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Radiant Ceiling spacing effects

Robert_H
Robert_H Member Posts: 135
Our heating retro plan uses cast iron radiators throughout the first floor except in an attached office. The office is 99sqft (inside dimensions) with several layers of old floor over a well insulated crawl space. The perimeter is almost covered with two desks and many filing cabinets leaving little exposure for radiant floor, baseboard or a radiator. So I am looking at radiant ceiling for this room. In the rest of the house the radiators are oversized which should allow lower water temperatures and I don’t want to end up with this room over cycling the boiler if I can avoid it. I’ve done a few layouts in visio and with an 8” spacing I can run about 136’ of tube and with 6” spacing 173’ of tube.

In general does this kind of difference in tube quantity and spacing reduce the water temp requirements enough to make it worth wile? I’m not really concerned about the cost difference of the additional tube and aluminum plates.

If it matters the heat lose in the room is 5564 btuh.

Comments

  • STEVEusaPA
    STEVEusaPA Member Posts: 5,320
    Quick question...

    Are you sure about that heat loss number?  Seems high for 99 sq ft.  Are the walls, and ceiling not insulated?  Did you calculate insulating the ceiling before you put the tubing in?  Does this office have 3 exterior walls and/or lots of large windows?

    If all of that is correct, then 56 btu/sq feet will require a pretty high water temp, if it's even do-able. 
    steve
  • hot_rod
    hot_rod Member Posts: 15,055
    So a heat load of

    5564 btu/ hr with 100 square feet of heat emitter? Then you would need 55.6 btu/ sq. ft. A bit high for a ceiling output. Check your load numbers again.



    A rule of thumb about .7 btu/ hr. / sq. ft. for every degree difference between room temperature and average supply temperature in the tube and plates.



    So 130° supply - 70 room temperature X .7 = 42 btu/ sq. ft.



    I've heard 130- 140° max for supply to sheetrock ceilings. 140° supply, 20°∆T would be an average of 130° supply.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Gordy
    Gordy Member Posts: 9,514
    1/2 your calcs

    I would say even 25 buts a sf may be high.



    A side note IF your heat loss is that high, and you spend lots of time at a desk you may notice some shadowing effect. This is where the desk is blocking radiant output to your legs and can be noticeable when ceiling output is high. Not a huge deal, but does happen with higher water temps.



    And yes tighter spacing lowers water temps, but there is a point of dinishing returns.
  • Rich_49
    Rich_49 Member Posts: 2,617
    Small rooms

    with windows have high loads , too much infiltration . Remember guys the best window is still a SH*&^y wall . This room can't be done from the ceiling .  I would advise using a floor convector from Smiths Environmental or similar .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Robert_H
    Robert_H Member Posts: 135
    Heat loss update

    First off, I really appreciate your replies.

    I’ve tried several programs to run the heat loss Uponor’s, Taco’s FloPro and a spreadsheet created by Andrew Ensminger(Crown).

    After your prompting I realized I had not updated the heat loss calcs for the insulation I added and will add to the overhead.

    Current heat loss calc is 4110 by Uponor and 4770 by the spreadsheet.  Uponor does something weird (to me) and the heat loss changes as you add a heat source.  



    In case anyone is interested here are the the room construction details:

    Built early 1900s mill town (budget) construction

    99 sqft, three exposed walls, unheated crawlspace.



    One wood panel entry door with storm, not used and sealed up pretty well.

    Two 2.5*5 Anderson double pane wood windows



    8’ ceiling that was originally a vaulted ceiling and a previous owner added the sub ceiling with no insulation and not enough nails in the drywall so it was falling in when I bought the house. The gap between the vaulted ceiling and the roof sheathing is also un-insulated. I have insulated under the vaulted ceiling and the exposed gable end with 2” pink board (R10) and sealed all with expanding foam then drywall over that to seal and as fire barrier.

    I have removed the drywall from the sub ceiling and brought the framing to 16” OC (2x4). I plan to insulate with R11 batts or blow in cellulose after I get the heating system installed.  I’m calling the above space insulation R22 in my calculations.



    Walls: three exposed, originally with 4” of blown in insulation. However, I had to remove the bead-board on one wall and the insulation had settled a foot or more so I squared the gaps and filled them with R11 and dry walled over.  The other two exposed walls probably have the same settling problem. Knowing I will fix it in a few years I just call the wall insulation R11.



