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Multi-unit house Electric Radiant Floor or Forced Air/Gas?

Hi, I am a homeowner in the middle of renovating a 2 unit rowhouse to a 4 unit house. The house shares walls with a house on either side (except for new top floor which we just added). It used to be heated by forced air fueled by gas. Each unit is sq ft is 600, open living area and 2 (tiny) BR and bathrooms. The ceilings are 12ft. We will have gas stoves and a gas fireplace in each unit.

I really want to use electric floor radiant for all units but I have discovered that the per unit price of electricity in the area is 3 times as expensive as the per unit cost of gas. I want to figure out whether the fact that electric floor radiant heats the most relevant area ie near the floor where people are, means that even if it is more expensive per unit bc fewer units are used than with forced air where the air has to be pushed from the ceiling down, whether it might be cheaper in the end to use electric radiant floor heating.

Can you help me figure it out? Ie most effective and coat efficient way of heating 600sq ft with 12ft ceilings? We are hanging drywall now so I have to figure this out ASAP help!:)


  • SWEI
    SWEI Member Posts: 7,356
    What's under the floor?

    any way to put tubing and plates up from below?

    Radiant heating will require a bit less energy than forced air, all things being equal.  You can generally count on a space temp (air) of 3º-4ºF lower, but the BTUs still need to be there to offset the losses.

    http://www.eia.gov/neic/experts/heatcalc.xls will help with the math.
  • Rich_49
    Rich_49 Member Posts: 2,766
    edited November 2013

    1 Kw = 3,414 BTU

    1 Therm = 100,000 BTU

    These are both billing units used by utilities . If 29.3 Kw of electrical energy costs less than 1 therm I think you have your answer .  Where I am in NJ the Kw costs .14 and the therm costs .52 .  So here , in this market my choice would be between 4.10 and .52 . or 8xS more expensive for electric .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • SWEI
    SWEI Member Posts: 7,356
    Don't forget

    to include appliance efficiency in those numbers.  That DOE spreadsheet is really handy.
  • Gordy
    Gordy Member Posts: 9,546
    Electric radiant

    Radiant needs to be planned for.

    If your only options at this point is scorched air or electric radiant, I would opt for the forced air with electric radiant as a floor warming asset to say a bath area.

    To heat solely with electric radiant would cost an arm a leg, and first born at those rates.

    Keep in mind your choice of floor coverings. Low r for radiant areas. If the kitchen is tiled, and the bath use the electric radiant as floor warming in those areas leaving the actual heating to forced air.

    Depends a lot on your expectations here. Is duct work existing or needing redesigned?

    What was there before?

    IF you really want radiant do it hydronically not electrically.

    With hydronics you are unlimited in heat source choices in the future. With electric... Well it's electric.

    Are you wanting AC? If so duct work is in the picture anyway along with air handler etc.
  • SWEI
    SWEI Member Posts: 7,356
    For that small an apartment

    I'd seriously consider these http://www.rinnai.us/direct-vent-wall-furnace before I installed ductwork.
  • Gordy
    Gordy Member Posts: 9,546

    But what about Ac Kurt?
  • SWEI
    SWEI Member Posts: 7,356
    If A/C is part of the requirement

    and the owner of this rental property places some value on ROI,  I would probably recommend a multi-head ductless mini-split like the Mitsubishi CITY MULTI, the Daikin VRV, or the Fujitsu Halcyon.
  • DC_grl
    DC_grl Member Posts: 1
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    Hi everyone. Thanks for your answers. Homeowner again. Just to clarify,

    The apartments are actually 980 sq. ft.  The 600 sq ft mentioned is

    covered area for the heated floors.  Ducts are already in place for A/C and each unit is wired for gas stoves and a gas fireplace in the living area. 

    Because the ceilings are 12 feet high I worry about the forced air

    system heating the upper 6 ft of height while we freeze on the sofa.

    A comparison shows that electric is almost 3 times the price per 1mil BTU’s of gas based on local pricing.

    I have noticed that there are slim (less than an inch

    high) hydronic radiant systems in the UK and Europe which would probably

    work for my renovation.  But I have not seen the equivalent here in the

    US.  Does anyone have knowledge or experience with anything like this?

    It seems I can use a boiler and slim tubing to heat my property, if I could locate them.

    I am considering tankless hot water.
  • Gordy
    Gordy Member Posts: 9,546
    All kinds

    Of over the top sandwich radiant.

    Warm board r


    Roth panel

    Quick track wisbro

    Or make your own plywood sandwich sleepers.
  • SWEI
    SWEI Member Posts: 7,356
    electric is almost 3 times the price

    a heat pump produces 2-3 kW of heat for every kW of electricity that it consumes.  The exact number depends on the particular heat pump (more expensive models generally have higher efficiency) and the outdoor air temperature at the time.
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