Radiant tubing

Unknown

plates make a pretty big difference.

J K STRAITIFF

WHY DO YOU NEED AN INCH OF AIR SPACE UNDER PEX RADIANT FLOOR TUBING?

Brad White_27

Reflectance.

The assumption is that you have a reflective radiant barrier below the PEX (PEX tight to the underside of the deck of course, and one would assume R-19 insulation below the radiant barrier).

The concept is called radiant flux, the converging matrix of infra-red rays. Simply stated, they need room to bounce around a bit. If you were to place the insulation tight to the PEX, with or without a reflective surface, the tendency would be to isolate each tube unto itself. The effect may show up as "striping" or distinct warm then cold spots on the floor.

When the inch of space is provided, the IR rays bounce around and spread out, giving a much more desireable even temperature across the cavity, hence to your floor.

Film at 11:00

Brad

Unknown

Actually, it depends on what you're installing.

If you are suspending tube from the subfloor, you are creating an air plenum and you need a 2" airspace to allow air to form small convective loops. Reflective insulation is not necessary.

If you are not suspending the tube from the subfloor, and are using plates, then the airspace is not necessary. doesn't hurt either, really, but it's not necessary.

J K STRAITIFF

WHY DO YOU NEED AN INCH OF AIR SPACE UNDER PEX RADIANT FLOOR TUBING? I HAVE NO CRAWL SPACE. 2X10 JOISTS WITH CAVITY FULL OF INSULATION (R30). 1/2 SUBFLOOR 3/4 SLEEPERS. I PUT DBL BUBBLE IN SPACE BETWEEN SLEEPERS TO FORCE CONTACT WITH THE PEX TO THE 3/4 SUBFLOOR AND 3/4OAK FLOORING ABOVE. I WILL NOT HAVE A 1 INCH AIR SPACE DIRECTLY BELOW THE PEX. WILL I GET ENOUGH REFLECTANCE TO AVOID HOT AND COLD SPOTS WITH THE 3/4 SPACE ON THE SIDES OF THE PEX?

Unknown

You have an inch and a half of wood over the pipe? You probably won't get heat striping, but I'd wonder if the system will keep up. That's a pretty weak method you're using to fight that much wood. Reflective insulation is not going to help that much in this type of install.

Kniggit

betterh then what I have and mine heats. granted mine uses plates. under the origian slab, ut I only used reflective thenR-22 below that.