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Warm radiant floors?

In another thread, someone mentioned installing radiant heat in a floor because the wife would appreciate warm floors. I wonder about this because my downstairs is heated with copper tubes in a slab at grade. I have a mod-con with outdoor reset pretty aggressively adjusted to give just barely enough heat to compensate for the heat loss, and it heats very well. But the floors are rarely what I would call warm. I do not know the spacing or lengths of the tubing. There are five circuits there, and there seems to be one for each room.

Today would not be a good day to run tests, but that is what I did.. The heat did come on for four hours today, must have been very early in the morning. The floors are about 71F, and with the current outdoor temperature, the boiler would have been supplying 75F water to the slab. The concrete driveway outside (no snow melting) is about 60F and the outside air is 55F.

While I did not write down the temperatures in cold weather (there really was none this year), last year it got down to about 9F a couple of times (only at night) and I think the floor got up to 80F or a little higher and that might have been warm.

Back when I had my old boiler (old GE: not mod, not con, no reset), the floor did get uncomfortably hot at times. But never with the new boiler. I usually cannot tell when it is running unless I look at the thermostat that keeps track of the hours and minutes it runs each day, and it remembers what it did for the previous day.

So is it realistic to expect warm floors except in the very coldest days? It seems to me this would work only in floors where there was an insufficient amount of tubing in the floor, or where the heat loss is so great as to require quite high water temperatures in the floor. Is that right?


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    You are correct JD...

    I can't tell you how many times I've gotten a call in the middle of the Summer from the consumers wife wanting to know why her floor wasn't warm....

    Honestly, the BEST place for warm floors is in the one (hopefully) place that you will find wet naked people, that being the bathroom.

    I had an agreement with a top of the line home builder I use to work for. We'd install hydronic radiant floors through out his beautiful homes, and he would also do an electric radiant floor in the bathroom, using a programmable thermostat control. This way, the consumer was USE to having warm floors in the SUmmer, but only in the bathroom, where they are needed the most.

    I've said this before, and I will keep saying it until the words soak in. Radiant floors are not the only way to deliver a good human comfort experience. I think we've oversold the warm floor concept, and have stepped right over less expensive means of being able to deliver a good radiant human comfort experience. There are PLENTY of other surfaces in which to install a heat source (take your pick of fuel sources) and deliver good radiant comfort. I personally hold RIchard Trethewey responsible for the ongoing radiant floor revolution. If he hadn't shown up on This Old House with a roll of PEX on his shoulders, this industry would still be trying to move forward. God bless him, but I still wonder what our world would be like, if he'd said" Today we're going to install a radiant ceiling comfort system..."

    None of the customer who have radiant ceilings ever complain about their comfort levels...

    None of the people with radiant panel heaters ever complain about their comfort levels...

    And honestly, the people with radiant floors never complain about their comfort levels, but they want to know why their floors are not warm when the heating system isn't on... I guess it really comes down to properly educating the consumer, as you said, expect warmer floors the colder it gets outside, and less warm floors the warmer it gets outside. That's the way it is supposed to work.


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    Jean-David Beyer
  • Gordy
    Gordy Member Posts: 9,546
    To add

    That the better insulated the home the colder it will have to get outside to realize those warm floors. The tighter your tubing centers the lower the water temps play a role to a point.

     There was a day when fuel was cheap, insulation did not matter, and no one complained about to much heat they would just open a window.

     Personally I really like the sun bathed feeling from a radiant ceiling as I'm relaxing in the recliner, or laying on the couch cause my feet don't touch the floor.

     This winter in tha midwest was a mild one. Kind of one long shoulder season for radiant heat of any kind.

  • Tim Potter
    Tim Potter Member Posts: 273
    Radiant Panel Heaters ???

    Mark, would you clarify for me what you are referring to as a radiant panel heater. Are you talking tubing in some kind of aluminum coated wood panel that has a grove for pex, & is installed under the sheet rock, or a modern version of the cast iron radiator, or something else.

    Wow, what a lack of snow in the mountains this year, quite the change from last year. Now I'm really concerned about Fire this summer. Hope things are well in your world.

    Thank You for the info:

    Winter Park, CO & Arvada, CO
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    All the above Tim...

    Radiant walls, made with Warmboard work fantastic.mradiant ceilings using that method, or as you point out, self built emitters work well too.

    I took a tour of the NREL facilities in Golden a while back, and they were using ceilings that were 20' off the floor for heating And cooling. Blew me away.

    It's dry in the Heeney drainage as well, but they are calling for as much as 20" of the wet white stuff this weekend...

    The ice came off of the lake 3 weeks early this year. In fact that is the earliest the ice has eve come off. Global climate change... (warming in THIS case)


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