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Commercial Tubing Install (BRRRR!!!)



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  • Paul Rohrs_4
    Paul Rohrs_4 Member Posts: 466
    27F outside and 45 MPH winds = 8F windchill

    We did have a roof over our heads, but it made for a really long day.
    Matt J and I finished 10ea 600ft loops in the parts warehouse. I won't tell you Matt's age, but he is 6 years older than me, and I suspect pound for pound, is one of the toughest people I have ever met. I was a hurtin unit by days end.

    Anyway, this warehouse was the final portion of our tubing install in the new Caterpillar facility. The parts warehouse had 10ea 600 foot loops that were supposed to be 15" OC with 6" banding on the South and West sides as drawn in the "Nebraska Machinery Parts Warehouse" picture.

    About the 9th loop, we did need to tighten up our spacing to 6" OC to make all 10 loops fit in their entirety.



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  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124

    I did not see insulation....did I just miss it or is there a differsent strategy here? Nice work. My back and knees hurt just from looking at it...kpc

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  • Paul Rohrs
    Paul Rohrs Member Posts: 357
    No Insulation below slab

    I should post the heat-loss that came with the job.




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  • Do I recognize that tubing?

    Is that 3/4" Onix you're using on this one?

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  • Kevin O. Pulver
    Kevin O. Pulver Member Posts: 380
    I feel your pain pal,

    did you ever get those fancy zip tools working again?
    I'd like to see one. Kevin
  • Paul Rohrs
    Paul Rohrs Member Posts: 357
    Survey Says!...

    That was 5/8 onix and it was some of the easiest tube we have ever put down.

    Matt J (the Iron Man) performed a "clip-tie tool-ectomy" and got them both reconditioned and back up and running.

    Good to hear from you Kevin, you must be busy as well.




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  • ScottMP
    ScottMP Member Posts: 5,884
    Little different

    than sitting at the desk, Paul ?

    That looks like ALOT of work. I thought you were using Insultarp , but you say No insualtion huh ?

    Nice work


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  • Andy_14
    Andy_14 Member Posts: 121

    Nice looking install. BUT what gives? Why no insulation? I've rarely ever heard the "experts" recommend not using insulation under the slab and most importantly around the perimiter.
  • heatboy
    heatboy Member Posts: 1,468
    I feel your numbness........ :-)

    We did this one in January of 2004. I have never been colder in my life than those two days. 15° with a howling wind. 5/8" Wirsbo hePEX. You can imagine how flexible it was!

    The Radiant Whisperer

    "The laws of physics will outweigh the laws of ecomomics every time."
  • Paul Rohrs_4
    Paul Rohrs_4 Member Posts: 466
    I emailed Watts Radiant with my questions...

    and with his permission, I will post his response my questions concerning heatloss, Delta T, and response time.

    Keith Whitworth responded and I must say his answers are brilliant and dispelled any other questions I had about commercial applications. I have not seen Keith post here before, but he would be (and is) a huge asset to the industry. Here is his response...

    * * * * * * * * * * * * * * * * * * * * * * * * * * *

    "Some things that drive heat load are: high ceilings &walls, lack of insulation, many overhead doors, etc....

    It is not uncommon to see loads greater than 35 Btu/h-sq.ft in commercial applications. The amount of energy we can derive from the floor is chiefly dependant upon the temperature difference between the uppermost floor and the rest of the structure (the Average Unheated Surface Temperature-or AUST-of the objects in the space). RPA's guideline would hold true (mostly) for an average HOUSE with a floor temperature of 85 and an AUST of 70. With a 15 degree differential we can get typically 35 Btu/hr-sq.ft.

    However, when I increase the differential, i.e. keep the floor at 85 but decrease the average AUST to 60, I can get quite a bit more energy off the floor--up to 50 or 60 Btu/hr-sq.ft. Hot goes to cold, and more hot goes to more cold at a greater delta T. Hot doesn't go to hot.... Further, the floor is always dynamic--I get more energy from the edge of a slab, where the heat load is, than from the middle of the room, where it isn't (until I bring in a huge Caterpillar diesel, which has a lot of thermal mass, then the dynamics change as required).

