radiant floor in my shop

well my 40x60 pole barn is almost done going with radiant floor heat for sure what is best way to insulate before in pour the floor 4x8 foam sheets or the rolls of double bubble foil or is there something eles thanks cdv

I would do 2" builder grade foam and one side foil double double.

The sides of the slab are more important than under it. The earth is a pretty good insulator, if you get perimeter insulation well below the frost depth after a few years the soil under the slab will stay warm. The heat coming from the center of the earth is substantial and will warm the soil. We had one equipment building permitted in Prudhoe Bay to be built on grade. The air temperature in the building was kept about freezing, but heat from inside the earth, and the lack of cold winter air chilling the subsurface caused permafrost to melt under the building. They added a couple hundred tons of rock every year to keep the floor at ground level.

You have to do a really, really good job with your rough grade under ridgid foam. If you don't the foam will bridge and leave pockets, which will lead to cracks in your floor. There are products out there that are like concrete blankets that will follow any uneveness in your rough grade to support your floor better. I have seen instances where styrofoam was used, and very heavy point loads were in floors, (town hyw. plow trucks loaded with sand and heavy plows, that colapsed the styrofoam under the concrete.
You also need to pay perticular attention to floor drains, and how you route your radiant tubeing AROUND them.
You don't need an extreamly high R value under the floor, but it does need to have a very good vapor barrier. Moisture will wick away the heat without good vapor protection.
I am a retired contractor and built a good number of Ag and comercial steel buildings with radiant heat in them.
Also make sure you isolate the aprons with a vertical frost barier protruding to finish level, between floor and aprons, and string the tubing closer together in front of overhead doors. A good R 10+ vertical frost barier at least 2' deep, around the perimiter of the building is also necessary. We used 2" ridgid styrofoam there.
The tubeing in the pics is 7/8" supplied by Radiant Tech Inc., Lyndonville VT., who designed and provided materials and controls for our heating systems.
Loren, the Acg.

(quoted from post at 21:40:59 11/07/15) I have seen instances where styrofoam was used, and very heavy point loads were in floors, (town hyw. plow trucks loaded with sand and heavy plows, that colapsed the styrofoam under the concrete.
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Most people not in the trades assume that all foam is the same. The stuff you see at most home centers is only good for 15 or 25 PSI when used under a floor. The foam that is made for under commercial floors is rated at 40, 60, and 100 PSI. Obviously the price goes up accordingly, so some may be tempted to cheap out on the foam.

The last building I had radiant done in was a DOT truck shop. We used 2 staggered layers of 2" 60PSI foam. Radiant tubing was stapled to the foam and then 4" of washed sand went in to cushion and separate the tubing from the concrete.

ACG has the best reply, but it would be best to go to heatinghelp.com and post this question on "the wall" so more professionals can answer you. The edge insulation is really important, or you will be heating "the world". A second opinion would only take a few minutes..

When I built mine the company that I bought the PEX from recommended double foil backed for the floor. Silver side up to reflect the heat up and stop it from going down. Right or wrong, that is the way I did it. I have never heated the building but I can!

Insulation under your floor and around the wall if very important. You will be heating the world. I like the products that Aqua Therm in Mn. offers. Plus lots of advise and know how.

I have seen a job where they used a gravel pad covered with spray foam. Over top of that went went a couple inches of sand then wire mesh with tubing ties to it,concrete over that. It's about a 50x80 w 16 foot ceilings. The owner told me how itvwas biult when I was fixing his econo-burn wood boiler. He keeps the whole thing 70?. I had to wait for overnight delivery of a new control board. I know for fact he had no heat source for 24 hrs and he only lost 10? of his space temperature. Guy also says 4 cords of hardwood will take care of him for the year.

The foil bubble wrap has two shortcomings: It won't support any weight and it has almost zero insulating value. Forget about using that stuff.

You need to use 40 psi minimum foam planks over a well-compacted base if you're going to put anything heavy on your floor. The stuff from the big box stores is weaker than that, so you'll have to look around for the good stuff.

I insulated the floor of my shop and put in tubing, but I haven't finished the ceiling yet. So I haven't hooked up the radiant heat and can't report on how well it heats, but I have NO CRACKS in my floor ten years after it was poured. Here's how I did mine:

The insides of the skirt boards are insulated with 2" foam board. I beveled the upper edge of the foam plank so the concrete runs all the way to the skirt board, but that's not really necessary since the inner walls would have covered the exposed board everywhere but the doorway.

The first eight feet of floor adjacent to the walls has two inch insulation for a five inch concrete depth. The rest of the floor, including the doorway of the overhead door, has one inch insulation for a six inch thick floor.

The floor has wire mesh in it, although I might use rebar if I was to do it again. Wherever I planned to put a saw cut, I cut every other strand in the mesh to weaken it. The tubing is inside a short conduit wherever it passes through a saw cut to protect it from damage when the concrete cracks.

To prevent heat loss through the overhead doorway, I put in a pressure-treated 2x6 right where the door will close, and glued a beveled plank of insulation to the inside of the 2x6.

Here is a product that I've seen advertised but I have no experience with it. Sounds and looks good as it is an insulator, a barrier and a guide for laying the tubing:

http://www.hotrockpanels.com/products/

Don't really need insulation just a thermal break between ground and slab. Also the outside and slab.I used 1" slab foam and heat a 30 x 48 x 15 shop with a water heater. Works fine. Have cellulose insulation in ceiling which is the most important thing you can do. Heat rises.