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Thermal pics for radiant under oak floor with stamped heat transfer plates "pressed and insulated"

ekubec Member Posts: 12
edited January 2023 in Radiant Heating
Finally got around to a good use for the Inkbird Sous Vide and created a small radiant floor for testing.


3/4" Subfloor OSB
3/4" Oak wood (Installed with wood screws)
1/2" pex al pex
0.5mm thick x 24" long x 12" wide sheet aluminum
2.25" of Extruded Polystyrene
Superlube heat sink transfer grease.
7/16" OSB
Deck screws


I don't own flooring staple/nail gun, so screwed oak flooring into subfloor with wood screws. I only covered half of the 1 foot by 2 foot area so as to see the delta between subfloor and oakfloor temperatures. From underneath, I painted the underside of the subfloor with latex. Then installed the aluminum heat transfer sheet as follows: First I applied thermal grease to the entire subfloor facing face, including the pex channels, going a little thicker on the latter. Next came the "composite" as I brought the aluminum sheet, pex, sub floor 2.25" of ext poly, and 7/16" OSB all together in one tasty radiant sandwich. I "pressed" the sandwich together with the heavy duty torx big screws, going from the 7/16" osb on the bottom "up" and into the subfloor OSB. You can see from the pics that I left some of the bottom exposed as I was interested in seeing the temperature deltas.


InkBird 1000 Watt Sous Vide cooking immersion circulator. Worlds smallest boiler! Comes with its own circulator!
5W 'cat water bowl' pump. In this set up, it puts about 1/2 gallon per minute through the system.

Testing equipment:

Flir One first gen
Spot infrared thermometer gun
Meat thermometer


I did this in my cold basement (about 62 degrees). I have run two tests with supply water temperature of 120 and one of 125. Once the system had been running for a couple of hours, I measured with both infrared cameras the surface temperature of the test floor as well as the ceiling and walls around it. The surface temperature was around 74-76, and the delta between that and the surrounding surfaces ranges from about 11-14, mostly being about 12. Interestingly, my measurements don't confirm that running the SWT at 5 degrees more (125) vs 120 correlates with a higher delta, and thus higher BTU per square foot. But they should. So I need to do some more testing.

Next steps:

- I wanted to see if I could hear any noise when the system went from the test floor being 60 degrees to having 120 degree water in it. I left the cat fountain pump turned off while the inkbird brought the temperature to set point, but discovered the delta of the water temperature in the system created a natural flow, so the tubing was warm and flowing before I even turned the fountain pump on. So next, I will pull the tube out of the water while heating to set point, then 'shock' the system with 120 - 125 water

- I am curious to see what the surface and delta temperatures are with the same set points 120 and 125 but upstairs where and when the ambient room temperature is 65-68

- I want to see what the surface temperature with same conditions but with carpet pad and carpet would be.

Anything else anyone would like for me to test?

Pics here: https://photos.app.goo.gl/z7fYbM9h8UhkxWRu8


  • hot_rod
    hot_rod Member Posts: 22,483

    Some 4x8 test panels I did years back. Left 1/2 of each has carpet, no pad. The carpet will spread the heat out better, but also lessen output.

    From the front
    WarmBoard with pex, ThermoFin with 1/2" copper, ThermoFin with Uponor pex, rubber tube, suspended pex, stapled rubber. 6" fiberglass batts below when testes the 1/2 gpom flow

    Rubber tube and suspended pex are least powerful transfer examples. Although the staples on the rubber tube transfer well :)

    Warmboard and ThermoFins are close, considering the Warmboard is 12" OC. And the power of the aluminum is important as you see where I routered across then WB and cut the aluminum.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream