Radiant heat over existing floor

Hammer1245it

i’m putting a radiant floor over a existing floor with a crawlspace below. I’m wondering if a half inch insulation would help I have room to raise the floor ice almost 2 inches at one time it was a porch. I plan on putting pieces of five eights plywood for half inch pecks and leave the track for the pecks then put quarter inch cement board and tile on top.

hot_rod

1/2” is only R2.5 can you get more insulation below the floor? 6” batt at the very minimum

The tube needs to be in good contact with the floor covering layers, the cement board for example

Have you done a heat load calculation for the space

EdTheHeaterMan

Is there a way to get in the crawlspace below? I would consider adding R-13 or R-19 fiberglass insulation below the existing floor before you attempt to do anything else.

Is the floor getting raised the 2" regardless of where the insulation goes? If can you Just staple the PEX to the existing floor then adding thin pour Gyp-Crete® over the existing floor. That will place the tubing in direct contact (no air gap) with the tile surface

DCContrarian

For a setup like this you should be thinking either 8-10 inches of insulation in the floor, or insulating the walls of the crawlspace.

I imagine your floor is cold now. Installing heating in the floor without insulating properly is a very expensive solution to that problem.

Is there plumbing in the crawlspace? If so, insulating the floor may cause it to freeze.

psb75

Crawl spaces are almost always problematic. Best to treat it as "conditioned space." Insulate the exterior walls of the crawlspace. Put down vapor barrier. Do not allow the radiant floor to radiate downward by using proper amount of insulation underneath and around the edges of the room. I don't recommend fiberglass. Use rock wool, EPS, or icynene foam Best to have tubing in direct contact with the "mass" (ideally, IN the mass) that is radiating heat upwards into the room.