akpolaris
Well-known member
Does anyone have an info on laying a layer of sand on the radiant heat loops in a cement floor. Supposed to heat the sand helping to heat the cement more evenly. It is all on top of the insulation layer of course
Bedding radiant tubes heat in sand
- Thread starter akpolaris
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The more mass the floor has the slower it is to respond -- and the more BTU's.
Some concrete guys like to use sand because it makes doing the slab easier.
The best way to achieve an even floor temp is to use enough tubing -- spaced correctly.
I like to run the hot leg towards the exterior walls and make the returns toward the center.
Some concrete guys like to use sand because it makes doing the slab easier.
The best way to achieve an even floor temp is to use enough tubing -- spaced correctly.
I like to run the hot leg towards the exterior walls and make the returns toward the center.
Rookie2
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I'd stay away from that. If it isn't recommended in a pex heating manual ,stick with known design plans. (Wirsbo) etc.
dewalt378g
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I believe they make plastic chairs you can use for your tubing so you can lay it up in your slab exactly where you want it.
theoldwizard1
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The "typical installation" is tieing the PEX to a wire grid which may or may not be raised on :chairs" to keep it in the middle of the slab.
dewalt378g
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Rookie2
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I concentrated loops at the garage door and perimeter. 6" loops at outside walls down to 24" loops in the center of the building. works great. no instant on heater will work because the floor gives up heat slowly and warms up slowly.
CARS
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Never understood how they do that. Do the guys pouring the slab float around using pixie dust or jet packs?
Around here the guys put on boots and get into it. They pull the reinforcement up as they pour.
dewalt378g
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You can walk on them. Same techniques are used almost everywhere. Some don't like pulling the mesh/bar, some do , some don't care, sometimes it's speced out that the reinforcement must be in the middle (as it normally should). Either way you look at it, using chairs does a better job. With the fuel prices these days I prefer the pixie dust.
What about cutting up a bunch of the 2" styrofoam into 2x2x2 blocks and placing them at the intersections of the wire mesh, say on a 2'x2' grid? Rip on a table saw. This is my first post, doing a 650 sf walk out basement studio with fireplace. 7 kw elc. Boiler Electro ind. EMB-S7. PATC with 3.5 KW heat and 15100 BTU AC. Manards close loop panel. On the shores of Lake Huron Michigan , 10 miles North of Port Sanalic.
This is a great site
This is a great site
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Randy in Maine
Well-known member
No. Keep in mind that you are just sending out 120º water out to the concrete from the heat source and it will come back to the heat source at about 90º.
If I lived in AK, I would use 3 or 4" of insulation under the concrete to keep heat out of the permafrost. What do the locals around you do?
anthony666
Well-known member
funny you should say that, it is one of the options in the wirsbo design manual
koditten
Well-known member
I saw no meantion of insulation under the slab, please tell me you were at least going to do that.
Information form local contractors is what promoted my question regarding the sand. The layer of sand is above the foam insulation. I heard of it from 1 of the batch plant operators. I intend to discuss it with some guys that install the systems before I move forward next spring
koditten
Well-known member
What would be the difference between embedding the pex in concrete vs sand? I'm thinking no difference.
I think dealing with the sand would just be a waste of time. I am interested in what the pro's say.
KO
I think dealing with the sand would just be a waste of time. I am interested in what the pro's say.
KO
Concrete guys would rather pour over sand so their mud will set quicker and they're not still finishing it at midnight.
Sand is going to have some insulation properties but with foam below the heat will go up eventually.
As an HVAC guy I want the tube tied to mesh sitting on chairs, concrete guys only have yo deal with it one day, I have to deal with it for many years.
Sand is going to have some insulation properties but with foam below the heat will go up eventually.
As an HVAC guy I want the tube tied to mesh sitting on chairs, concrete guys only have yo deal with it one day, I have to deal with it for many years.
When you build a solar radiant house you want/need a storage space for the excess heat produced during the day -- years ago people installed sand. It would take all day to heat up and give you heat in the evening and night ... that was the theory. I never heard if it really working. Now they use a water storage tank.
