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Radiant Heat Tubing Location

Brad White_9
Brad White_9 Member Posts: 2,440
Radiant ceilings are fine where you have no other choice, don't get me wrong. Radiant is exactly that, radiation and the intensity decreases with the square of the distance. You walk on the floor (unless you are a fly or Spiderman). The tendency is to bathe yourself in a warm (but not too warm) radiant flux.

Your body is a radiator too, your head and neck being more so. (Blood flow does not restrict to the brain; your body will sacrifice the extremities to preserve the brain when the chips are down in an extreme example.)

Hence if all of the heat is emitting from the top down, you may feel too warm. Your head cannot emit the heat IT wants to. Your feet however are another matter. Unless you are a penguin (maybe you are, we have not met) your feet would tend to feel colder well before any part of your body. Hence they appreciate the warmth.

Think too if you are in a large, cavernous room, heated only from the ceiling. The intensity of that ceiling would drive anyone in a loft space down. But if heated from the floor, the upper level temperatures matters not. Comfort is where you walk.

A tad abstract perhaps, but that is how I see and feel things.

Good for you for questioning what you hear. That applies here as well. We should all do more of that, even within ourselves.

Best Regards,



  • Ron Root_2
    Ron Root_2 Member Posts: 12
    Radiant Tubing Location

    Had a conversation with a co-worker on radiant heat. I always thought tubing in-floor was the norm. He's telling me tubing in the ceiling is better! I've seen it in both and in walls but never gave it much thought as I've never been involved in the design and installation of a radiant system. Got Dan's book "Hydronic Radiant Heating" and can't find any reference to this as far as which is better. I would think in-floor would be more cost efficient (labor). Heat moves to cold, and I don't understand the benefit of it being in the ceiling, high or normal ones. I don't know this guy well enough to know if he's talking just to hear himself. I listen to anyone, and then go look it up to understand what, and if they know what they're talking about. It's not in the book, so here I am asking for clarification from the experts! Thanks guys, or ladies.

  • The answer, as in most things, is "it depends".

    Ceiling is cheap and easy to install, and operates at low water temperatures. Thus it is efficient and it is quite powerful, more powerful than floor in many cases. It certainly makes a truly excellent source of backup or supplemental heat in nearly all cases. According to my material cost analysis, it's second only to slab installs in already planned concrete in radiant costs. Often even cheaper than those crappy suspended tube systems working at 160 degrees. Not bad.

    However, it's true that it is not a heated a floor and comfort can vary. the heat curve floor to ceiling isn't necessarily all that different than radfloor over the height of a human, depending on your loads and ceiling heights, except at the floor where obviously a heated floor will be warmer. if you watch your ceiling surface temperatures in relation to your head height so you don't get a 'hot head', you'll be quite comfortable. That's not hard to do. Lower ceiling heights make this more critical to watch.

    Generally, I look at ceiling as a very desireable option when:

    1. Floor is too expensive to do right. Then ceiling gives you a ticket to low temp, efficient, and very comfortable heat at a lower price tag.

    2. An upgrade from baseboard or other areas that would not have radiant otherwise. avoid the cost of multiple temperatures, upgrade the comfort in those areas... many times this can nearly be a wash in price for a true comfort upgrade.

    3. In low load buildings where radiant floors won't really be warm most of the time anyway. In those cases, heating the floor is a waste of money. Save the bucks, hit the ceiling, call it a day.

    It's best over carpet, and if the floor is not over cold space it can absorb the radiant energy nicely that way.

    Major other advantages do include:

    -No one will put a rug on it later.
    -You don't need to worry about even surface temps, so wider on centers can be used
    -your max output is higher (again, depending on ceiling heights) at very reasonable water temps.

  • Tim Doran
    Tim Doran Member Posts: 208
    ASHRAE Standard-55

    The thermal comfort standard says that ceiling surface temps should not exceed 100f in most cases. So if the surface is 100 and the ambient is 68 and the transfer coefficient is 1.2btu/sqft/f then the output is 38.4 btu/sqft. Overall it is about the same output as a floor. One other consideration with ceiling systems is that objects in the space can cast a shadow, so to speak.

