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Questions on DIYing a radiant floor

Jim R.
Jim R. Member Posts: 58
The next project has me removing about about 1000sqft of hardwood in rough shape and putting down 1/2" ply to help stiffen and quiet the subfloor (planks). On top of that will go 3/4 hardwood. We're also losing our kitchen bboard heat since a wall is coming down and cabinets are being added. There are no good options to relocate heat, probably have to use toe-kick heat exchangers and a panel rad somewhere.

So... if I'm doing all that, does it make sense to run radiant instead? I'm planning to do most of it myself except for the hardwood install. How much of radiant work is DIY worthy?

We have slab radiant in the basement, it's quiet and heats up good. Set and forget. We don't have any fancy controls on the boiler (constant circ, outdoor reset, logamatic, etc) -- just circs, zone values, and a mixer.

Some questions:

- Was thinking to get a 6-7 port mixing manifold. Mixing valve, circulator, and manifold all in one. About $800. Each port has an attachment to act as it's own zone valve. Conveniently enough, it's fed with 3/4" and there is an unused 3/4" stubout on the boiler for future use (supply and return). I'd probably get my boiler guy to install but does this sound like a solid plan? Those manifolds any good? Califfi was one brand I looked at. Utility room is tight, this looks like it will save on space.

- Planning to go thin gauge omega plates at 8" centers, 1/2" pex. I need to refine heat loss calcs but guesstimate is that's where I will end up. I especially want QUIET HEAT. I don't want to trade the clicking crackling baseboards for creaks elsewhere. How do the thinner plates (.018") hold up? I know they shouldn't touch, but does screwing down one side vs. both sides make a difference? Use construction adhesive with the pex to limit movement? Thinking to install upside-down U with plates under the sleepers.

- Should I be looking at hardwood thinner than 3/4"? Just seems like a lot of wood to heat but my basement concrete slab heats just fine.

- Should I plan for fancier controls on boiler, like outdoor reset or constant circ?

- Looked at some prefab products like warmboard-r and heatply. They break the budget. 2-3x the cost. Hoping by the time I start woods comes down. $50 for a 4x8 now!!

Any tips (even if you're talking me out of it) are appreciated.


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,100
    edited March 2021
    I did my own under-floor tubing in a crawlspace. I used the aluminum plates. Then I had spray foam insulation installed to cover all the tubing and plates. I am using a Mod/Con boiler without any mixing valves. The boiler limit is set for 120°F and the return water is about 110°. I am using a room thermostat to regulate the room temperature. It is working great but I do hear some mild creaking noise from the PEX expanding. Nothing like the tick, tick, tick of baseboard heat, but it is not totally quiet like the zone that is in a concrete slab. on the rear addition.

    The bottom line is, I could probably sleep thru the very mild creaking expanding noise if it were in the bedroom, but the bedroom is in the rear addition on the concrete slab.

    Hope this helps.

    Yours Truly,

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • hot_rod
    hot_rod Member Posts: 19,924
    The thin flashing thickness plates have a tendency to "oil can" make that pop sound as they heat and cool. Some squeaking is also possible as they do not grab the tube as well as extruded plates. Tube with the EVOH b arrier on the outside is known for squeaking. Rub the tube against itself and you will hear the noise.
    Creaking sounds are more related to how well the floor and subfloor has been fastened.
    The key is the lowest possible SWT to minimize all these "movements"
    Personally the cost difference for your type of install,Id go extruded.
    Those thin plates can work when sandwiched between multiple layers to keep them from squirming.
    Thin, engineered hardwoods do best with radiant heat, less R value, less potential to shrink and expand, less lumber to buy :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • kcopp
    kcopp Member Posts: 4,261
    How about installing a panel radiator to replace the hot water baseboard.
    A lot less cash and a lot less work to install.