    Under space insulation is R19 fiberglass and the crawlspace is not insulated but it is has vapor barrier all around and very well sealed against infiltration



    Thanks

    Robert
  • hot_rod
    hot_rod Member Posts: 15,055
    Consider the Roth Panels

    it is a foam board with grooves for the tubing and an aluminum layer. it is light and easy to install. get some foam adhesive in a caulk tube, make sure it is foam adhesive Liquid Nail and others will dissolve into the foam.



    Then get some grabber screws with large washers. I use the plastic washers from those roofing cap nails, to screw the panels to the ceiling until the adhesive sets.



    This would allow you to use the 6" spacing and give you wall to wall aluminum conductor.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Robert_H
    Robert_H Member Posts: 135
    re: Roth Panels

    Thanks Hot Rod, I'm looking into that. what document did you get those second two images out of?
  • Robert_H
    Robert_H Member Posts: 135
    cool feet

    Thanks gordy, I was thinking about the shadowing effect also. It seems that radiant ceiling would be great in bedrooms or living rooms but not places where you spend a lot of time with your feet under a table or desk.  I'm considering heating both the ceiling and the exposed part of the floor as an option.
  • hot_rod
    hot_rod Member Posts: 15,055
    Idronics 6

    is the source of that picture. It is a technical journal on Solar Combi Systems and how to use low temperature emitters with solar thermal.



    http://www.caleffi.us/en_US/caleffi/Details/Magazines/pdf/idronics_6_us.pdf



    A whole series of these helpful journals are available for free at www.caleffi.us
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • SWEI
    SWEI Member Posts: 7,356
    Insulation upgrades

    should be on your radar.  Find an applicator who does wet-spray (damp-spray) cellulose and have them replace the R-19 under the floor with that.  You can also blow way more than R-11 up above.  Even under a low-slope attic, you can usually get R-40 or better.
  • Gordy
    Gordy Member Posts: 9,514
    ceiling output

    My master bedroom is 252 sf. over crawl space r-19, Three exterior walls, lots of glass. 50's construction. 10857 btus heatloss.



    Nothing but radiant ceiling 115* supply temps. And it works beautiful. But my ceiling radiant is copper tubing 6" OC embedded in plaster. Is it better than Roth dunno.



    Its doable Rich easily.
  • Rich_49
    Rich_49 Member Posts: 2,617
    Robert

      Ran your numbers on Uponor ADS 7.2 as stated above . 

    Loops    2

    Loop length  152' @ 6" centers

    AWT     103*

    Surface temp    82.1*

    Design Temp Drop  20*

    BTUh sq ft    22.6

    Total heat load  3387 BTU/hr
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Robert_H
    Robert_H Member Posts: 135
    ADS file

    Interesting Rich, can you email me the ADS file so I can compare how you got your results vs how I got mine?

    [email protected]

    or attach it here which ever is most convinient

    Thanks

    Robert
  • Robert_H
    Robert_H Member Posts: 135
    Thanks

    thats a lot of good dope!
  • Robert_H
    Robert_H Member Posts: 135
    Rich

    Why two loops in that calc? I would think in a small circuit like this one loop would be fine. But there are many things I don't know yet!

    Thanks

    Robert
  • Gordy
    Gordy Member Posts: 9,514
    Loop lengths

    If you did one loop it's length would be 300 plus feet. Doable but larger circulator would be needed do to higher head which in turn would increase operating costs.



    Also more even temps with shorter loop lengths.
  • Rich_49
    Rich_49 Member Posts: 2,617
    Robert

    I sent those files to you but you have not opened them . Why?    Gordy's explanation is dead on .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Robert_H
    Robert_H Member Posts: 135
    makes sense!

    Thanks Gordy
  • Robert_H
    Robert_H Member Posts: 135
    Because I have not recieved them

    First off, thanks for taking the time to help me with this!



    When did you send them and how?

    I have checked my email and I haven't received anything, yet

    I checked my inbox and spam folder.



    Did you send them directly to [email protected]  directly or through the "contact this user" feature here at heating Help? Ive been having some problems with that. 
  • Robert_H
    Robert_H Member Posts: 135
    Got them!

    Rich, I received two files from you this morning and will look at them later today. Thanks!

    Robert
This discussion has been closed.