In Slab Radiant Heat

Meyers Farms

Meyers Farms

Active member
Just finished my new shop, it’s 40’x48’x16’. I’m currently working on the floor and plan to have in slab radiant heat. I put down a 6 mil plastic vapor barrier followed by 2” extruded polystyrene insulation. I am going to pour 6” thick concrete with steel in it. From what I’ve read it is inefficient to to attach the piping directly to the top of the insulation in a 6” slab bc it’s too far from the surface. What do you guys think? The other option is to suspend rebar and attach the piping to the rebar putting it closer to the surface but deep enough that it won’t be cut when cutting joints. If I attach to the insulation it will be easier to pour because I could use wire mesh and just pull it up as we poured. I’m afraid to attach the piping to wire mesh bc of it floating too high. Looking at doing 3/4” line on 12-14” centers with 300’ max per loop.

What’s your thoughts, any experience?
 
That's how they did mine. Attached right to the foam board. I have not got the floor running yet but was in a shop where it was done the same way and it was amazing. How do they figure it is inefficient? Once the floor is warm it stays warm. Even if you suspended it in the middle the heat is still going to go down towards the foam.
 
They make clips that will elevate the piping. I would go that route, also make sure the piping is far enough down from the surface so you don't worry about cutting into it when doing the control cuts.
 
When my parents built their house, the piping was attached to the mesh, but that was just the basement floor.

Once you work in a shop with radiant heat, it's hard to go back. I have been in a few shops that used it. It's amazing how quickly snow and water dry. We would park a tandem plow truck in after a run, the next morning the floor was dry, hardly a trace of moisture.
 
Mt shop is heated with Radiant floor heat. Tubes are clear on the bottom, on 6" slab, one 8" slab. You aren't heating anything but the slab, so I don't know if it matters where you put it. You DO NOT want it right on wire or rebar, as it can get messed up while pouring the slab.

So right against the insulation, or if putting down wire mesh, they make clips to bring it up a bit.

After it's done, set the thermostat and forget it. You don't want to mess with it much!
Chris
 
I'm in the same boat,just built a 36x40x14. Just finished digging down 2 foot around the perimeter and insulating it with 3.5"eps,which I would go back and do if you didnt.from what I read the majority of your heat loss is from not insulating the perimeter. What're you going to use to heat your water?edit I'm also stuck on how high to set the pex,I don't want to to high because like you said when you go to cut your lines you don't want to hit one.but the lower they are the more effecieny you lose.I'm also trying to figure out how I'm going to do this without destroying my pex because I concrete truck won't cross my bridge which means I'll have to use concrete buggies.and I figure concrete buggies will be awfully hard on that pex running over it
 
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Question for guys that do have it. So lets say you plan on putting a lift in, for discussion purposes, a 2 post lift. And you have to set your anchor's on posts, how do you go about doing this? Try and plan ahead of time and not lay out the tubing in these areas, or try and set anchors in slab ahead of pour? I just know this was a conversation when buddy was building his shop.
 
Smokinrebel said:
Question for guys that do have it. So lets say you plan on putting a lift in, for discussion purposes, a 2 post lift. And you have to set your anchor's on posts, how do you go about doing this? Try and plan ahead of time and not lay out the tubing in these areas, or try and set anchors in slab ahead of pour? I just know this was a conversation when buddy was building his shop.
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2 choices.1 turn the heat on and get a flir camera to see where the pex is,or 2 plan ahead and loop around where the baseplate's for the lift will be
 
thatguy69 said:
2 choices.1 turn the heat on and get a flir camera to see where the pex is,or 2 plan ahead and loop around where the baseplate's for the lift will be
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That doesn't work very well. Tried it. We have drilled into our tubes before, not good.


Only one good option, plan ahead. The other option is to pour the floor thick enough you don't have to worry about it.