    Tim D.
  • hr
    hr Member Posts: 6,106
    Tim, why

    the coefficient of 1.2? I've always heard 1.7, 1.9, or 2.0 for floors??

    I will say having lived two seasons now with low temperature radiant ceilings, they do have some nice advantages. Response time and that warm sun feeling when you walk into a room.

    All things being equal, however, I would still give radiant floors the slight advantage over ceilings from a pure comfort perspective.

    My feet seem to run colder as I age. NOTHING feels nicer after a long day working outdoors in the cold then warm floors.

    Much easier to lay cloths and footware on floors than ceilings :) Nothing nicer than warm clothes to jump into on a cold morning. Especially if you sleep in a cold bedroom :)

    And warm tile bathroom floors wnen you are wet and naked... need I say more :)

    hot rod

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  • Gordy
    Gordy Member Posts: 9,546

    I can say as a homeowner with radiant ceilings, and floors.
    The radiant ceilings are quite nice. My supply temps run in the 115* range. I have 8' ceilings through out, and I do not have the hot head feeling, also the floor temps where I have the radiant ceilings are with in a couple of degrees of the room set point. My radiant floors are in the basement. I have a sun room which has radiant ceiling , and floor. Would not give up either one. Hot Rod is right when you lay on the couch its like the gentle warmth of the sun.

    I will say with the radiant ceilings you are not limited to floor covering choices. Also you do not have furniture restricting output with radiant ceilings. There is some shadowing when sitting at a desk or table but that is getting anal about it.

    Rob makes some good points on the installation side also. All in all they both kick butt. Getting people around the heat rises theory, so radiant ceilings are inefficient can be trying some times though.

    My system has been operational since 52 seen a couple of winters in the - 20 to -30 range so it has the output considering -9 is design temp in my area. The original attic insulation was 5" of vermiculite....ahhh when oil, and gas were cheap!

    Hot Rod do you still have the designer ceiling radiant or did you drywall over that. Remember some pics a while back of pex in plates screwed to the plaster ceiling looked kinda groovy.

  • Weezbo
    Weezbo Member Posts: 6,232
    There are many places that the main source of Heat is radiant

    there are homes that are designed about radiant everything and direction concievable*~/:)

    "if it's Radiant,...It's In There" :)

    I have a radiant Rock in my home :)

    last winter i installed a radiant Beam :)

    my thought is,.. Better than What? the next thought is

    40% bran flakes.... Put the radiant in there, someone will like it :)
  • Tony_23
    Tony_23 Member Posts: 1,033
    My Old House

    I put radiant floor in our "new" 130 yr old farmhouse. It's actually comfortable at 62-64 deg F air temp. However, when I sit in my La-Z-Boy, it "shadows" me from the heat. In this instance I would also like a bit of ceiling radiant. My plan for the second floor IS ceiling radiant.

    Kind of interesting living in the "laboratory" :)

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  • Tim Doran
    Tim Doran Member Posts: 208

    It seems that the transfer coefficients have been overstated for walls and ceilings in the past and research done in Denmark and Germany has concluded that the normalized coefficients are, ceilings = 1.2, walls = 1.6, and floors = 2.0. The radiant transfer is always at or near 1 btu/sqft/f and the viriation comes in on the convective component. These figures are the basis of the current European design standard which was enacted in Brussels three years ago. There is still some controversey around this but these are widely accepted as the figures to be used.

    Some feel that the old coefficients are based on reduced surface area and higher temperatures at the surface. In other words, we used to do the perimeter of a ceiling and run it hot which still allowed for good convection as the air would cool in the center of the room and then drop to be pulled back towards the edges. The limitation of 100f is the kicker and would require the use of more area and therefore reduce the potential convection.

    In cases where the AUST(average uncontrolled surface temperature) is significantly cooler than the space set point the transfer may be greater as any radiant panel is driven by what it sees. Distance and angle or view factors come into play here and it gets complicated quickly. Hope this helps.

    Tim D.
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