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Tiny House Hydronic Radiant in floor Heat Source Option Question..

Looking for Ideas or options & comments on heat source for Hydronic In-floor heat...
Here is what I have, 12'x12'x12 Tiny home (17285 CUFT) R-21 walls and floor, R-38 Ceiling. 51SqFt Triple pane windows, 1-3/0 steel insulated man-door. Tubing is 1/2"pex on Reflectix covered subfloor 6"OC then covered with 1/2"Durock cement board, will have laminate over that. I would prefer Oil for the Hydronic heat but TOYO on demand seems to be only option here in Alaska (almost $3K). Propane is an option but I have had trouble in the past when its 40 below. Considered Electric but don't think that's viable especially in winter if there is a power outage. Will have off grid solar power backup.. Ideas?


  • Jamie Hall
    Jamie Hall Member Posts: 23,446
    How much heat do you really need in that place? I suspect the smallest oil boiler is going to be overkill... LP at 40 below is going to be trouble. And electric isn't an option for heat -- particularly off grid and in an Alaska winter.

    I presume wood is out? My preference would be a small wood stove... like the Jotul F602V2.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,337
    Hi, I agree with Jamie. If you search for marine wood stove, you’ll find some stoves that might be a good fit for your application. I’d just make sure that what you get can use outside air for combustion.

    Yours, Larry
  • bboepple
    bboepple Member Posts: 6
    Yup wood is out, did that my first 20 years her in Alaska, takes up too much room and needs constant attention. Want to be able to go away for a day or a month and not worry...
  • Mosherd1
    Mosherd1 Member Posts: 70
    edited January 2022
    If your wanting to go with oil, would an oil fired water heater work with anTaco Iseries Outdoor reset mixing valve?  Run the tank up to 180 then don’t start the burner again till the tank cools down to 120 degrees.  It would probably only run a few times a day, if that much. The biggest issue with that would be space, you don’t have a lot to start with and then to lose the square footage from a tank style water heater. 
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,886
    Like Jamie said, why bother with in-floor heating with a house this small? The wall insulation is pretty low, some more rigid insulation could really improve the heat loss and is 100% reliable.
  • hot_rod
    hot_rod Member Posts: 22,262
    I build an 8X20 tiny home on wheels a few years back, here is what I learned after running the load calculation.

    The available floor space may not be adequate to cover the load. Any beds, cabinets or built in subtract out of your floor square footage for heat emitter.

    I tried to keep as much as possible tables, cabinets etc from covering the floor, suspended them.

    I scoured the world :) looking for small output boilers.

    Turns out the trucking industry has about the perfect size "coolant heater" for those size loads. They can be fired with diesel or gasoline. They have been around for many years as both heaters and engine pre-warmers via the engine coolant.

    The RV industry has some nice LP fired tiny boilers similar to these that I found in Germany, fairly $$ however.

    Those mega dollar bus size RV sometimes have radiant floors powered by there Webasto heaters.\

    I think Winnebago uses diesel powered boilers out of Oregon,in some RVs. Chat room talk indicates they can be very finicky at altitudes, soot up and lock outs unless you have a high altitude kit. But then sea level burn becomes an issue.

    Truma is another brand with some interesting duel fuel versions electric element and gas or diesel.

    I ended up with a Thermo 2000 mini electric boiler. A 30A circuit would power it.

    In my 10' truck camper I have Cubic mini wood stove, welded in Quebec. Great for heat and cooking.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • delcrossv
    delcrossv Member Posts: 748
    edited January 2022
    +1 on Webasto diesel heaters. I've done a couple of marine installs of them about 15 years ago using panel rads. Seems they've really stepped up their game for the RV market.

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.