Chris
 
Smokinrebel said:
Question for guys that do have it. So lets say you plan on putting a lift in, for discussion purposes, a 2 post lift. And you have to set your anchor's on posts, how do you go about doing this? Try and plan ahead of time and not lay out the tubing in these areas, or try and set anchors in slab ahead of pour? I just know this was a conversation when buddy was building his shop.
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I am glad you asked this because i was going to mention a few ways i have seen in the past to prevent this. The best method i have seen is very good strait lines in the tubing that run parallel to each other and a wall. You then take measurements and mark off on the wall where your center lines of the tubes are. Leave a feature or some type of starting point to measure from and then you can always calculate your lines. I have seen people set nails in the concrete on the center lines at the garage door side so they knew as well.

Depending on your local weather and how much "on the back" work you intend on doing in the shop, you may want to supplement with overhead radiant heating. In a large shop on a cold winters day it sucks to be on your back sweating while you are doing a crappy job under your machine. nicer to drop slab heat a touch and keep air warm with radiant heating. If you are just using it to dry floor and keep cars warm, no real concern.
 
Nootch said:
Depending on your local weather and how much "on the back" work you intend on doing in the shop, you may want to supplement with overhead radiant heating. In a large shop on a cold winters day it sucks to be on your back sweating while you are doing a crappy job under your machine. nicer to drop slab heat a touch and keep air warm with radiant heating. If you are just using it to dry floor and keep cars warm, no real concern.
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If you aren't working under cars or trucks, that isn't an issue. We work on large equipment here, and keep our slab temp about 72* to keep our air temp around 65*

Chris
 
Signature600 said:
That doesn't work very well. Tried it. We have drilled into our tubes before, not good.


Only one good option, plan ahead. The other option is to pour the floor thick enough you don't have to worry about it.

Chris
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Dam that sucks.how did you fix it or do you just run without that loop now?curious to how effecient it is to heat this way and what your using to heat your water
 
We just ran without it. Wasn't in our shop, in my dad's half assed pool building. Needs busted up so they can start over honestly, but that was 15 years ago now.

We use a waste oil boiler most of the time, but when it's really cold we have a Natural gas boiler we can supplement with. I heater with just the gas a few years ago when we were having oil boiler problems...I am heating 25,000 square feet, half 16' tall, half 24' tall...when we ran just the gas boiler it was around $1200/month...which I thought wasn't too bad considering it costs $400/month to heat 6400sq ft with 2 forced air furnaces.

Chris
 
Signature600 said:
That doesn't work very well. Tried it. We have drilled into our tubes before, not good.


Only one good option, plan ahead. The other option is to pour the floor thick enough you don't have to worry about it.

Chris
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Did you shut the heat off for 24+ hours and let it cool? I would think then if you fire it up, you should see the differential, unless the distance from the tube to the surface is more than the distance between tubes.
 
zstroken said:
Did you shut the heat off for 24+ hours and let it cool? I would think then if you fire it up, you should see the differential, unless the distance from the tube to the surface is more than the distance between tubes.
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Yes, we tried everything. Tried shutting off each tube individually, as it was only a few runs.

However, as I said, that was years ago. Maybe the thermal imaging is good enough now you can pull it off??

I would still recommend planning ahead instead of trying to cut holes in my floor heat.
Chris
 
Thanks for all of the responses! Also thank you to Chris for chiming in, I couldn't remember the specs of your shop. I will say it was very comfortable the extremely cold day we were in it. As far as my lift goes: I will be spacing the tubing out around the footprint of the anchor points. (moving lift from existing shop to new shop)

What do you guys think about my tubing size and spacing? 3/4" diameter tubing with max run of 300' at spacing of 12". Also forgot to mention in original post that the sides of the slab are insulated as well.
 
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Meyers Farms said:
Thanks for all of the responses! Also thank you to Chris for chiming in, I couldn't remember the specs of your shop. I will say it was very comfortable the extremely cold day we were in it. As far as my lift goes: I will be spacing the tubing out around the footprint of the anchor points. (moving lift from existing shop to new shop)

What do you guys think about my tubing size and spacing? 3/4" diameter tubing with max run of 300' at spacing of 12". Also forgot to mention in original post that the sides of the slab are insulated as well.
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Should be fine. I think my shops are all 5/8" tubing, same run length and spacing. One slab is insulated , one is not. You can feel a difference in the heat in each building.

Sounds like you'll have it set up right all around.

What is your heat source?
Chris
 
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