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Need help confirming design

jlehrman Member Posts: 8
I'm in the midst of planning to use hydronic radiant system for our entire house. It's an old-house that we've added an extension (~50%) to and essentially gutted. Each floor is aprox 1050sqft.

We going to go with warmboard-R for the ground and second floor. For the basement we want to stick PEX in the slab due to the cost savings. Unfortunately, Warmboard is asking a huge premium to include the basement in their complete package, so we've decided to use them only for the panels but that means we loose out on their extensive design.

We're in Montreal where it gets pretty cold. However, we'll eventually have a mini-split (inverter works down to -25C). We'll hopefully also have a legal fireplace that can emit heat on the ground floor (which is open concept). I'm not too worried about doing a proper heat-load but it would be nice.

In the basement, ~650sqft has a slab that's been cut-up a bit for plumbing. We have about 7' headspace but I'm tall (6'4") so, I want to be careful about loosing too much. It's not too level. The rest of the basement (~350sqft) is new and the slab hasn't been poured yet. The contractor is planning to have a pump truck to pour the slab and cover the piping trenches in the old slab.

I want to embed PEX in the new slab (with insulation below). What's the best approach for the existing 650sqft? I want to ensure it's relatively level. Can I pin PEX directly to the existing slab and pour a thin/minimal layer on top? What about spacing of the PEX? Would 6" loops be too much? I am concerned about cost but I also want this to be done properly. I'll likely be laying the PEX myself.


  • Hot_water_fan
    Hot_water_fan Member Posts: 1,799
    edited August 2022
    Does that portion of the basement need in-floor tubing? A panel radiator or two would be an easy substitute. There will be limited benefit to basement in-floor heating since the heat load will be low down there.
  • jlehrman
    jlehrman Member Posts: 8
    I didn't think of that. Can panel radiators be integrated into the same system (boiler, etc...) as the floor heating?
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,799
    I didn't think of that. Can panel radiators be integrated into the same system (boiler, etc...) as the floor heating?
  • hot_rod
    hot_rod Member Posts: 21,878
    Depending on how you use the basement, kids playing down there for example. it would be nice to have radiant. Ceiling radiant is a close second, panel rads maybe the next choice. The flexibility of hydronics is you can blend most any heat emitters.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,600
    edited August 2022
    jlehrman said:

    I didn't think of that. Can panel radiators be integrated into the same system (boiler, etc...) as the floor heating?

    Here is a text that you may find helpful. Page 24 addresses your question about 2 temperatures, since your panel radiators may need a higher temperature than the floor heat. http://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf
    The entire booklet is written with the Non-Engineer in mind. It helps to get the basics in Hydronics to be easily understood by folks like us. Sort of a Boilers for Dummies book.

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics