# Thread: Floor heating

1. ## Floor heating

I think In February I’ll be redoing the kids bathroom. Since we spend the same amount of time in it as they do, I want my feet warm. Problem is we’re on a slab, so can’t use 1/2 inch pex then put my tile down as they would put me a considerable height above the adjoining floor.

The question is, would 1/4 in pipe work and provide enough heat for comfort only? The area that would be heated is 3’x12’. My thought was to run a 1/2” line then split it to 3 1/4” inch lines. Run each 1/4” loop 12” wide by the length of the room. Thoughts if it would provide any heat. I’m not a radiant guy.

Clearly the other option is electric, but I did that in my last house and even with a 220 feed it made the meter spin.

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You suppliers sales engineer should be able to lay everything out. I would imagine you could do something with 5/16 or ⅜ pex. I never heard of ¼ radiant pex

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3. Originally Posted by jbhenergy
I think In February I’ll be redoing the kids bathroom. Since we spend the same amount of time in it as they do, I want my feet warm. Problem is we’re on a slab, so can’t use 1/2 inch pex then put my tile down as they would put me a considerable height above the adjoining floor.

The question is, would 1/4 in pipe work and provide enough heat for comfort only? The area that would be heated is 3’x12’. My thought was to run a 1/2” line then split it to 3 1/4” inch lines. Run each 1/4” loop 12” wide by the length of the room. Thoughts if it would provide any heat. I’m not a radiant guy.

Clearly the other option is electric, but I did that in my last house and even with a 220 feed it made the meter spin.

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Without insulation most of the heat will go into the earth under the slab!

How thick is that slab? 10' X 10' area cuts real easy but is messy.

4. Originally Posted by Spitz
You suppliers sales engineer should be able to lay everything out. I would imagine you could do something with 5/16 or ⅜ pex. I never heard of ¼ radiant pex

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Yeah 1/4” may not exist I honestly haven’t put a lick of research into it yet. Figured I would ask the brain trust here first before moving forward.

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Originally Posted by pecmsg
Without insulation most of the heat will go into the earth under the slab!

How thick is that slab? 10' X 10' area cuts real easy but is messy.
X2,,,, now having a warmish foot(don't that feel good) is one thing and satisfying a heat load is another thing.

6. In that situation I would:

Option 1 - cut the slab inside the bathroom walls into 12" square blocks and carry them out. Remove soil to about a 12" depth and tamp in a bed of crushed concrete. Lay on a sheet of EDPM as a vapor and put 4" of high quality foam board over it. Edge-drill the existing slab all around, install 1/2" rebar on 12" centers and tie all the 1/2" pex to the rebar grid. Then coat the edge of the old slab with concrete adhesive and pour the new floor. I would want to keep the new concrete wet for 28 days - but a week would be strong enough I imagine and/or you could use a high-early mix to shorten the cure time.

Option 2 - install a large vanity rather than a pedestal and build a 4" false-floor into the closet. Install three kick space heaters under the vanity (left, right, and center) and two under the closet. Direct one of them to heat under the tub. Supply them with boiler water as a separate zone or with a loop off the domestic water heater.

PHM
---------

Originally Posted by jbhenergy
I think In February I’ll be redoing the kids bathroom. Since we spend the same amount of time in it as they do, I want my feet warm. Problem is we’re on a slab, so can’t use 1/2 inch pex then put my tile down as they would put me a considerable height above the adjoining floor.

The question is, would 1/4 in pipe work and provide enough heat for comfort only? The area that would be heated is 3’x12’. My thought was to run a 1/2” line then split it to 3 1/4” inch lines. Run each 1/4” loop 12” wide by the length of the room. Thoughts if it would provide any heat. I’m not a radiant guy.

Clearly the other option is electric, but I did that in my last house and even with a 220 feed it made the meter spin.

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7. Originally Posted by Poodle Head Mikey
In that situation I would:

Option 1 - cut the slab inside the bathroom walls into 12" square blocks and carry them out. Remove soil to about a 12" depth and tamp in a bed of crushed concrete. Lay on a sheet of EDPM as a vapor and put 4" of high quality foam board over it. Edge-drill the existing slab all around, install 1/2" rebar on 12" centers and tie all the 1/2" pex to the rebar grid. Then coat the edge of the old slab with concrete adhesive and pour the new floor. I would want to keep the new concrete wet for 28 days - but a week would be strong enough I imagine and/or you could use a high-early mix to shorten the cure time.

Option 2 - install a large vanity rather than a pedestal and build a 4" false-floor into the closet. Install three kick space heaters under the vanity (left, right, and center) and two under the closet. Direct one of them to heat under the tub. Supply them with boiler water as a separate zone or with a loop off the domestic water heater.

PHM
---------
Good lord Mikey I’m looking at 4 days not 4 months lol.

I realize under the heat should be insulated as I did on my last house and electric floor heat but I’m willing to absorb that loss in this case.

Now that you guys are making me think about this I figured I would have to look stuff up. 3/8 pex is 1/2 od so plus a bit of grout on top I’m probably looking at adding 5/8 to the floor thickness. I’m sure I can find some transition to adjust for that 5/8 thickness addition.

And since it’s really only for comfort during bath time and what not, I’ll eat that loss just for the pure comfort effect.

Hell maybe if the wife likes it enough I’ll get lucky the week after it’s installed.

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8. Originally Posted by jbhenergy

Hell maybe if the wife likes it enough I’ll get lucky the week after it’s installed.

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Get that agreement up front

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How about radiant in the ceiling? You'll only lose 1 1/4"

10. You could saw cut/notch the existing slab and lose no height at all.

11. Originally Posted by STEVEusaPA
How about radiant in the ceiling? You'll only lose 1 1/4"
I’m going for warm feet. Tile is cold in the winter on my old body.

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12. Originally Posted by Poodle Head Mikey
You could saw cut/notch the existing slab and lose no height at all.
They make some slick attachments for angle grinders that all but eliminates the dust. I have thought of the option of doing that. Not ruled it out completely at this point.

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Just lay down electric infloor and only use it when you are in there. Put it on a timer so it's not left on.

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