    Or thermofin, Joist Trak or other heavy plate in the joists. in many cases (a 3/4" subfloor situation), it will perform even a bit better than climate panel. and you could go nuts with HUGE 3/8" pipe ;)

    retrofits though, if you have 1/2" I can see your point. If you have 3/4", I'd go with (heavy?) plates and plywood. a little slower to install, but a lot better.
  • Andrew Hagen_2
    Andrew Hagen_2 Member Posts: 236
    Above or Below

    I am also a proponent of underfloor heating with extruded Thermofin or Thinfin plates and pex. The fluid temps are not any higher than gypcrete floors, and an experienced installer with the proper tools can install a radiant floor much more quickly than an above floor method, which requires a bunch of wood work.

    As you say, the only time I can see installing above the subfloor is for retrofit applications. The cost is so much higher, that there has to be a strong reason to go above the subfloor.


  • well, I'm a proponent of overfloor, but not climate panel or other underpowered, high price panels.

    heavy plates in joists, heavy and light above floors do the job quite nicely. Above floor is better without much more cost.
  • Bill Clinton_6
    Bill Clinton_6 Member Posts: 35
    BTU/sq ft

    Thanks guys, for thinking about it. It's not a question of "Plates good: Suspended tubing bad." Or even "High efficiency good: Anything less bad." Even in our moderate climate, plates would do a better job: Faster warmup; higher efficiency. BUT that comes at a cost of around $8.00 to $10.00 or even more over and above the cost of suspended tube. If you are really, really serious about carbon footprint, global warming, and so on you might do it anyway. Most people couldn't justify the cost. So should they go to scorched air instead? Doesn't make sense to me.

    By the way: It's not the climate, it's the heat load that determines whether 15 BTU/sq ft is enough. There are building methods that meet that budget in even sub zero climates.

    Bill
  • 15 but/sq ft is pretty easy to attain here in Northern ILL

    My 2800 sq ft 1906 wood frame two story is at about 16 btu/sq.ft. at a design temp of -4F with 700 sq ft of glass. I also use alot of suspended tube with some plates at high heat areas...two story entries and under windows. If budgets would allow, more plates would be great, but HVAC always gets squeezed in new homes.

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  • Andrew Hagen_2
    Andrew Hagen_2 Member Posts: 236
    Methods

    How do you do above floor? In my experience, above floor is generally cost prohibitive because of the additional labor and woodwork involved. Thinfin-C below floor is generally the best balance of cost and performance in our 9400 HDD climate here in Butte.


  • plywood isn't expensive, and neither are tablesaws. A little thermofin "U" or lightweight plate and boom.. not much slower than climate panel, really.

    above or below floor is kind of a dice roll for labor, really.
  • Andrew Hagen_2
    Andrew Hagen_2 Member Posts: 236
    Labor

    I guess for a DIY it wouldn't be much difference, but most people would rather not pay their heating guy to rip plywood sheets, and return bends can be a pita unless factory-cut bends are used. The wood flooring guys generally dislike working with tubing above floor too.

    I can see where in certain circumstances, above floor could be nearly the same cost as below floor. Above floor installations definitely make for an extremely solid floor too, and the operating temps are very close either way.

    I like to keep the heating out of the way of as many of the other trades as possible, and installing below the subfloor accomplishes that.


  • most projects have a builder on them with saw-skills... works out pretty well. builder get it "pex ready" and heating guy does plates/tubing. not too bad. or DIY of course. but even if it's just heating guy, you still have to cut quik trak.. so vs other overfloor panels, it's not that much more work if you have much carpentry in your blood.

    Above floor can beat underfloor temps significantly, it seems. heavy plates in both cases, you'll drop a good 10 to 15 degrees over underfloor if the wings are on top of the plywood. it's high output stuff.

    but underfloor certainly is safer... that's important on some projects too, agreed.
  • troy_8
    troy_8 Member Posts: 109
    Bill

    You are correct- It is the load that counts. And if the loads are truly that low than great don't spend the money. But- most design to +10 deg. in my area. We had over a week below 0deg. Mostly below -10deg. That is a 20deg. swing below design for days. 50deg. inside temps for my customers = I messed up. I'm not advocating oversizing too much but I think you need a little room to increase output in severe weather. Just the addition of plates makes a big difference in output. I find the plates adds about $2.5/sq.ft. Not $10. I know it is real money but almost heating the space or heating it most of the time is not good design in my book. If my truck started in most weather I would get it fixed not accepting that it is just too cold for a week a year.
  • Bill Clinton_6
    Bill Clinton_6 Member Posts: 35
    Hi, Troy

    I can buy 4" wide x 48" long extruded plates at $6.25 each for a total of $4.70 per square foot increase material cost for area covered. If you cover just 50 % of the floor, that's $2.75 per square foot. For a 2,000 square foot house, that's $5,500.00. That's just for materials.

    How about labor? You should be charging at least $1,000.00 a day for your time (I know, that's often hard to get) and you have 752 of these things to screw to the floor and pound the tube into. I would allow a week to do this, maybe more, so the labor portion is around $5,000.00, for a total of $10,500.00.

    Now, if that's what it takes to heat the house properly, then, by gosh, that's what you should do. But, if you can do the job with bare tube that's a lot of money to save.

    Bill


  • well, hold on bill. You're acting like suspended tube doesn't have any hangers to mount... screwing up hangers vs stapling plates, I am not sure I would say suspended tube is that much faster. I do hope you're not using staples for naked pipe installs... I've seen some pipe chew itself to death after several years in such installs...
  • troy_8
    troy_8 Member Posts: 109
    Bill

    I was speaking of the additional cost. I am assuming you are using some form of suspension brackets or clips which cost ? and require ? to install. As I stated I haven't installed tube without plates- so I can't say what method works best. I can tell you that the plates hold the tube tight. We use a palm nailer with a rubber head to insert the tube. It goes in pretty fast. It does require a compressor and hose. We just completed a 3000sq. ft. house(new) in 4 days. 2men. We use a Hitachi 16ga staple gun to put up the plates. That time was for drilling holes mounting plates and weaving and installing 3/8" tube. Now- it's on to the manifolds and piping.
  • jb_13
    jb_13 Member Posts: 10
    Thanks! Pex and Plates

    Thanks to all for a very knowledgable discussion.

    I'm really leaning towards pushing my sub to pex and plates.

    More Questions:

    (i'm in Northern Va - moderate heating climate, planning staple up under open joist bays due matching existing and addition floor elev. and will heat through 1-1/4 to 1-1/2" of wood to warm through. there will be space rugs but no full carpeting). will have heat pump air system for backup/less freezing days.


    1. If 3/8 pex is easier to work with than 1/2" pex - what are the flow rate and temperature increases and extra strain on pump/decline in mod con boiler efficiency(TT)? Could we go with 3 runs of 3/8" pex per joist bay to compensate - depending on btu/hr load of room needed? worth it or just go 1/2"? What's the general btu's/hr per linear foot difference in 3/8 and 1/2" for a given temp. Or what temp or flow rate elevation are required for 3/8 to match 1/2" output?


    2. The best make/type of pex to go with?


    3. Can I go with heavy plates in critical areas and use some sitebuilt/thin aluminum plates in other areas for some increased transfer but save me $thousands on super pricey plates.
  • troy_8
    troy_8 Member Posts: 109
    Plates and tube foamed

    3/8" and 1/2" tube give very similar heat output. The difference is the max loop length. We max out at 250' for 1/2" and 200' for 3/8" We install plates and tube first leaving 3' tails along a central line. Then we run our extended manifold and connect the tails as we reach them. We use Dahl valves with balancers on one side. This allows later loop balancing. You can reverse return your piping to equal the distance between your heat source and each individual loop. Don't bring all your tube back to a central point. You will waste usable loop length and the job looks sloppy. Beware of cheap plates! Light weight plates don't do much but make noise. I would bet you will end up ripping them out. You can run plates at exposed areas and not cover the entire floor if the floor will be accessible at a later date should you require additional plates.


  • loop lengths always vary based on flow rate requirements, which depend on load and desired temperature drop (read: average temperature) across the loops.

    I just did a 3/8" job with loops ranging from 200 feet to almost 400 feet in length, central manifolds to remote areas, regular up15-58 system pump on a 5k sq ft house. 0.2 GPM can go quite a long ways in 3/8" pipe with 10 feet of head available.

    there are no rules beyond flow, friction, and available pump head. 3/8" might increase the number of loops you need in higher flow requirement situations (high load, big area, carpet), but that's it, really. it's great stuff. If only all the panel manufacturers had a 3/8" option, it would be all we used.
  • Andrew Hagen_2
    Andrew Hagen_2 Member Posts: 236
    woodwork

    I guess to me that is pushing part of the cost of the radiant floor from one trade to the next to make the above floor method appear less expensive than it really is. How does one lay out the tubing if the carpenter is doing the sleepers? I have always installed the Thermofin as the sleepers were installed to assure a tight fit and proper layout. I'm sure the carpenter would rather not be responsible for the tube layout.

    I like to be responsible for the entire job, so that if something is not installed correctly, there is no one to blame but myself. The details are very important with these dry systems. One can buy pre-cut sleepers, in fact I had a role in developing such a system, but there is significant cost associated with that woodwork. My personal conclusion is that underfloor extruded plates are the most cost effective low temperature option when that option is available. The operating temps really are only a few degrees higher, certainly nothing that would significantly affect the efficiency of the boiler.


  • wood workers cut up wood cheaper than heating guys. but the dynamics are different on every job, with every builder, and every heating guy too.

    it's not hard to get a woodworker to do a basic serpentine though and zip a few crosscuts in later if needed.

    and I disagree with the water temp calculation. adding a 3/4" layer of wood and eliminating downward lateral conduction has got to have more than just a few degrees of effect. If you do any calcs with any installation method, adding almost a full R to any method is going to do more than add a "few" degrees.. you're talking at least 10.

    Crippling? not necessarily.. but significant. Much more so in some cases than others. For instance, if you use heavy plates overfloor just in the room that needs them, then lightweights and PAP elsewhere, you chop significant material cost out of the equation. anyway; it's not to say under is the wrong thing to do, it's not. but it's not the only answer either, that's all.
  • Andrew Hagen_2
    Andrew Hagen_2 Member Posts: 236
    Efficiency

    Even at the typical operating temperatures for under floor fin, the efficiency of the boiler is between 95% and 98% depending on the burner modulation, so there really isn't a lot more to be gained by further reducing the temperature The efficiency curve has pretty much leveled off by the time the system reaches 110°F.

    I guess 10°F is a compromise I am willing to make, because in my case the installation is much less expensive for under floor extruded plates.

    Every case is different, so I can't make blanket statements. That is just my take on the issue based on the economics and issues I face.


  • I haven't seen that on a boiler curve efficiency chart, though if your heavy plates under the floor are running at 110 in a given situation, then there probably isn't a whole lot to gain going overfloor except better solar or heat pump utilization.



This discussion has been closed.