Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.

Floor Output

I have a customer that routed 3/8" PEX in a plywood floor.  He is covering it with 1/2" plywood and then 5/16" cork.  Can anyone tell me the BTU output per square foot of such a floor?



Thanks.
Often wrong, never in doubt.

Comments

  • Charlie from wmass
    Charlie from wmass Member Posts: 4,200
    more questions first

    water temp, loop lengths, pump used for an idea of the gpm. any heat transfer used like caulking and/or aluminum plates?
    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
  • No Plates

    Yes, unfortunately - so far - no plates, so output will be limited.  Water temperature - 130 degrees and no caulking.
    Often wrong, never in doubt.
  • CMadatMe
    CMadatMe Member Posts: 3,085
    R-Value

    The ply is easy that has an R-value of .63. The 5/16 cork is what? Tile or flooring.



    Try this......   http://www.wecork.com/products/floor-tiles/installation/
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • Let's try again

    The plywood is actually 5/16" and the cork is 1/8".



    I'm helping a friend out with his garage/work studio addition, but he got a little too ahead of himself and routed the bare tubing into the floor.  I'm afraid his output will be less than 10 BTU's/sq. ft. and he needs 40 BTU's/sq.ft.



    I suggested Raupanel and Thermalboard, but he thinks it will be too much work or it's going to mess up his floor elevations.  I've suggested a large Runtal radiator.  The heat source is his domestic water heater via a Taco X-Pump Block.  Any other ideas?



    Alan
    Often wrong, never in doubt.
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    edited June 2011
    that will be better

    than naked staple up pipe. I think you'll be around 15 BTUs/sq ft as long as you're around 8" o.c. with 130 degree SWT and a reasonable drop.



    you were never going to get 40 BTUs/sq ft out of a radiant floor anyway though, unless you were doing concrete and tile or something.



    I'd recommend radiant ceiling and a 120 SWT max. If you really need 40 BTUs/sq ft you'd want 8" o.c. or so.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • Excellent idea, Rob!

    It would have to go in the wall since it's an exposed beam ceiling.  What product do you prefer?  Raupanel? Thermalboard? QuikTrak?
    Often wrong, never in doubt.
  • CMadatMe
    CMadatMe Member Posts: 3,085
    Have You Thought

    About adding a panel rad sized for the same temp for make up or even radiant panel baseboard as an additional loop? Take the kick molding off the wall and replace it with panel board. Same look better feel.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • hot_rod
    hot_rod Member Posts: 15,363
    also check out

    some of the low temperature radiators from Jaga..They give amazing output with 90- 100F supply.  Some really wild styles too.



    Smith of MA has a large fin, low temperature baseboard.



    For a retrofit wall check out the Roth panels.  Foam with aluminum surface.  use foam adhesive to install them then a covering of sheetrock ot thin, engineered wood products.



    The floor output is related to how warm you can get the surface temperature without damaging any of the coverings.  The rule of thumb is about 2 btu/square foot for every degree difference.  80F surface- 68 ambient = 12X2 about 24 btu/ square foot.



    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    usually

    we just use light plates and PAP tubing with 1x3 strapping. if I was going to do a prefab I'd probably opt for warmboard.. would be more stable for drywall... but Roth would be good too from a thermal standpoint, I just don't know about drywall over roth... maybe you would need sleepers?



    Wall is great for a couple of reasons though, first you still are only fighting drywall for heat transfer, and second people will tolerate huge temperature asymmetries in walls. so if you had a tile section of wall, for example, you could really crank out the output with higher water temps (drywall wants a 120 max I've been told). but I get concerned about puncture risk and typically prefer radiators for the visible obviousness/lack of puncture issues.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • Gypsum and 120 degrees

    So, using a product like Raupanel on the wall, why does the gypsum limit water temperature to 120 degrees?  Does it break down? 
    Often wrong, never in doubt.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    Gyps not the issue....

    Paint and wall paper glue are the weak components in the mix. I think that Siggy first recommended those limits when he did his wall. I've run 160 degree F water through my gyp/paint radiant ceiling in an effort to accelerate a cold cabin, and I forgot to turn it down, and haven't suffered any paint peeling off the ceiling. Of course, I am running on an outdoor reset as well, so it only sees real hot water 2% of the time.



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Thanks, Mark.

    I wonder how water temperature relates to surface temperature, i.e at what wall temperature does the paint start to peel?
    Often wrong, never in doubt.
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    we question it

    it is supposed to hurt gyp to get too hot, but we had a client doing VSI on a cast iron boiler that had serious heat migration/ghost flow through the injection circuit, turning his radiant ceiling into an on/off high temp emitter. and no issues noticed over a couple years of operation. but I abide by the 120 because it does give a max output that is in like with the max limit for thermal comfort, I believe.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • hot_rod
    hot_rod Member Posts: 15,363
    possible expansion issues

    when a sheet of sheetrock goes from room temperature to 120F or more?



    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    No sheetrock issues on my watch...

    In fact, my unheated ceiling has more cracks than my heat ceiling does.



    I do agree that having real hot water going through the panel does make for hot head syndrome tho...



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
This discussion has been closed.