Pole shed in floor heat

shop_kev

Message:
Hi, I have a 50x72 pole shed and was thiking about doing sand over the in floor heat tubes then pouring the concrete. Are there pros or cons to putting sand over the top of you heat tubes then pouring concrete?

EdTheHeaterMan

Insulation under the tubing is more important than anything. the closer the tubing is to the top of the concrete the better. that said, you don't want it too close where it could be damaged during construction or while the building is in use. Adding sand over the tubing than putting the concrete over the sand seems to be adding extra distance from the heat source to the heat emitter. (the floor surface). That said, if the insulation below the tubing is properly sealed so the sand will not find its way thru the cracks and increase conduction heat to migrate into the earth, then there is little consequence in using the sand. But if the insulation is not properly sealed, the direct pour on the concrete will not migrate thru the cracks once the concrete sets up.

GroundUp

Absolutely do not put sand over the tubing unless the surface is asphalt or pavers. Sand is an insulator more than anything, and will reduce efficiency of the system. Get the tubing embedded in the concrete, whether stapled on top of the foam or suspended toward the center of the slab. Closer to the surface will be more efficient than at the bottom, but sucks to install and I feel the gain is minimal in a regular 4-5" slab.

kcopp

Sand would suck... DON'T do it.... 2" of good EPS.

shop_kev

Thanks for the info, the thought for the sand was that incase of power outage or boiler problem it would hold the heat long and if down the road i would need to anchor anything to the floor i would not have to worry about hitting my heat tubes. 

Dave H_2

You don't want to put the tubes too close to the surface in this style of shop, the concrete right above the tube will not be strong enough for your equipment. A 4-6" slab with the tubing in the middle-ish area works great and gives the support you need.
Also a slab this thick and this large will hold onto the heat for a loooong time if there is a power outage. I have run into projects where after 5 days of no power, the place only dropped 10 degrees in air temp.
Of course that does depend upon how many times doors are opened and closed and such.

Also, when it comes to radiant slabs, the entire slab needs to heat up before BTU's start to leave the slab. Then the Law of Thermodynamics kicks in; heat goes to cold, always. The larger the temperature difference, the faster the rate of heat transfer unless something is in its way like insulation.

Remember, its the slab that is heating the space, not the tubing when it comes to placement in the slab.

Dave H.

Zman

Tubing in the middle of the slab is a good plan for your application. If you are worried about anchors and tubing, just pick up an inexpensive infrared camera and locate the tubing before you drill.
Dry sand is a horrible heat conductor, good insulation (particularly at the edges) and tubing in the slab is the way to go.

hot_rod

A full 4" slab is plenty unless you have very heavy equipment.

Sand only if you add portland cement and water to it

If it is in the budget, place the tube 6" on center. This allows the lowest possible supply temperature and ramps up quickly.