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New house Radiant setup

Hello all,

I had a radiant heat(mostly basement)/Unico HVAC(main floor) system designed for my new construction by a pro(he is long retired now). I am in Minnesota.

My project has been progressing extremely slow. Along the way, I decided against Unico and went with traditional HVAC, which covers the main floor (with code minimum supply and return in the basement).

For the basement, I did follow his tubing layout plan before the concrete was poured and left it at that.
Now I want to pick up from there and finish the radiant heat setup all the way. I need help tweaking the plan slightly(I will explain below) and need help figuring out the components of my setup.

Part of PEX layout(basement) that is already done:
I installed the PEX in the basement using this layout:

Part of PEX layout(main floor) that is not done and needs design adjustment:
Radiant heat was also specified for Master bath/bath 2 on the main floor.

desired plan for main floor:
In the image above the area marked for Master bath and bath 2 were combined making the master bath slightly larger. I am thinking about doing a staple up application,
In addition, I would like to do a staple up application for the foyer area(highlighted in yellow and circled) which is only 70 sq ft but will have tile floor.
Heat load:

The Plan:
The plan is to have the equipment in the mech room and main supply and return run all the way to the manifold closet in the basement.
What should the manifold setup look like?
How do I tie the master bath and foyer into the setup?
Do I need 1 manifold(4-loop) for the basement and 1 for the main floor(2-loop)?
Likewise, should the basement be 1 zone and the main floor be a separate zone?
What heat source makes sense? how many BTUs The DHW is already installed and radiant will be on it's own and the loads are really low.
I will have more questions but I will pause for now so not to have information overload.:)
And I really appreciate any insight in advance.


  • hot_rod
    hot_rod Member Posts: 21,874
    looks like you need a two temperature system as you range fro 80nSWT in the slab to 118 in the bathroom. The staple up zones will need warmer SWT, of course.

    It is always a bit of a challenge to mix two systems, the HVAC forced air with radiant. If the HVAC warms the space the radiant may never kick on? If the entire home had both HVAC and radiant you can use two stage thermostats.

    You may want a buffer tank if you plan on zoning the bathrooms and entry as separate zones. Or a tank type heater like this HTP Pioneer, a 55 gallon tank style hydronic heater. So run the tank at 120 all the time, mix down to 85 for the low temperature zones with a thermostatic mix valve.

    If the basement bedrooms are not used often, I would zone each one, the family rooms as a 3rd zone.

    You can always hide extra thermostat wires in the wall in a box behind the sheetrock, if you wanted to split the family room zones later you have the wire available.
    4 conductor wire to every thermostat if you want to use stats like the Ecobee, HW, etc. you need a 24V power plus the 2 switch wires.

    I like these Uponor dual stats for bathrooms as you can maintain a warm bath floor year around, even when AC runs. Set floor temperature to 80- 82F to always keep the floor warm.
    Run a pex tube below the floor and to a regular single plastic switch box, where you want to mount the thermostat. This allows you to get the floor sensor out for repairs. Plus all the thermostat wiring is in a box for more work room.
    Purge valves near the heater so everything purges near a floor drain, no need to purge at the manifolds.

    ECM circulators on delta P mode, Grundfos Alpha 15-58 for example.

    Piping could be this simple.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • timberwolf78
    timberwolf78 Member Posts: 2
    I really appreciate the detailed response. Your comment on radiant potentially not kicking in because of the space being warmed enough is making me rethink the decision to use radiant on the main floor. And it's actually something I have been pondering if it's worth the complexity and cost.
    Sticking with radiant in just the basement makes things pretty straightforward.
    The heat load is less than 12000 BTUs and the space won't be used often.
    If I were to go that route, what are your thoughts on using something like https://www.menards.com/main/plumbing/hydronic-radiant-heat/radiant-heat-boilers/stiebel-eltron-hydro-shark-reg-electric-microboiler/sh3-07/p-1444433731813-c-8519.htm as the heat source?
  • hot_rod
    hot_rod Member Posts: 21,874
    I have not used that brand, but I have used the Electro out of Minnesota
    The M2 series has outdoor reset, and true modulation. The 5 kw is adequate for the load you have


    A budget system would use a 40 gallon electric water heater, those are 4500W🧐 no controls however so it would run all the time unless you cobbled together a relay to handle the 4500W resistance load.

    I do like floor heat in large tile master baths. If you ran the heater at say 100F you could run. The slab and bath at one temperature. Put the tube 6” on center instead of the 9” noted in the design for the needed output at the lower SWT.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • GroundUp
    GroundUp Member Posts: 1,868
    X2 on the Electro boiler, and I'd agree with the assessment of possibly only using the basement radiant for simplicity's sake. Those Menards setups are neat in theory, but they use a tankless water heater rather than a boiler and frankly, you get what you pay for. I offer a similar DIY system (or installed, if desired) using Electro boilers and each is custom built to the application rather than "one size fits all" like those are. I'm located in MN as well and would be happy to discuss your project if you'd like.