    So, in counter to RPA, the "cooler" the indoor design temperature, the more energy I can get off the floor. When was the last time you saw a snowmelt with a secondary heat-delivery source? And, snowmelt slabs only operate at 35-40F! Yet, we can get up to 250 Btu/h-sq.ft. from a slab (despite the unreasonable loads ASHRAE wants).

    In summary, the cooler a room and the warmer a floor, the more energy the floor "gives off"--literally, the more energy is "sucked" from the floor to the cooler objects. This is exactly what we see in commercial buildings with high-bay areas, large overhead doors, etc... Almost all radiant floor systems ("radiator floors") are self-regulating, to a degree. The warmer the AUST becomes, the less energy we can get off the floor, which in turn reduces the AUST, which in turns increases the amount of energy we get off the floor, and the cycle continues.

    The key to all this also becomes what I call the "line in the sand". When do we see a "design load"? With a forced air system--a system that does not put the energy into the thermal mass, the greatest load is on a design day, 0F, -10F, etc... But with a radiant floor system (again a radiator floor), the greatest load is *- when you first turn the system on! Trying to get thermal mass up to temperature requires greater energy than a design day ever will---on a design day the mass is already at temperature (as long as you turn the system on before then!).

    So why does everyone's heat-loss calcs ask for design temperature? Because none of us can account for thermal mass--yet. We don't know what is going to be in the space. So we all act like salmon going upstream and follow the "norm".

    So to come full circle, my point is the numbers generated by the program, Watts Radiant's Radiant Works or anyone else's, are a "snapshot" of one moment in time. They are, in reality, probably not very accurate. Until we account for thermal mass, the numbers will always be "relative", not "absolute".

    I hope this helps! If you have more questions, please ask! Thank you!"

    Keith Whitworth

    Central Regional Sales Manager

    Watts Radiant

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  • Brian (Tankless)
    Brian (Tankless) Member Posts: 340
    Excellent response from Keith

    eh? Paul.

    I bet you're breathing a sigh of relief. The enormity of that tubing layout had me seriously questioning what I believed "normal".

    We all want to know how it performs when comissioned.

    Brian, just an observer, looking in & learning.

    Edit: In NEBRASKA, I would still have insulated beneath and perimeters. They might get Tulips growing around the building, the way they did in Levitt-Town homes :O).
  • Andy_14
    Andy_14 Member Posts: 121

    Any other Pro's care to chime in with opinions or thoughts on no insulation? I'm very interested in your thoughts. Just doesn't seem correct to me, but I know very little.
  • Paul Rohrs_4
    Paul Rohrs_4 Member Posts: 466
    My mantra

    is that I never see a good reason NOT to insulate in a residential application.

    Commercially, I try to nail down expectations on response time especially if they want a setback feature. I agree on the edge insulation at a minimum, but they are definately going to have a very large earthen heat-sink below the 8" slab.



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  • Troy_3
    Troy_3 Member Posts: 479
    What did I miss?

    How does that relate to no insulation. I guess I'll reread it. That sounded like a congressman speaking. OK. Thanks for the clarification. I agree that edge insulation at a minimum is needed. We have done commercial jobs with edge insulation going down 4' into the ground.
  • jp_2
    jp_2 Member Posts: 1,935
    I'm puzzled

    how can you get 60F air temp when the floor is at 85F?
    85F seems real high, unless structure is poorly insulated.

    I must be missunderstanding something. the post seems to tell me if I need more btu's out of a floor, open a window?(the snow melt analogy)

    I can see no insulation at the center of a big structure but not at the edges?
  • Paul Rohrs
    Paul Rohrs Member Posts: 357
    Here's is what I got out of Keith's statement

    The greater the temperature difference between the heat emitter (in this case the floor) and the (AUST) walls and objects to be heated, the greater the POTENTIAL heat transfer.

    So, the colder the walls, ceiling, and items needing heat, and given the heat transfer method with enough latent BTU's to accomplish the task, the wider Delta T will accomplish satisfying the 50BTU (or greater) per sq/ft load.

    As it pertains to insulation, Keith indirectly stated that once the slab is up to temp, design conditions won't exxagerate the resulting load as long as the already widened Delta T is maintained. In my mind, as long as the 16,000 sq/ft main bay is not on a prolonged set back or trying to achieve a 60F degree room temp setting when it starts out at 40F, the system should be fine. Again, I DON'T think Keith is stating that insulation WON'T help in response time issues, but the greater heat transfer rate will not pose problems.

    This is what my take is anyway. Was I working for the Department of Redundancy Department in my statement? I hope not.




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  • Tim Doran
    Tim Doran Member Posts: 208
    AUST/Air temp

    As my friend Keith stated. The floor is driven by what it sees not by the air temp alone. The Average Uncontrolled Surface Temperature and ultimatley the Operative temperature drive the floor or radiant panel. The result of cooler surfaces ( Low AUST) is that the transfer coefficient from the radiant panel increases. So the normalized 2 btu/sqft-f for a floor may become 2.5 or 3 btu/sqft-f. This would mean that the floor would deliver more output at a lower temperature and in the case of a structure like this may deliver 40 or 50 btu/sqft with no problem. The ability of a floor to maintain a room at 60f with an 85f surface would greatly depend on the mass flow in the circuits. Surface temperature is a derivative of fluid temperature and resistance whereas output is untimaltly controlled by temperature and flow. It may be possible to have a max temperature of 85f somewhere in the floor with a relatively wide delta T that would allow this to happen. The average surface temperature would most likely be something less than 85f. Hope this helps.

    Tim D.

  • Everything he said is true, but has nothing to do with insulation.

    The slab should have edge/perimeter insulation, commercial, residential, no matter. The slab doesn't know the type of building it's in, it's one temperature, the outside is another, and it's losing heat that could otherwise be kept in the building.
  • jp_2
    jp_2 Member Posts: 1,935
    heat up time?

    so, how long do you figure it will take to heat up 16,000 sq ft of 8 inch concrete? how big are the boilers?

    can't see that "set back" would even be practical?

  • The rate of transfer is greater with a wider delta T.

    If your air temp is 60 and floor is 85, you are transferring heat faster from floor to air, in simple terms, then you are at air temp 70. Most common numbers for BTUs/sq ft outputs from radiant are geared toward residential temperatures of 65-70 degree room temp setpoints. In commercial situations or shops or what have you, it's different.

    So yeah, you could get more BTUs out of your floor if you opened a window. However you'd be doing it by increasing the delta T of the space (dropping your air temperature) by dumping excessive BTUs out of your open window. If you want more BTUs WHILE MAINTAINING THE SAME ROOM TEMPERATURE, then you have to increase delta T by increasing your floor temperature.

  • jerry scharf_3
    jerry scharf_3 Member Posts: 419
    it's not just about air tempurature


    Let's say you've got a 300'x300' high bay space and we have a 85F surface temp. The air near the floor will vary, and the heat exchange to the air will vary as well. Let's say it ranges from 60 near the walls that have downward convection flow to 70+ in the center where the air should be most still. So the furface to air heat exchange will vary greatly from the edge to the center (40+% change in delta T.)

    Then there is the radiant component. The radiant heat excahnge is determined by the average radiant temperature seen (as in line of sight) by the piece of floor compared to the surface temperature of the floor. If the room is completely empty, then they see much closer values of radiant difference from edge to center than the air temps. So if the radiant temp for all the wall and ceiling surfaces are 60F, the radiant output for the floor will be constant.

    Since we said the outside edge gets cooled off by the cooler air, then the center of the floor will take on more of the radiant heating despiste the higher air temp. This allows the whole floor to run at increased output even where there is not a wide temperature difference from floor to adjascent air.

    As for insulation, it's job is to slow the flow of heat. So to have value, there has to be somewhere where the heat is trying to go. So everything that doesn't make it out to the perimiter of the house is storage. If you look at a residential type slab that is say 50'x50', all of it is within 25' of the perimeter. If you look at the 300'x300' slab, only 30% of it is within 25' of the perimeter. If you look at the R value of 25' of earth, even at R.5 pr inch, you come up with R150, Hard to see the value of R10 insulation there. If you drop down to 15' perimeter, you need to insulate less than 20% of the commercial slab, and have someting like R90 from the edge of the insualtion to the perimemter. So investing in very careful insulation for perimter is much more valuable than putting some insulation everywhere.

    Like Kieth said, startup load is going to be huge. Heating a foot or two of earth below the slab will increase it even further. The comment about the lack of usefullness of set-back would apply in spades. On the other hand, there is a huge amount of mass to warm up a big bulldozer when it comes in.


  • That's why I said "in simple terms". I was giving the basic idea of what keith was talking about to the previous poster.

    Completely agreed center insulation is not that important for large slabs unless a high water table is present. However omitting perimeter and edge insulation in ANY slab is just bad practice and that's what it looks like happened here.
  • Constantin
    Constantin Member Posts: 3,796
    Very good points, Jerry.

    You are absolutely right, insulating where it matters most is the name of the game, and edges are usually "it". Ditto for exterior foundation walls as opposed to the slab. How many homes feature foundation walls with covered XPS on the outside?

    On the other hand, when you have the benefit of a lot of floor space and the right soil conditions (i.e. ideally dry sand), then insulating below may become optional even in cold areas of the country. The perimeter still benefits from an inch or two of XPS though while the area in the center can then be used as a thermal battery...

    As far as payback goes, I wonder how much it costs to bulldoze 12"+ of sand or pea-gravel into place that is kept dry with perimeter drains rather than relying on XPS for that job. If a bulldozer is already on hand, it may take a lot less resources to get the place insulated with dry earth than XPS...
  • jp_2
    jp_2 Member Posts: 1,935
    show me this

    """ If you want more BTUs WHILE MAINTAINING THE SAME ROOM TEMPERATURE, then you have to increase delta T by increasing your floor temperature."""

    this boggle my mind! its all connected, surface temps, radiation, btu output.....one in the same here..

    if the room temp doesn't raise where do these btu's go?

  • You're right, that wasn't very well worded. You wouldn't maintain the same room temp, you'd be increasing it. Which is presumably your goal if you are trying to get "more BTUs" out of your floor. Sorry for the confusion.
  • jp_2
    jp_2 Member Posts: 1,935
    no trouble

    its easy to get off track sometimes, besides we aren't getting paid here.

    in this situtaion i don't think you can "pick" your delt T if you want a certain air or AUST temp. its just a function of the entire structure. maybe this is where the problem lies(wording). I can see where tall ceiling height changes things.

  • I was just referring to your apparent confusion about "If you want more BTUs out of a slab, open a window". Lowering your room temperature (opening a window), while maintaining a constant slab temperature, would result in more BTUs being emitted from the slab. I guess I'm not sure where your confusion was since you apparently understand how this works? Or did I misunderstand your post?
  • jp_2
    jp_2 Member Posts: 1,935
    odd wording

    to me the post was just worded odd. I've read it several times now and see what he meant. I think a little different I guess.

    as I said before, you can't pick that delta T as he seemed to suggest, its a function of the structure. I also assumed entire floor, for the most part, would be at 85f.

    don't missunderstand, I know you can pick delt T, just not if you want a certain temp. assuming even floor temps
  • Uni R
    Uni R Member Posts: 663
    heat up time?

    I'm more curious as to what type of winter vegetables they can plant and harvest all the way around the building?
  • Matt J
    Matt J Member Posts: 2
    Just to clarify

    exterior walls are tilt-up concrete with insulation sandwiched in the center, there also is edge insulation which is not pictured and insulation 4' down on the interior perimeter. (as per code) R-10. And yes that is snow on the interior of the building!
  • Weezbo
    Weezbo Member Posts: 6,232
    not to ruin your high *~/:)

    buh year before last we had a boiler sitting in -30 lashed up on the gravel pad to two fan coils and the ice would melt under the pad each day :) it was all Hosed in with The Rehau and Weezbo putting the floor drains and radiant in that slab and the gypcrete in the house was a partiular experience I must say *~/:) took days to dial the snow out of the garage with only visquine seperating us from the hawk. a jack maddox and some stout square shovels.

    I wouldnt deny anyone the experience though . and i have to feel that you likely feel the same way too:) That was the year Rocky showed up in the morning on one of his propress jobs and someone had left the door open all night ....i was lucky , the electricians had only pulled the visquine down from the uninsulated ceiling to aid me in my endeavours :)) Good work Ladds you ever feeling real skippy we have another rough in still to do..
    :)))) and all radiant. last week it was around - 34 i bought a new thermometer goes to 100 below with 10..20...30...mile wind chill factors scaled to the side of the temps. i am feeling i ought to send you one as you are walking with God from here on out :) Ok Ok ...so is 100 below and 60 mph winds colder than 60 below and 100 mph? humidity aside for a momment...
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