While we wait...
Here is a slide from the Duluth presentation (also Heatspring), that is an amazingly clever way to do radiant heating:
This has many of the advantages of easily-constructed floor heating, but the radiating surfaces are in front of R-5 (.75" x R-6.7 poly iso), which assures that a higher percentage of the heat energy will be driven in the desired direction. I had wanted to do something like this for my back room floor, but finding an insulating material that could withstand floor-loading, and be 3/4" thick (much less being foil-faced) was a monstrous task.
This plan pictured above uses 3/4" board, which will assure that the aluminum heat spreaders will not 'bottom out' and conduct heat in the wrong direction.
Of course, 1" foil-faced insulation would work just fine, and is easily found as foil-faced poly-iso.
However... I did a search for 3/4" foil-faced foam and located
THIS_STUFF, which is a poly-iso with fiberglass reinforcing in the poly-iso core, and faced, two sides with foil.
It is interesting also that it's compressive strength is 25 psi. I used some Dow Formular 150 (15 psi) in my kitchen walls, which seems really dense to me... it seemed almost good enough for floor loading, especially when the load is distributed by the floor covering.
So, 25 psi seems really intriguing.
I was also looking at a similar Firestone product with 20 psi compression. However the Firestone product did have a note which read:
For requirements greater than 20 PSI, phone Firestone’s Estimating Services Department at 800-428-4442
Could open very interesting possibilities.
-AC