Retrofit underfloor radiant heating?

Discussion in 'Electrical Forum discussion & Blog' started by LarryG, Dec 12, 2009.

  1. LarryG

    LarryG New Member

    Dec 12, 2009
    I am in the middle of 2 bathroom remodels. One has already had the wet-bed and tile installed on the floor. Is there a way to safely and efficiently install underfloor radiant heating? The rooms are on the second floor and the ceiling below have been removed to expose the underside of the subfloor. The subfloor is 1x4 tongue and groove. There is about 1 1/2" to 2" of wet-bed and pebble tile. My concerns; will heat radiate up through the wood subfloor, and will the heat damage the floor joists or subfloor? If this can work any suggestions for manufacturers or brands?

    I do not have hot water heat in the house and would hope to use an "electric tape" type heat source.
    Last edited: Dec 12, 2009
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Hindsite is expensive! Do you have a boiler? You have a lot of mass to heat up. Electric would have worked in the floor sandwich (i.e., under the tile), but I don't think anyone would recommend it as a staple up. Hydronic staple up would work, but your supply temperature will need to be much higher (and thus less efficient) plus, you'd need plate diffusers to spread the heat more evenly. Response rates will be very slow. Either would have been much more efficient and easier to install as part of the mud bed underneath the tile.
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    Wood is a very poor heat transfer medium, so you need a lot of temperature to penetrate it, then you also have to heat the subfloor and tile. Most electric panels have a very small BTU factor so they would probably have to work almost 24/7 to keep the floor warm.
  5. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Jun 16, 2007
    Licensed Electrical Contractor
    NY State, USA
    I have NEVER seen an electric system to work this way, only water.
  6. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Jan 5, 2009
    Used to be in IT
    South of Boston, MA
    They do make them, I looked into them for our kitchen
    Basically they come in rolls that fit between the joists
    You'd need to most likely push rigid insulation up under them to trap the heat & heat the floors & not the air
    I never looked into it too much, decided against it as the kitchen has a large radiator

  7. jar546

    jar546 In the Trades

    Feb 20, 2008
    Don't waste your money, time or effort on an electric system in this particular case. You need a hydronic system.
  8. mulveykemster

    mulveykemster New Member

    Dec 31, 2009

    The newly constructed houses are now coming with the new Underfloor heating system. Underfloor heating systems require a wooden or tiled flooring to be effective and to work efficiently. The feel of suntouch com with underfloor heating makes you feel better. Hope you need this..
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