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Small Radiant Floor Heat System

jackleybr Member Posts: 2
Hi, I'm currently building a family room/mudroom addition on my house and Im doing research on the design of an In-Slab radiant heating system. The space I'll be heating is only 320 SF with a heat load of 6400 BTU. Ive had a hard time nailing down the heat source to such a small system. RIght now the rest of the house is heated by mini split heat pump units so there's no form of hot water heat to tap off of. My first question would be does this plan make financial sense factoring in the cost of all the components, heat source, operational efficiency, etc? Also, being such a small system for somewhat accessory living space, are there any recommendations for a heat source? Some of the options my plumber and I came up with are as follows: Installing a propane fired tank water heater for the potable hot water in the house and then using a heat exchange plate, pumps, mixing valve, etc for the radiant system. Another thought was simply a small point of use electric tank water heater used specifically for the radiant system. I woud love some advice from some experts who have experience with small systems like this and could maybe speak to the operational costs of different heat sources.

Thank you.


  • MikeG
    MikeG Member Posts: 169
    What type of floor surface or covering? If a mud job what about one of the electric floor mat systems, or if set on hot water maybe a small electric boiler with all the other components. How about something in floor and also ceiling. I have a small utility room with copper under the concrete and tile floor and pex with plates in the ceiling, nice sandwich effect.
  • HomerJSmith
    HomerJSmith Member Posts: 2,406
    Either of your plumbers suggestions would work. It is basically the cost of each system + cost of operation.
  • HomerJSmith
    HomerJSmith Member Posts: 2,406
    edited March 2018
    Be sure and prevent slab edge loss and backloss with the infloor sys.

    Choose you tube layout, carefully, as to design type (loop, serpentine, etc.) You want the hottest supply temperature against the exterior walls and the cooler flow toward the interior.
  • jackleybr
    jackleybr Member Posts: 2
    Thanks for the comments. The piping will be set 2" +- into a 4" concrete slab with porcelain tile for finished flooring. 2" foam insulation under slab and turned up the side as a thermal break. Electric heat cables are always an option but I was steering away from them because of the cost to run that type of heat constantly. Ive looked into electric boilers a little bit, and we also have been talking about a propane fire combi boiler with an indirect holding tank for the heating loop. My problem is the more research I do, the more options come my way and its tough to know whats going to be the best fit (cheapest to run) until its too late. My other option is to put a mini split on the wall and ditch the whole radiant idea...

    Thanks again!
  • Brewbeer
    Brewbeer Member Posts: 616
    Is the fuel cost different for electric in floor cables vs an electric boiler? Seems like the cost to operate would be the same.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg