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best radiant sys under tile

jp_2 Member Posts: 1,935
for one, I like dan peel's idea, gypcrete over pour up to tubing, then tiling. of course the tile people don't like that idea. I'm also considering the thermal floor, quick trak or rehau plywood/Al systems -non subfloor systems, seems lots to choose from. though you still need a tile backer for these systems as I understand.

if the check was blank, what system would you opt for?
320 sq ft remodel. not found of high mass floors though.

thanks jim


  • hr
    hr Member Posts: 6,106
    What's the load?

    10, 20, 30 BTU's per square foot? Do you have a boiler currently? Does it have a radiant temperature zone? What's the BTU size of the boiler? Multiple zones if it is currenyly hydronic?

    Guessing a 15 btu/ sq. ft. load that's a mere 4800 BTU/ hr. load at design. Less than that most of the year :)Pretty small load!

    Depending on the room, intended use, and answers to the above you may consider some electric mat or cable? Thin set it right onto the floor, cement board over it and connect to a wall stat. You can even use a setback stat with a low mass electric system.

    I'm a fan of all things hydronic but still find electric radiant fills a "small system/load" market.

    If, by god, it has to be hydronic :) the load, floor covering, amount of height to give up, and intended use of the room would help me decide which installation would be best. Lots of choices, as you well know, give us some more data to narrow down good options.

    hot rod

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  • jp_2
    jp_2 Member Posts: 1,935

    first off, from improper internet learning I installed 3 rows 6"o.c.on outside walls(good) & about 12"o.c. mid room(bad). then hand mixed 1 1/4" gpycrete over top.
    this is an old utility room on the end of a ranch, 3 outside walls, lots of new windows. this summer I tore gpycrete out, my expense. floor had cold spots and I rushed the gypcrete, too uneven.....
    but from my mistakes I'm learning a heck of a lot, and the customer is very understanding.

    last winter I recorded about 20btuh/sq ft loading. wasn't that cold though, so off hand maybe figure 25-30btuh. we saw teens but nothing below, ususally we have a week below zero and several weeks 10-15F. 26Kbtu DHWH was cycling 20 minutes/hr.

    house is nat gas FHA, too far from furnace and ducting is not possible. second farest room is always cold, would be the next canidate for radiant, 200sq ft.
    heat plant is not decided yet,thinking expansion & munchkin. last winter I put in a temp DHW heater & ran constant circ@ 90F.

    I did an experiment with tubing 6"o.c., motar bed up to tubing then tile. heats up quick and even.
    what I'd like to do is use PAP, thin mud bed,good antifracture membrane & tile. tile guys do not like this idea though, they are saying 3/4" above tubing. so I wonder if these plywood/Al systems would react faster.

    customer wants what will work best. floor height is not a issue since intitially i planned for 1 1/2" over all.

    initially folks I talked to about ele. mats said I would need supplimental baseboard. and ele is about 4X nat gas costs here.
    insulation: walls 6",floor 8", ceiling 12".

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