Hi All,

Regarding an underfloor system with aluminum plates:
my subfloor is pierced with all the nails used to secure the hardwood flooring above it. I know plates wont make good contact with the subfloor. I'm wondering if i should use solid plates and get them as close as possible to the floor or intentionally space them and potentially use the finned type to max the local convection. I need about 20 btu/ft2.  My calcs are providing this with 130F supply. I just don't have any data on the finned plates to see if it's feasible.

Grind the nail points to get the aluminum to make better contact with the subfloor. With extruded plates it's less total area, fewer nails to grind, but more expensive plates.

Convective heat exchange is very limited compared to even modest amounts of conducted heat. With radiant floors getting the heat out of the tubing into the heat spreader is the biggest problem it solves and even with so-so floor contact the rate of heat transfer to the floor would be better than convecting fins dangling off tubing. I doubt you'd get anywhere near 20BTU/ft^2 out of it @ 130F water temps with convective type coupling.

Ok, thanks. I'm wondering if there are some long handle flush snips that would work better than grinding.

Grind, you'll be glad you did. We haven't used suspended or staple-up PEX for sub-floor radiant floor heating in about 20 years, but we see many systems like that here in Minneapolis. Very few of them work to expectations.

Naturally, no one knows what will work until they perform a proper heat load analysis.