Radiant Floor Heat Question

[largeitalian1]

Lot of different opinions on this. Ive talked to a ton of people. Better to:

1) Staple pex directly to foam and put concrete over top.
2) Staple pex to foam and put a layer of sand over the top, and then concrete.
3) Attach the pex to the rebar.

My father in law swears up and down that #3 will give me my best heat efficiency. But all the install guys want to do #1 or 2, might just be because its easier.

Thoughts?

 

[UpstateNY]

I did #3, never heard of #2, people do #1 with success. I almost went with #1 but I thought the staples sucked as they didn't firmly hold the pex, I wasn't confident the pex would stay put during the pour, and I don't think an ounce of sand over the top of the pex is gonna help.

Efficiency has nothing to do with #1 or #3, not sure if the layer of sand would inhibit the flow of heat. There's no way I would do it. Put your location in your siggy, you'll get better responses.

My $.02.

 

[largeitalian1]

Apologies. This will be in Bismarck,ND. Frigid winters.

 

[Northislander]

4) attach pex to 6'' x 6'' 10ga. steel mesh sit on chairs and pour concrete slab

 

[largeitalian1]

I am unaware on this method, what are the advantages?

 

[4cyclic]

I did #1 in my shop , worked out great. Then heavy wire mesh over pex.

 

[ctgoodman]

I've always hear the most efficient way to do radiant is to insulate the slab from the ground otherwise you are having to overcome the cold transfer into the concrete when you are heating. I agree attaching the pex to foam may have its own issues but you could also do rebar over the foam to attach the pex to.

 

[largeitalian1]

Yeah I fully planning on insulating under the pex. I am just trying to determine whether to attach the pex to the foam or rebar.

 

[yeldogt]

The few times I have seen lower slab jobs with PEX attached to the foam it was put down and poured .. no other trades around. Staple down is common over wood floors for lightweight concrete.

The 6" wire allows for easy layout and stands up to people walking on it -- They also use a gun for the staple down.

I always use the wire ... makes it easy.

 

[largeitalian1]

Also I should add, this is a floating slab. 5" thick, 18" thickened edge

 

[1938flatty]

Have built two garages in Michigan. Both instales were the same. 2" insulation, plastic holders screwed into the foam with a V on top and the pipe snapped into them. They were about 3 feet apart from one another. Poured 4" concrete over with fiber mesh. No steel in either floor. The first one is 10 years old no cracks. The second one is 6 years old.

 

[yeldogt]

1938 -- You did you PEX 3' apart?

LI1 -- Need to make sure insulation is correct with a mono slab

 

[Northislander]

If you check my post "Is 53" thick insulation under Radiant Slab enough?" further along in this forum the first pics show a radiant install on rebar installed on 8" centers with 6" steel mesh with 1/2" pex attached with cable ties the whole assembly is sitting on pieces of 1/2" plywood during install when everything is done the whole assembly is lifted and put on plastic rebar chairs so the rebar, mesh and tubing is in the middle of the concrete pour. The 1/2" plywood is in place temporarily to make it easy to get your fingers under the bar to lift on to chairs.

 

[1938flatty]

No, No. The plastic holders that hold the pex to the foam were about 3 feet apart. I think the pex was maybe 8"-10" apart. It's been awhile. A family friend who sells and installs the stuff helped.

 

[1938flatty]

I used the red one in the top/center of the picture. The bottom Screwed into the foam and the pex clips into the top.

 

[Gooch]

many studies have shown that the closer the tube is to the surface the more 'responsive' the system will be(quicker temp changes), this would reduce the possibility of the fly wheel effect.

That being said, Mine is stapled to the foam. I don't think it's worth the added labor to not install it on the foam. maybe if you were going to be doing a 6"+ slab.

 

[Dagny]

Staple to foam what if you want to mount something to the floor .

 

[UpstateNY]

No, No. The plastic holders that hold the pex to the foam were about 3 feet apart. I think the pex was maybe 8"-10" apart. It's been awhile. A family friend who sells and installs the stuff helped.

Ital,

The pex near the walls should be 6" from the edge of the wall, all other pex should be 12" apart form each other. Goggle to find some suggested pex layouts. Mine is a 30x40, per the calc I needed 5 runs of pex at 300' per run.

 

[Radix2]

#1, staple down, wire or rebar on top. Gets the metal at least a little off the bottom.

 

[forAK]

#1, staple down, wire or rebar on top. Gets the metal at least a little off the bottom.

^^This^^

Alleviates the need for chairs also. The install will fly by doing the staple method.

 

[Firebrick43]

#1, staple down, wire or rebar on top. Gets the metal at least a little off the bottom.

+2. Torn out to much concrete and the wire is on the bottom nearly always. It amazes me to this day to see a concrete guy standing on wire trying to pull it up with a hook. Whiskey Tango Foxtrot

 

[largeitalian1]

+2. Torn out to much concrete and the wire is on the bottom nearly always. It amazes me to this day to see a concrete guy standing on wire trying to pull it up with a hook. Whiskey Tango Foxtrot

I plan on doing rebar on chairs. Does what you are saying apply?

 

[Firebrick43]

If there quality chairs and you tie the rebar well together where it crosses with wire ties the concrete Cowboys should be able to walk on them and there be no problems.

 

[Randy in Maine]

4) attach pex to 6'' x 6'' 10ga. steel mesh sit on chairs and pour concrete slab

That is how I did mine also. No issues.

 

[rburke65]

Pex to wire mesh.

 

[pstnbly]

My understanding is the most efficient placement of the radiant tubing is in the bottom 1/3 of the slab. Coincidentally this is also the best placement for the reinforcing. We tie the PEX to the reinforcing (mesh or bar), then the steel is placed on plastic screw in chairs. Best way yet I have found.