Doing a possible whole house remodel and would like to do radiant floors. I tried to search for tube size and spacing, looking for 3/4" tube spacing, but did not find anything. Maybe some can comment or help... House construction would be as follows: 2x4 walls, 3" closed cell spray foam, 3/4" t/g sheething, vapor barrier, 3/4" foam panel, and insulation backed siding. Subfloor on one level would be 3/4" t/g with 1/2" ply on top, other floors 3/4" ply only. I am wondering if I can run a single 3/4" tube in each bay (16" centers)with aluminum panels? Has anyone heard of or done any work with 3/4" under the sub floor that has some advice? Thanks for the help.

no, do not do that. it is a far more difficult install and is inferior by any measure to double runs of 1/2" or 3/8" per joist bay.

there is never a good reason to run 3/4" in a joist heating application. there are reasons, but never good ones.

Thanks Rob, any comments on the 1/2" tubing with extruded panels... What will be the deal with noise using extruded panels and what tubing would be best?

1/2" or 3/8" with extruded panels is the best joist system you can do.

I can't comment as to every combination of tubing and plates out there. we use Mr. Pex and thermofin and the noise issues of the distant past are just that. there may be other tubing/plate combinations that are still noisy though.

Rob is right!

But, I have used a combination of Thermal-Fin extruded aluminum heat transfer panels and nearly every PEX pipe available for sub-floor radiant heating systems here in Minneapolis (including 3 manufacturers of 1/2" PEX in my own house) without a squeak. Naturally, nearly all of our radiant floor designs and installations incorporate weather sensitive controls.

I would not trust radiant floor heating designs that incorporate bare PEX, of any size, between floor joists and the use of 3/4" PEX for anything short of snow melting driveways should be seriously questioned, as Rob suggests.

I have checked out the extruded panels wirsbo and c chanels...any deburring with the Thermal-fin and what about the size of screw holes as I have read that some need to be drilled out?

Thanks for the help.