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Community and Q&A

Hydronic heating vs minisplit heat pump

pplp | Posted in Energy Efficiency and Durability on

Over the years have been collecting various items for a new build.   Keep seeing comments better to go with the mini split heat pump (thermo climate zone 4)  I already have many components for the in floor radiant.  So the question.. why would I not go with the comfort of in floor.  or just sell it all and go with what some consider more energy sipping mini split hp.   I am shooting for 1 ach/50pa.  Am also looking at DIY solar panels, or may opt for evacuated tubes 1 set 20 and 1 set 30  tube.  These should run somewhere around $1000 total.  Since In going to install 5kwh  worth of solar PV  figure I can load dump to the 80 gallon water heater.    2100 sq ft  build with 12 inch double stud wall and 16 inch I joist.  Vented 3/12 shed roof pitch.     Seems like if one goes looking for information you can find huge amounts for areas in the cold north and some small amounts of those who are down on the gulf coast in zone 1 and 2

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  1. user-2310254 | | #1

    Hi PPLP,

    I'll throw out a comment to give you a bump. Like you, I loved the idea of installing in-floor radiant heat. But the more I researched the topic the more convinced I became that it was a big waste of money (at least in my climate). If you are building an energy efficient home with high-quality windows, it is much easier and cheaper to achieve indoor comfort using a mini split. That said, I might consider installing electric floor heat in a master bathroom to avoid having to step on cold tile.

  2. pplp | | #2

    Good points that I have been thinking about. What I am considering is using 1 inch pex al pex set on 12 inch centers. So actually not a lot of pipe and actually likely wont need to run the temp very high as I am in zone 4 close to zone 3 Around here the hdd range between 2500 to 4200. Really am looking at low ach . As I mentioned looking to be energy efficient.

    1. user-2310254 | | #3

      You might want to read this article (

      In Zone 3/4, AC is usually desirable. With a mini split, you have a system that will heat and cool while delivering great efficiency.

  3. Expert Member
    Akos | | #4

    Floor heat is good for taking the edge off troublesome ares. Tile surface, rooms in overhangs or larger windows. You can do this for much less money and very little operating cost with electric resistance floor heat.

    Since you already need the mini split for AC, might as well use it for heat, the hydronic system is a redundant add on that is definitely not cheap. Even if you are DIYing it, your effort is better spent elsewhere, the perceived comfort people think of just not that much in a low loss home.

    P.S. I have done hydronic floor heat a number of ways but I have never heard of using 1" pexALpex. I can't see how that could be serpentined inside joist bays, that stuff is almost as stiff as copper pipe.

    1. HFF | | #6

      Hello Akos, you have mentioned this method of spot heating with electric wires several times and I am considering it for under a wall with several large windows. Can you tell us how you detail this with hardwood floors? Is it a single wire and can it, for example, be hidden under baseboard trim? Thank you.

      1. Expert Member
        Akos | | #7

        Standard resistance floor heat mat.

        With hardwood you have to limit the temperature so that you don't warp the wood, but it still can provide plenty of heat. You should size the width of the mat to cover the expected heat load in that area. This would be the loss of the window or the floor if an overhang.

        You can also use standard panel/baseboard heaters, I'm not a fan of the look though. For new install the electric floor heat is not much more cost. There are kits you can install bellow the floors in the basement for a retrofit.

  4. Expert Member
    BILL WICHERS | | #5

    It sounds like you’re thinking of solar water heaters? Most on here will tell you not to bother, it’s usually a better investment to install more PV. You can use the extra PV capacity to operate electric resistance floor heat. Electric resistance will probably have a lower installed cost than a hydronic system.

    I think you mean you’re planning a “5kw” solar PV system. 5 kWh would be 5 kilowatt hours, which would be a pretty small system equivalent to something less than 1kw worth of panels. It’s important to use the correct units with energy systems, especially when you’re trying to maximize performance the way you want to do in energy efficient homes.


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