The guys that use sand today do it to make the concrete job easy .. not to make a good radiant system. It can cause all kinds of problems.
The best radiant systems are not "high mass" and concrete is high mass. The greater the mass the more BTU's required and the slower it is to respond. You see radiant used in concrete because? Without it the concerete is cold.
The only place thick slabs are a plus -- industrial space that has huge doors opening all the time.
The more insulation and the closer you can get the tubes to the surface the better. Having sand around the tubes is going to reduce the BTU's that can be transferred from the hot water.
You don't want sand.
The guys that use sand today do it to make the concrete job easy .. not to make a good radiant system. It can cause all kinds of problems.
The best radiant systems are not "high mass" and concrete is high mass. The greater the mass the more BTU's required and the slower it is to respond. You see radiant used in concrete because? Without it the concerete is cold.
The only place thick slabs are a plus -- industrial space that has huge doors opening all the time.
The more insulation and the closer you can get the tubes to the surface the better. Having sand around the tubes is going to reduce the BTU's that can be transferred from the hot water.
You don't want sand.
The last 2 were the most informative responses, thank you. Brewchief I see you are also from a cold climate and HVAC guy. How do you deal with it for years?? What is your opinion on using a Toyo boiler vs a on demand water heater that supplies the domestic water needs as well as the radiant heat? I have a 32' X 32' shop with 16' walls, 6" slab with radiant heat. The plan is building an apartment 12' X 32' (mezzanine) in there as well.
tdkkart
Well-known member
"Dealing with it for years", as in if you take bad advice, or let someone do it wrong, you will be dealing with a poorly operating system forever, especially if the mistake is made in or under the slab
Even though thousands of installations use on demand heaters successfully, and many manufacturers approve their demand heaters for space heating, the "experts" will tell you it can't or shouldn't be done. Hot water is hot water, really doesn't matter where you get it from as long as the source has the capacity to deliver it at a reasonable efficiency.
If we install a job improperly or use inferior materials we will have to deal with warranty call backs and an unhappy customer for years to come, I have customers that I have dealt with for over 15 years.
I personally prefer using a boiler for heating and a separate source for domestic hot water, I don't like all my eggs in one basket. Using one unit for both can work if the system is designed properly.
I am still planning, won't pour the floor till next summer, I think. Doing as much research and asking questions of professionals. If the sand helps the mud set up and does not negatively affect the heating it may not be a bad idea. I do prefer the separate systems concept.
Randy in Maine
Well-known member
My understanding is that the sand is provide for additional thermal mass if it was indeed needed for a design requirement.
For example, I considered doing it when I converted an existing garage slab into a finished room. I was going to put in 2x6 sleepers on the existing slab, fill it with sand and pex tubing, and then put a wooden floor over it.
I instead opted to put down 1" of foam insulation and 3 1/2" of concrete with the pex with ceramic tile on the top of it.
For example, I considered doing it when I converted an existing garage slab into a finished room. I was going to put in 2x6 sleepers on the existing slab, fill it with sand and pex tubing, and then put a wooden floor over it.
I instead opted to put down 1" of foam insulation and 3 1/2" of concrete with the pex with ceramic tile on the top of it.
putting sand around pex would insulate it.
thermal conductivity of:
concrete = .40 to .70
sand = .15 to .25
mineral wool = .04
foam + .03
i'm not sure if anyone has tried it, but if you couldn't afford 2" of foam under your concrete, put 12" of dry sand and make sure your pex is in your concrete.
thermal conductivity of:
concrete = .40 to .70
sand = .15 to .25
mineral wool = .04
foam + .03
i'm not sure if anyone has tried it, but if you couldn't afford 2" of foam under your concrete, put 12" of dry sand and make sure your pex is in your concrete.
ford33
Well-known member
Here is an interesting article from Fine Homebuilding about insulating garage slabs with and without radiant heat.
http://www.finehomebuilding.com/item/15902/how-to-pour-a-rock-solid-well-insulated-garage-slab/page/all
http://www.finehomebuilding.com/item/15902/how-to-pour-a-rock-solid-well-insulated-garage-slab/page/all